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How to read OleDbSchemaGuid tables 1 record at a time ?if we have an OleDbConnection it is possible to retrieve a datatable containing information about the database fields using the statement (watch out line breaking): OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, New Object() {}) This however return a whole DataTable, which in some cases can be very large. For instance if you do it with SAP you receive over half million rows. My question: I would like to do the same operation programmatically and not using the statement GetOleDbSchemaTable. Possibly taking 1 record at a time, similarly to the DataReader mechanism. Can anyone suggest how to achieve that? -Tom You can pass an array of filter values as a last parameter.
-- Show quoteMiha Markic [MVP C#, INETA Country Leader for Slovenia] RightHand .NET consulting & development www.rthand.com Blog: http://cs.rthand.com/blogs/blog_with_righthand/ <tommaso.gasta***@uniroma1.it> wrote in message news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > Hi, > > if we have an OleDbConnection it is possible to retrieve a datatable > containing information about the database fields using the statement > (watch out line breaking): > > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > New Object() {}) > > This however return a whole DataTable, which in some cases can be very > large. For instance if you do it with SAP you receive over half million > rows. > > My question: > > I would like to do the same operation programmatically and not using > the statement GetOleDbSchemaTable. Possibly taking 1 record at a time, > similarly to the DataReader mechanism. > > Can anyone suggest how to achieve that? > > -Tom > Of course Miha, but I was talking about processing rows (not fields).
It's clear that one can select columns passing an argument to GetOleDbSchemaTable. My question was another: I want a programmatic substitute of GetOleDbSchemaTable that allows me to consider 1 record at a time. Thank you for your reply. -Tom Miha Markic [MVP C#] ha scritto: Show quote > You can pass an array of filter values as a last parameter. > > -- > Miha Markic [MVP C#, INETA Country Leader for Slovenia] > RightHand .NET consulting & development www.rthand.com > Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > <tommaso.gasta***@uniroma1.it> wrote in message > news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > Hi, > > > > if we have an OleDbConnection it is possible to retrieve a datatable > > containing information about the database fields using the statement > > (watch out line breaking): > > > > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > New Object() {}) > > > > This however return a whole DataTable, which in some cases can be very > > large. For instance if you do it with SAP you receive over half million > > rows. > > > > My question: > > > > I would like to do the same operation programmatically and not using > > the statement GetOleDbSchemaTable. Possibly taking 1 record at a time, > > similarly to the DataReader mechanism. > > > > Can anyone suggest how to achieve that? > > > > -Tom > > ....And just loop through the rows using the DataTable.Rows collection (it
would interesting to check if restrictions are applied on the result or are processed server side for your DB). Else if you want really a replacement you'll have to use specific statements for this (for example for SQL Server you could use the information_schema.columns view or the appropriate stored procedures). -- Show quotePatrice <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > Of course Miha, but I was talking about processing rows (not fields). > It's clear that one > can select columns passing an argument to GetOleDbSchemaTable. > > My question was another: I want a programmatic substitute of > GetOleDbSchemaTable > that allows me to consider 1 record at a time. > > Thank you for your reply. > > -Tom > > Miha Markic [MVP C#] ha scritto: > >> You can pass an array of filter values as a last parameter. >> >> -- >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] >> RightHand .NET consulting & development www.rthand.com >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ >> >> <tommaso.gasta***@uniroma1.it> wrote in message >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... >> > Hi, >> > >> > if we have an OleDbConnection it is possible to retrieve a datatable >> > containing information about the database fields using the statement >> > (watch out line breaking): >> > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, >> > New Object() {}) >> > >> > This however return a whole DataTable, which in some cases can be very >> > large. For instance if you do it with SAP you receive over half million >> > rows. >> > >> > My question: >> > >> > I would like to do the same operation programmatically and not using >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a time, >> > similarly to the DataReader mechanism. >> > >> > Can anyone suggest how to achieve that? >> > >> > -Tom >> > > Hi Patrice. Thanks... Hmmm,
it seems I really have problem with my English :) Sorry! It's clear that - once one has a DataTable - one can read a row at a time. What I was trying to explain is that I do not want to get the whole DataTable, but just get one record at a time. This would be the same difference between: DataAdapter + Fill() [gets the whole table at a time] DataReader + Read() [gets 1 record at a time] I would like to know how to implement something similar to the DataReader + Read() schema for OleDbSchemaGuid tables. And I want it works for any OleDb connection (independently of the DBMS) I hope now it is more clear my goal. Thank you! Patrice ha scritto: Show quote > ...And just loop through the rows using the DataTable.Rows collection (it > would interesting to check if restrictions are applied on the result or are > processed server side for your DB). > > Else if you want really a replacement you'll have to use specific statements > for this (for example for SQL Server you could use the > information_schema.columns view or the appropriate stored procedures). > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > Of course Miha, but I was talking about processing rows (not fields). > > It's clear that one > > can select columns passing an argument to GetOleDbSchemaTable. > > > > My question was another: I want a programmatic substitute of > > GetOleDbSchemaTable > > that allows me to consider 1 record at a time. > > > > Thank you for your reply. > > > > -Tom > > > > Miha Markic [MVP C#] ha scritto: > > > >> You can pass an array of filter values as a last parameter. > >> > >> -- > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > >> RightHand .NET consulting & development www.rthand.com > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > >> > >> <tommaso.gasta***@uniroma1.it> wrote in message > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > >> > Hi, > >> > > >> > if we have an OleDbConnection it is possible to retrieve a datatable > >> > containing information about the database fields using the statement > >> > (watch out line breaking): > >> > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > >> > New Object() {}) > >> > > >> > This however return a whole DataTable, which in some cases can be very > >> > large. For instance if you do it with SAP you receive over half million > >> > rows. > >> > > >> > My question: > >> > > >> > I would like to do the same operation programmatically and not using > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a time, > >> > similarly to the DataReader mechanism. > >> > > >> > Can anyone suggest how to achieve that? > >> > > >> > -Tom > >> > > > But why would you want to?
There is no significant gain.... -- Miha Markic [MVP C#, INETA Country Leader for Slovenia] RightHand .NET consulting & development www.rthand.com Blog: http://cs.rthand.com/blogs/blog_with_righthand/ <tommaso.gasta***@uniroma1.it> wrote in message news:1152019369.810484.36180@m79g2000cwm.googlegroups.com... Hi Patrice. Thanks... Hmmm,it seems I really have problem with my English :) Sorry! It's clear that - once one has a DataTable - one can read a row at a time. What I was trying to explain is that I do not want to get the whole DataTable, but just get one record at a time. This would be the same difference between: DataAdapter + Fill() [gets the whole table at a time] DataReader + Read() [gets 1 record at a time] I would like to know how to implement something similar to the DataReader + Read() schema for OleDbSchemaGuid tables. And I want it works for any OleDb connection (independently of the DBMS) I hope now it is more clear my goal. Thank you! Patrice ha scritto: Show quote > ...And just loop through the rows using the DataTable.Rows collection (it > would interesting to check if restrictions are applied on the result or > are > processed server side for your DB). > > Else if you want really a replacement you'll have to use specific > statements > for this (for example for SQL Server you could use the > information_schema.columns view or the appropriate stored procedures). > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > Of course Miha, but I was talking about processing rows (not fields). > > It's clear that one > > can select columns passing an argument to GetOleDbSchemaTable. > > > > My question was another: I want a programmatic substitute of > > GetOleDbSchemaTable > > that allows me to consider 1 record at a time. > > > > Thank you for your reply. > > > > -Tom > > > > Miha Markic [MVP C#] ha scritto: > > > >> You can pass an array of filter values as a last parameter. > >> > >> -- > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > >> RightHand .NET consulting & development www.rthand.com > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > >> > >> <tommaso.gasta***@uniroma1.it> wrote in message > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > >> > Hi, > >> > > >> > if we have an OleDbConnection it is possible to retrieve a datatable > >> > containing information about the database fields using the statement > >> > (watch out line breaking): > >> > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > >> > New Object() {}) > >> > > >> > This however return a whole DataTable, which in some cases can be > >> > very > >> > large. For instance if you do it with SAP you receive over half > >> > million > >> > rows. > >> > > >> > My question: > >> > > >> > I would like to do the same operation programmatically and not using > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > >> > time, > >> > similarly to the DataReader mechanism. > >> > > >> > Can anyone suggest how to achieve that? > >> > > >> > -Tom > >> > > > English is not may native language either. I should just have been more
explicit. This is the second part then. Use a custom replacement for you DBMS with a DataReader (note that a DataReader still uses a buffer). What I wanted to convey with the first part is that the problem lloks like to me that that you get all data at once. With restrictions (as suggested by Miha) you can get only those you are interested using a limited amount of memory. Though you may want to check that restrictions are processed server side it looks like quite a good solution. -- Show quotePatrice <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: 1152019369.810484.36***@m79g2000cwm.googlegroups.com... Hi Patrice. Thanks... Hmmm, it seems I really have problem with my English :) Sorry! It's clear that - once one has a DataTable - one can read a row at a time. What I was trying to explain is that I do not want to get the whole DataTable, but just get one record at a time. This would be the same difference between: DataAdapter + Fill() [gets the whole table at a time] DataReader + Read() [gets 1 record at a time] I would like to know how to implement something similar to the DataReader + Read() schema for OleDbSchemaGuid tables. And I want it works for any OleDb connection (independently of the DBMS) I hope now it is more clear my goal. Thank you! Patrice ha scritto: > ...And just loop through the rows using the DataTable.Rows collection (it > would interesting to check if restrictions are applied on the result or > are > processed server side for your DB). > > Else if you want really a replacement you'll have to use specific > statements > for this (for example for SQL Server you could use the > information_schema.columns view or the appropriate stored procedures). > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > Of course Miha, but I was talking about processing rows (not fields). > > It's clear that one > > can select columns passing an argument to GetOleDbSchemaTable. > > > > My question was another: I want a programmatic substitute of > > GetOleDbSchemaTable > > that allows me to consider 1 record at a time. > > > > Thank you for your reply. > > > > -Tom > > > > Miha Markic [MVP C#] ha scritto: > > > >> You can pass an array of filter values as a last parameter. > >> > >> -- > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > >> RightHand .NET consulting & development www.rthand.com > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > >> > >> <tommaso.gasta***@uniroma1.it> wrote in message > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > >> > Hi, > >> > > >> > if we have an OleDbConnection it is possible to retrieve a datatable > >> > containing information about the database fields using the statement > >> > (watch out line breaking): > >> > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > >> > New Object() {}) > >> > > >> > This however return a whole DataTable, which in some cases can be > >> > very > >> > large. For instance if you do it with SAP you receive over half > >> > million > >> > rows. > >> > > >> > My question: > >> > > >> > I would like to do the same operation programmatically and not using > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > >> > time, > >> > similarly to the DataReader mechanism. > >> > > >> > Can anyone suggest how to achieve that? > >> > > >> > -Tom > >> > > > Dear Miha , Patrice, ... and all
the advantage of having a mechanism similar to DataReader is obvious. Assume I am getting only the very first field of the COLUMN schema table. If I connect to SAP and run the GetOleDbSchemaTable command I get a datatable with 1 field and over half million rows. I would like to get 1 value at a time to process it instead of holding over half million values in memory at the same time, which I do not need. Further I usually need to take and process many more columns at the same time and the size of the datatable become enormous. Of course with small systems this is not a big problem. But try to work with real world databases... -tom Patrice ha scritto: Show quote > English is not may native language either. I should just have been more > explicit. > > This is the second part then. Use a custom replacement for you DBMS with a > DataReader (note that a DataReader still uses a buffer). > > What I wanted to convey with the first part is that the problem lloks like > to me that that you get all data at once. With restrictions (as suggested by > Miha) you can get only those you are interested using a limited amount of > memory. Though you may want to check that restrictions are processed server > side it looks like quite a good solution. > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > Hi Patrice. Thanks... Hmmm, > it seems I really have problem with my English :) Sorry! > > It's clear that - once one has a DataTable - one can read a > row at a time. > > What I was trying to explain is that I do not want to get the > whole DataTable, but just get one record at a time. > > This would be the same difference between: > > DataAdapter + Fill() [gets the whole table at a time] > DataReader + Read() [gets 1 record at a time] > > I would like to know how to implement something > similar to the DataReader + Read() schema > > for OleDbSchemaGuid tables. And I want it works > for any OleDb connection (independently of the DBMS) > > I hope now it is more clear my goal. > > Thank you! > > > > Patrice ha scritto: > > > ...And just loop through the rows using the DataTable.Rows collection (it > > would interesting to check if restrictions are applied on the result or > > are > > processed server side for your DB). > > > > Else if you want really a replacement you'll have to use specific > > statements > > for this (for example for SQL Server you could use the > > information_schema.columns view or the appropriate stored procedures). > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > Of course Miha, but I was talking about processing rows (not fields). > > > It's clear that one > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > My question was another: I want a programmatic substitute of > > > GetOleDbSchemaTable > > > that allows me to consider 1 record at a time. > > > > > > Thank you for your reply. > > > > > > -Tom > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > >> You can pass an array of filter values as a last parameter. > > >> > > >> -- > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > >> RightHand .NET consulting & development www.rthand.com > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > >> > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > >> > Hi, > > >> > > > >> > if we have an OleDbConnection it is possible to retrieve a datatable > > >> > containing information about the database fields using the statement > > >> > (watch out line breaking): > > >> > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > >> > New Object() {}) > > >> > > > >> > This however return a whole DataTable, which in some cases can be > > >> > very > > >> > large. For instance if you do it with SAP you receive over half > > >> > million > > >> > rows. > > >> > > > >> > My question: > > >> > > > >> > I would like to do the same operation programmatically and not using > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > > >> > time, > > >> > similarly to the DataReader mechanism. > > >> > > > >> > Can anyone suggest how to achieve that? > > >> > > > >> > -Tom > > >> > > > > You have basically two options :
1) Even with GetOleDbSchemaTable you *don't* have to read all columns. With the "restrictions" parameter, you are able to retrieve the columns for THE table you want. The table name is in third position. (or it could be not supported by SAP, also it's strange to me that you have only 1 field in the resulting DataTable, I would expect at least both the column name and the data type) 2) Else you can issue a custom statement to query for schema information. then you'll be able to use a DataReader (but you'll loose OleDB independance as you asked). To make it clear, even with #1 there is nothing that forces you to read half million rows. You just read the columns for the table you are currently interested in before fetching data for the next table. Try : OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns,New Object() {null,null,"<TableName>"}) I gave this a try with SQL Server and it worked fine (and yes restrictions are processed server side, the SP used just ask data for this table). Hopes it's clearer now. (do you access SAP data through some kind of specific driver or do you just use the driver for the underlying database, could it be a driver limitation ?) -- Show quotePatrice <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: 1152024828.274193.169***@p79g2000cwp.googlegroups.com... Dear Miha , Patrice, ... and all the advantage of having a mechanism similar to DataReader is obvious. Assume I am getting only the very first field of the COLUMN schema table. If I connect to SAP and run the GetOleDbSchemaTable command I get a datatable with 1 field and over half million rows. I would like to get 1 value at a time to process it instead of holding over half million values in memory at the same time, which I do not need. Further I usually need to take and process many more columns at the same time and the size of the datatable become enormous. Of course with small systems this is not a big problem. But try to work with real world databases... -tom Patrice ha scritto: > English is not may native language either. I should just have been more > explicit. > > This is the second part then. Use a custom replacement for you DBMS with a > DataReader (note that a DataReader still uses a buffer). > > What I wanted to convey with the first part is that the problem lloks like > to me that that you get all data at once. With restrictions (as suggested > by > Miha) you can get only those you are interested using a limited amount of > memory. Though you may want to check that restrictions are processed > server > side it looks like quite a good solution. > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > Hi Patrice. Thanks... Hmmm, > it seems I really have problem with my English :) Sorry! > > It's clear that - once one has a DataTable - one can read a > row at a time. > > What I was trying to explain is that I do not want to get the > whole DataTable, but just get one record at a time. > > This would be the same difference between: > > DataAdapter + Fill() [gets the whole table at a time] > DataReader + Read() [gets 1 record at a time] > > I would like to know how to implement something > similar to the DataReader + Read() schema > > for OleDbSchemaGuid tables. And I want it works > for any OleDb connection (independently of the DBMS) > > I hope now it is more clear my goal. > > Thank you! > > > > Patrice ha scritto: > > > ...And just loop through the rows using the DataTable.Rows collection > > (it > > would interesting to check if restrictions are applied on the result or > > are > > processed server side for your DB). > > > > Else if you want really a replacement you'll have to use specific > > statements > > for this (for example for SQL Server you could use the > > information_schema.columns view or the appropriate stored procedures). > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > Of course Miha, but I was talking about processing rows (not fields). > > > It's clear that one > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > My question was another: I want a programmatic substitute of > > > GetOleDbSchemaTable > > > that allows me to consider 1 record at a time. > > > > > > Thank you for your reply. > > > > > > -Tom > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > >> You can pass an array of filter values as a last parameter. > > >> > > >> -- > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > >> RightHand .NET consulting & development www.rthand.com > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > >> > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > >> > Hi, > > >> > > > >> > if we have an OleDbConnection it is possible to retrieve a > > >> > datatable > > >> > containing information about the database fields using the > > >> > statement > > >> > (watch out line breaking): > > >> > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > >> > New Object() {}) > > >> > > > >> > This however return a whole DataTable, which in some cases can be > > >> > very > > >> > large. For instance if you do it with SAP you receive over half > > >> > million > > >> > rows. > > >> > > > >> > My question: > > >> > > > >> > I would like to do the same operation programmatically and not > > >> > using > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > > >> > time, > > >> > similarly to the DataReader mechanism. > > >> > > > >> > Can anyone suggest how to achieve that? > > >> > > > >> > -Tom > > >> > > > > Wow, that's big.
Well, I still suggest you to do filtering and process the small amount of rows. As another solution, Patrice already mentioned, do execute proper sql statments to query the database metadata and you will have full control. Of course, it is database specific then. -- Miha Markic [MVP C#, INETA Country Leader for Slovenia] RightHand .NET consulting & development www.rthand.com Blog: http://cs.rthand.com/blogs/blog_with_righthand/ <tommaso.gasta***@uniroma1.it> wrote in message news:1152024828.274193.169670@p79g2000cwp.googlegroups.com... Dear Miha , Patrice, ... and allthe advantage of having a mechanism similar to DataReader is obvious. Assume I am getting only the very first field of the COLUMN schema table. If I connect to SAP and run the GetOleDbSchemaTable command I get a datatable with 1 field and over half million rows. I would like to get 1 value at a time to process it instead of holding over half million values in memory at the same time, which I do not need. Further I usually need to take and process many more columns at the same time and the size of the datatable become enormous. Of course with small systems this is not a big problem. But try to work with real world databases... -tom Patrice ha scritto: Show quote > English is not may native language either. I should just have been more > explicit. > > This is the second part then. Use a custom replacement for you DBMS with a > DataReader (note that a DataReader still uses a buffer). > > What I wanted to convey with the first part is that the problem lloks like > to me that that you get all data at once. With restrictions (as suggested > by > Miha) you can get only those you are interested using a limited amount of > memory. Though you may want to check that restrictions are processed > server > side it looks like quite a good solution. > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > Hi Patrice. Thanks... Hmmm, > it seems I really have problem with my English :) Sorry! > > It's clear that - once one has a DataTable - one can read a > row at a time. > > What I was trying to explain is that I do not want to get the > whole DataTable, but just get one record at a time. > > This would be the same difference between: > > DataAdapter + Fill() [gets the whole table at a time] > DataReader + Read() [gets 1 record at a time] > > I would like to know how to implement something > similar to the DataReader + Read() schema > > for OleDbSchemaGuid tables. And I want it works > for any OleDb connection (independently of the DBMS) > > I hope now it is more clear my goal. > > Thank you! > > > > Patrice ha scritto: > > > ...And just loop through the rows using the DataTable.Rows collection > > (it > > would interesting to check if restrictions are applied on the result or > > are > > processed server side for your DB). > > > > Else if you want really a replacement you'll have to use specific > > statements > > for this (for example for SQL Server you could use the > > information_schema.columns view or the appropriate stored procedures). > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > Of course Miha, but I was talking about processing rows (not fields). > > > It's clear that one > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > My question was another: I want a programmatic substitute of > > > GetOleDbSchemaTable > > > that allows me to consider 1 record at a time. > > > > > > Thank you for your reply. > > > > > > -Tom > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > >> You can pass an array of filter values as a last parameter. > > >> > > >> -- > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > >> RightHand .NET consulting & development www.rthand.com > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > >> > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > >> > Hi, > > >> > > > >> > if we have an OleDbConnection it is possible to retrieve a > > >> > datatable > > >> > containing information about the database fields using the > > >> > statement > > >> > (watch out line breaking): > > >> > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > >> > New Object() {}) > > >> > > > >> > This however return a whole DataTable, which in some cases can be > > >> > very > > >> > large. For instance if you do it with SAP you receive over half > > >> > million > > >> > rows. > > >> > > > >> > My question: > > >> > > > >> > I would like to do the same operation programmatically and not > > >> > using > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > > >> > time, > > >> > similarly to the DataReader mechanism. > > >> > > > >> > Can anyone suggest how to achieve that? > > >> > > > >> > -Tom > > >> > > > > Thank you very much all, I will reply to each one:
Patrice, Miha I know well the filtering mechanism but it does not seem to help. Because, for my purposes, I DO have to read ALL the records. What I wished is not to have to store all of them in memory. Just process and dismiss. Your suggestion would turn to be "the" solution if you could be able to provide a filtering mechanism which allows to take N rows at a time n and N and N and N .... and so on Are you able to do that, for any DBMS and without knowing a priori what is stored in the records - (this condition is crucial, because I am working against several kinds of DBMS. For instance SAP can be on SQL server, Oracle, ...) Cor, Yes that one is fine, but it's another piece of information. I am scanning all the schemaguids to get the complete DB structure. -tom Miha Markic [MVP C#] ha scritto: Show quote > Wow, that's big. > Well, I still suggest you to do filtering and process the small amount of > rows. > As another solution, Patrice already mentioned, do execute proper sql > statments to query the database metadata and you will have full control. > Of course, it is database specific then. > > -- > Miha Markic [MVP C#, INETA Country Leader for Slovenia] > RightHand .NET consulting & development www.rthand.com > Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > <tommaso.gasta***@uniroma1.it> wrote in message > news:1152024828.274193.169670@p79g2000cwp.googlegroups.com... > Dear Miha , Patrice, ... and all > > the advantage of having a mechanism similar to DataReader is obvious. > > Assume I am getting only the very first field of the COLUMN schema > table. > > If I connect to SAP and run the GetOleDbSchemaTable command I get a > datatable with 1 field > and over half million rows. > > I would like to get 1 value at a time to process it instead of holding > over half million > values in memory at the same time, which I do not need. > Further I usually need to take and process many more columns at the > same time and the size of the datatable become enormous. > > Of course with small systems this is not a big problem. But try to work > with real world databases... > > -tom > > Patrice ha scritto: > > > English is not may native language either. I should just have been more > > explicit. > > > > This is the second part then. Use a custom replacement for you DBMS with a > > DataReader (note that a DataReader still uses a buffer). > > > > What I wanted to convey with the first part is that the problem lloks like > > to me that that you get all data at once. With restrictions (as suggested > > by > > Miha) you can get only those you are interested using a limited amount of > > memory. Though you may want to check that restrictions are processed > > server > > side it looks like quite a good solution. > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > > Hi Patrice. Thanks... Hmmm, > > it seems I really have problem with my English :) Sorry! > > > > It's clear that - once one has a DataTable - one can read a > > row at a time. > > > > What I was trying to explain is that I do not want to get the > > whole DataTable, but just get one record at a time. > > > > This would be the same difference between: > > > > DataAdapter + Fill() [gets the whole table at a time] > > DataReader + Read() [gets 1 record at a time] > > > > I would like to know how to implement something > > similar to the DataReader + Read() schema > > > > for OleDbSchemaGuid tables. And I want it works > > for any OleDb connection (independently of the DBMS) > > > > I hope now it is more clear my goal. > > > > Thank you! > > > > > > > > Patrice ha scritto: > > > > > ...And just loop through the rows using the DataTable.Rows collection > > > (it > > > would interesting to check if restrictions are applied on the result or > > > are > > > processed server side for your DB). > > > > > > Else if you want really a replacement you'll have to use specific > > > statements > > > for this (for example for SQL Server you could use the > > > information_schema.columns view or the appropriate stored procedures). > > > > > > -- > > > Patrice > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > > Of course Miha, but I was talking about processing rows (not fields). > > > > It's clear that one > > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > > > My question was another: I want a programmatic substitute of > > > > GetOleDbSchemaTable > > > > that allows me to consider 1 record at a time. > > > > > > > > Thank you for your reply. > > > > > > > > -Tom > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > > > >> You can pass an array of filter values as a last parameter. > > > >> > > > >> -- > > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > >> RightHand .NET consulting & development www.rthand.com > > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > >> > > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > > >> > Hi, > > > >> > > > > >> > if we have an OleDbConnection it is possible to retrieve a > > > >> > datatable > > > >> > containing information about the database fields using the > > > >> > statement > > > >> > (watch out line breaking): > > > >> > > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > > >> > New Object() {}) > > > >> > > > > >> > This however return a whole DataTable, which in some cases can be > > > >> > very > > > >> > large. For instance if you do it with SAP you receive over half > > > >> > million > > > >> > rows. > > > >> > > > > >> > My question: > > > >> > > > > >> > I would like to do the same operation programmatically and not > > > >> > using > > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > > > >> > time, > > > >> > similarly to the DataReader mechanism. > > > >> > > > > >> > Can anyone suggest how to achieve that? > > > >> > > > > >> > -Tom > > > >> > > > > > Basically I would do something like :
for each table (using GetOleDbSchemaTable to get all tables) read columns for this table (using GetOleDbSchemaTable with restrictions to get columns only for this table) process these columns next You never have all of them in memory. You just process each table in turn.... -- Show quotePatrice <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: 1152031673.041068.310***@m73g2000cwd.googlegroups.com... Thank you very much all, I will reply to each one: Patrice, Miha I know well the filtering mechanism but it does not seem to help. Because, for my purposes, I DO have to read ALL the records. What I wished is not to have to store all of them in memory. Just process and dismiss. Your suggestion would turn to be "the" solution if you could be able to provide a filtering mechanism which allows to take N rows at a time n and N and N and N .... and so on Are you able to do that, for any DBMS and without knowing a priori what is stored in the records - (this condition is crucial, because I am working against several kinds of DBMS. For instance SAP can be on SQL server, Oracle, ...) Cor, Yes that one is fine, but it's another piece of information. I am scanning all the schemaguids to get the complete DB structure. -tom Miha Markic [MVP C#] ha scritto: > Wow, that's big. > Well, I still suggest you to do filtering and process the small amount of > rows. > As another solution, Patrice already mentioned, do execute proper sql > statments to query the database metadata and you will have full control. > Of course, it is database specific then. > > -- > Miha Markic [MVP C#, INETA Country Leader for Slovenia] > RightHand .NET consulting & development www.rthand.com > Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > <tommaso.gasta***@uniroma1.it> wrote in message > news:1152024828.274193.169670@p79g2000cwp.googlegroups.com... > Dear Miha , Patrice, ... and all > > the advantage of having a mechanism similar to DataReader is obvious. > > Assume I am getting only the very first field of the COLUMN schema > table. > > If I connect to SAP and run the GetOleDbSchemaTable command I get a > datatable with 1 field > and over half million rows. > > I would like to get 1 value at a time to process it instead of holding > over half million > values in memory at the same time, which I do not need. > Further I usually need to take and process many more columns at the > same time and the size of the datatable become enormous. > > Of course with small systems this is not a big problem. But try to work > with real world databases... > > -tom > > Patrice ha scritto: > > > English is not may native language either. I should just have been more > > explicit. > > > > This is the second part then. Use a custom replacement for you DBMS with > > a > > DataReader (note that a DataReader still uses a buffer). > > > > What I wanted to convey with the first part is that the problem lloks > > like > > to me that that you get all data at once. With restrictions (as > > suggested > > by > > Miha) you can get only those you are interested using a limited amount > > of > > memory. Though you may want to check that restrictions are processed > > server > > side it looks like quite a good solution. > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > > Hi Patrice. Thanks... Hmmm, > > it seems I really have problem with my English :) Sorry! > > > > It's clear that - once one has a DataTable - one can read a > > row at a time. > > > > What I was trying to explain is that I do not want to get the > > whole DataTable, but just get one record at a time. > > > > This would be the same difference between: > > > > DataAdapter + Fill() [gets the whole table at a time] > > DataReader + Read() [gets 1 record at a time] > > > > I would like to know how to implement something > > similar to the DataReader + Read() schema > > > > for OleDbSchemaGuid tables. And I want it works > > for any OleDb connection (independently of the DBMS) > > > > I hope now it is more clear my goal. > > > > Thank you! > > > > > > > > Patrice ha scritto: > > > > > ...And just loop through the rows using the DataTable.Rows collection > > > (it > > > would interesting to check if restrictions are applied on the result > > > or > > > are > > > processed server side for your DB). > > > > > > Else if you want really a replacement you'll have to use specific > > > statements > > > for this (for example for SQL Server you could use the > > > information_schema.columns view or the appropriate stored procedures). > > > > > > -- > > > Patrice > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > > Of course Miha, but I was talking about processing rows (not > > > > fields). > > > > It's clear that one > > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > > > My question was another: I want a programmatic substitute of > > > > GetOleDbSchemaTable > > > > that allows me to consider 1 record at a time. > > > > > > > > Thank you for your reply. > > > > > > > > -Tom > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > > > >> You can pass an array of filter values as a last parameter. > > > >> > > > >> -- > > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > >> RightHand .NET consulting & development www.rthand.com > > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > >> > > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > > >> > Hi, > > > >> > > > > >> > if we have an OleDbConnection it is possible to retrieve a > > > >> > datatable > > > >> > containing information about the database fields using the > > > >> > statement > > > >> > (watch out line breaking): > > > >> > > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > > >> > New Object() {}) > > > >> > > > > >> > This however return a whole DataTable, which in some cases can be > > > >> > very > > > >> > large. For instance if you do it with SAP you receive over half > > > >> > million > > > >> > rows. > > > >> > > > > >> > My question: > > > >> > > > > >> > I would like to do the same operation programmatically and not > > > >> > using > > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > > > >> > time, > > > >> > similarly to the DataReader mechanism. > > > >> > > > > >> > Can anyone suggest how to achieve that? > > > >> > > > > >> > -Tom > > > >> > > > > > Yes Patrice,
I never said I am holding all the tables in memory. That would be a suicide :) For now, I am scanning one table at a time. Just wanted to figure ot if i could get a row at a time and dismiss it. But probably it's not something immediate to do, otherwise the answer had probably already popped up. Probably by using some low level function, also used by the GetOledbSchema it would be possible to change it's beaviour from the FILL() way to a kind of READ() way. But I do not have information about that ... We need some OleDb guru .... -tom Patrice ha scritto: Show quote > Basically I would do something like : > > for each table (using GetOleDbSchemaTable to get all tables) > read columns for this table (using GetOleDbSchemaTable with restrictions > to get columns only for this table) > process these columns > next > > You never have all of them in memory. You just process each table in > turn.... > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152031673.041068.310***@m73g2000cwd.googlegroups.com... > Thank you very much all, I will reply to each one: > > Patrice, Miha > > I know well the filtering mechanism but it does not seem > to help. Because, for my purposes, I DO have to read ALL > the records. > > What I wished is not to have to store all of them in memory. > Just process and dismiss. > > Your suggestion would turn to be "the" solution > if you could be able to provide a filtering > mechanism which allows to take N rows at a time > > n and N and N and N .... and so on > > Are you able to do that, for any DBMS and > without knowing a priori what is stored in the records - > (this condition is crucial, because I am working against > several kinds of DBMS. For instance SAP can be on SQL server, > Oracle, ...) > > Cor, > > Yes that one is fine, but it's another piece of information. > I am scanning all the schemaguids to get the complete > DB structure. > > -tom > > > > Miha Markic [MVP C#] ha scritto: > > > Wow, that's big. > > Well, I still suggest you to do filtering and process the small amount of > > rows. > > As another solution, Patrice already mentioned, do execute proper sql > > statments to query the database metadata and you will have full control. > > Of course, it is database specific then. > > > > -- > > Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > RightHand .NET consulting & development www.rthand.com > > Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > <tommaso.gasta***@uniroma1.it> wrote in message > > news:1152024828.274193.169670@p79g2000cwp.googlegroups.com... > > Dear Miha , Patrice, ... and all > > > > the advantage of having a mechanism similar to DataReader is obvious. > > > > Assume I am getting only the very first field of the COLUMN schema > > table. > > > > If I connect to SAP and run the GetOleDbSchemaTable command I get a > > datatable with 1 field > > and over half million rows. > > > > I would like to get 1 value at a time to process it instead of holding > > over half million > > values in memory at the same time, which I do not need. > > Further I usually need to take and process many more columns at the > > same time and the size of the datatable become enormous. > > > > Of course with small systems this is not a big problem. But try to work > > with real world databases... > > > > -tom > > > > Patrice ha scritto: > > > > > English is not may native language either. I should just have been more > > > explicit. > > > > > > This is the second part then. Use a custom replacement for you DBMS with > > > a > > > DataReader (note that a DataReader still uses a buffer). > > > > > > What I wanted to convey with the first part is that the problem lloks > > > like > > > to me that that you get all data at once. With restrictions (as > > > suggested > > > by > > > Miha) you can get only those you are interested using a limited amount > > > of > > > memory. Though you may want to check that restrictions are processed > > > server > > > side it looks like quite a good solution. > > > > > > -- > > > Patrice > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > > > Hi Patrice. Thanks... Hmmm, > > > it seems I really have problem with my English :) Sorry! > > > > > > It's clear that - once one has a DataTable - one can read a > > > row at a time. > > > > > > What I was trying to explain is that I do not want to get the > > > whole DataTable, but just get one record at a time. > > > > > > This would be the same difference between: > > > > > > DataAdapter + Fill() [gets the whole table at a time] > > > DataReader + Read() [gets 1 record at a time] > > > > > > I would like to know how to implement something > > > similar to the DataReader + Read() schema > > > > > > for OleDbSchemaGuid tables. And I want it works > > > for any OleDb connection (independently of the DBMS) > > > > > > I hope now it is more clear my goal. > > > > > > Thank you! > > > > > > > > > > > > Patrice ha scritto: > > > > > > > ...And just loop through the rows using the DataTable.Rows collection > > > > (it > > > > would interesting to check if restrictions are applied on the result > > > > or > > > > are > > > > processed server side for your DB). > > > > > > > > Else if you want really a replacement you'll have to use specific > > > > statements > > > > for this (for example for SQL Server you could use the > > > > information_schema.columns view or the appropriate stored procedures). > > > > > > > > -- > > > > Patrice > > > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > > > Of course Miha, but I was talking about processing rows (not > > > > > fields). > > > > > It's clear that one > > > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > > > > > My question was another: I want a programmatic substitute of > > > > > GetOleDbSchemaTable > > > > > that allows me to consider 1 record at a time. > > > > > > > > > > Thank you for your reply. > > > > > > > > > > -Tom > > > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > > > > > >> You can pass an array of filter values as a last parameter. > > > > >> > > > > >> -- > > > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > > >> RightHand .NET consulting & development www.rthand.com > > > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > >> > > > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > > > >> > Hi, > > > > >> > > > > > >> > if we have an OleDbConnection it is possible to retrieve a > > > > >> > datatable > > > > >> > containing information about the database fields using the > > > > >> > statement > > > > >> > (watch out line breaking): > > > > >> > > > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > > > >> > New Object() {}) > > > > >> > > > > > >> > This however return a whole DataTable, which in some cases can be > > > > >> > very > > > > >> > large. For instance if you do it with SAP you receive over half > > > > >> > million > > > > >> > rows. > > > > >> > > > > > >> > My question: > > > > >> > > > > > >> > I would like to do the same operation programmatically and not > > > > >> > using > > > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at a > > > > >> > time, > > > > >> > similarly to the DataReader mechanism. > > > > >> > > > > > >> > Can anyone suggest how to achieve that? > > > > >> > > > > > >> > -Tom > > > > >> > > > > > > What would be the benefit of having "a row" (even the DataReader uses the
buffer) as opposed to having all rows *for a single table* at any one time in memory. Else use the second approach (using a db specific statements). A third approach would be to use a reflector to see what are the calls that ..NET is doing under the hood and try to reproduce uisng a datareader. IMO it would be best to make sure first you have some kind of real issue here before wasting too much time on "optimizing" this (do you have actually *seen* a problem with scanning one table at a time ?) Good luck... -- Show quotePatrice <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: 1152035037.854510.321***@l70g2000cwa.googlegroups.com... Yes Patrice, I never said I am holding all the tables in memory. That would be a suicide :) For now, I am scanning one table at a time. Just wanted to figure ot if i could get a row at a time and dismiss it. But probably it's not something immediate to do, otherwise the answer had probably already popped up. Probably by using some low level function, also used by the GetOledbSchema it would be possible to change it's beaviour from the FILL() way to a kind of READ() way. But I do not have information about that ... We need some OleDb guru .... -tom Patrice ha scritto: > Basically I would do something like : > > for each table (using GetOleDbSchemaTable to get all tables) > read columns for this table (using GetOleDbSchemaTable with > restrictions > to get columns only for this table) > process these columns > next > > You never have all of them in memory. You just process each table in > turn.... > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152031673.041068.310***@m73g2000cwd.googlegroups.com... > Thank you very much all, I will reply to each one: > > Patrice, Miha > > I know well the filtering mechanism but it does not seem > to help. Because, for my purposes, I DO have to read ALL > the records. > > What I wished is not to have to store all of them in memory. > Just process and dismiss. > > Your suggestion would turn to be "the" solution > if you could be able to provide a filtering > mechanism which allows to take N rows at a time > > n and N and N and N .... and so on > > Are you able to do that, for any DBMS and > without knowing a priori what is stored in the records - > (this condition is crucial, because I am working against > several kinds of DBMS. For instance SAP can be on SQL server, > Oracle, ...) > > Cor, > > Yes that one is fine, but it's another piece of information. > I am scanning all the schemaguids to get the complete > DB structure. > > -tom > > > > Miha Markic [MVP C#] ha scritto: > > > Wow, that's big. > > Well, I still suggest you to do filtering and process the small amount > > of > > rows. > > As another solution, Patrice already mentioned, do execute proper sql > > statments to query the database metadata and you will have full control. > > Of course, it is database specific then. > > > > -- > > Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > RightHand .NET consulting & development www.rthand.com > > Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > <tommaso.gasta***@uniroma1.it> wrote in message > > news:1152024828.274193.169670@p79g2000cwp.googlegroups.com... > > Dear Miha , Patrice, ... and all > > > > the advantage of having a mechanism similar to DataReader is obvious. > > > > Assume I am getting only the very first field of the COLUMN schema > > table. > > > > If I connect to SAP and run the GetOleDbSchemaTable command I get a > > datatable with 1 field > > and over half million rows. > > > > I would like to get 1 value at a time to process it instead of holding > > over half million > > values in memory at the same time, which I do not need. > > Further I usually need to take and process many more columns at the > > same time and the size of the datatable become enormous. > > > > Of course with small systems this is not a big problem. But try to work > > with real world databases... > > > > -tom > > > > Patrice ha scritto: > > > > > English is not may native language either. I should just have been > > > more > > > explicit. > > > > > > This is the second part then. Use a custom replacement for you DBMS > > > with > > > a > > > DataReader (note that a DataReader still uses a buffer). > > > > > > What I wanted to convey with the first part is that the problem lloks > > > like > > > to me that that you get all data at once. With restrictions (as > > > suggested > > > by > > > Miha) you can get only those you are interested using a limited amount > > > of > > > memory. Though you may want to check that restrictions are processed > > > server > > > side it looks like quite a good solution. > > > > > > -- > > > Patrice > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > > > Hi Patrice. Thanks... Hmmm, > > > it seems I really have problem with my English :) Sorry! > > > > > > It's clear that - once one has a DataTable - one can read a > > > row at a time. > > > > > > What I was trying to explain is that I do not want to get the > > > whole DataTable, but just get one record at a time. > > > > > > This would be the same difference between: > > > > > > DataAdapter + Fill() [gets the whole table at a time] > > > DataReader + Read() [gets 1 record at a time] > > > > > > I would like to know how to implement something > > > similar to the DataReader + Read() schema > > > > > > for OleDbSchemaGuid tables. And I want it works > > > for any OleDb connection (independently of the DBMS) > > > > > > I hope now it is more clear my goal. > > > > > > Thank you! > > > > > > > > > > > > Patrice ha scritto: > > > > > > > ...And just loop through the rows using the DataTable.Rows > > > > collection > > > > (it > > > > would interesting to check if restrictions are applied on the result > > > > or > > > > are > > > > processed server side for your DB). > > > > > > > > Else if you want really a replacement you'll have to use specific > > > > statements > > > > for this (for example for SQL Server you could use the > > > > information_schema.columns view or the appropriate stored > > > > procedures). > > > > > > > > -- > > > > Patrice > > > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > > > Of course Miha, but I was talking about processing rows (not > > > > > fields). > > > > > It's clear that one > > > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > > > > > My question was another: I want a programmatic substitute of > > > > > GetOleDbSchemaTable > > > > > that allows me to consider 1 record at a time. > > > > > > > > > > Thank you for your reply. > > > > > > > > > > -Tom > > > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > > > > > >> You can pass an array of filter values as a last parameter. > > > > >> > > > > >> -- > > > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > > >> RightHand .NET consulting & development www.rthand.com > > > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > >> > > > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > > > >> > Hi, > > > > >> > > > > > >> > if we have an OleDbConnection it is possible to retrieve a > > > > >> > datatable > > > > >> > containing information about the database fields using the > > > > >> > statement > > > > >> > (watch out line breaking): > > > > >> > > > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > > > >> > New Object() {}) > > > > >> > > > > > >> > This however return a whole DataTable, which in some cases can > > > > >> > be > > > > >> > very > > > > >> > large. For instance if you do it with SAP you receive over half > > > > >> > million > > > > >> > rows. > > > > >> > > > > > >> > My question: > > > > >> > > > > > >> > I would like to do the same operation programmatically and not > > > > >> > using > > > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at > > > > >> > a > > > > >> > time, > > > > >> > similarly to the DataReader mechanism. > > > > >> > > > > > >> > Can anyone suggest how to achieve that? > > > > >> > > > > > >> > -Tom > > > > >> > > > > > > Thank you Patrice,
hmmm... I find quite interesting the part where you talk about a "reflector". Actually I have often seen people on this group who were able to provide details of the inner working of some procedures and I have been wondering where they get that information. Sounds like a kind of tool to see the inner working of the language commands. Do you have any pointer about that? Is there a tool that can be downloaded? Thanks, tom Patrice ha scritto: Show quote > What would be the benefit of having "a row" (even the DataReader uses the > buffer) as opposed to having all rows *for a single table* at any one time > in memory. > > Else use the second approach (using a db specific statements). > > A third approach would be to use a reflector to see what are the calls that > .NET is doing under the hood and try to reproduce uisng a datareader. > > IMO it would be best to make sure first you have some kind of real issue > here before wasting too much time on "optimizing" this (do you have actually > *seen* a problem with scanning one table at a time ?) > > Good luck... > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152035037.854510.321***@l70g2000cwa.googlegroups.com... > Yes Patrice, > > I never said I am holding all the tables in memory. That would > be a suicide :) For now, I am scanning one table at a time. > > Just wanted to figure ot if i could get a row at a time and dismiss it. > But > probably it's not something immediate to do, otherwise the answer had > probably already popped up. > > Probably by using some low level function, also used by the > GetOledbSchema > it would be possible to change it's beaviour from the FILL() way to a > kind of READ() way. > > But I do not have information about that ... We need some OleDb guru > ... > > -tom > > Patrice ha scritto: > > > Basically I would do something like : > > > > for each table (using GetOleDbSchemaTable to get all tables) > > read columns for this table (using GetOleDbSchemaTable with > > restrictions > > to get columns only for this table) > > process these columns > > next > > > > You never have all of them in memory. You just process each table in > > turn.... > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152031673.041068.310***@m73g2000cwd.googlegroups.com... > > Thank you very much all, I will reply to each one: > > > > Patrice, Miha > > > > I know well the filtering mechanism but it does not seem > > to help. Because, for my purposes, I DO have to read ALL > > the records. > > > > What I wished is not to have to store all of them in memory. > > Just process and dismiss. > > > > Your suggestion would turn to be "the" solution > > if you could be able to provide a filtering > > mechanism which allows to take N rows at a time > > > > n and N and N and N .... and so on > > > > Are you able to do that, for any DBMS and > > without knowing a priori what is stored in the records - > > (this condition is crucial, because I am working against > > several kinds of DBMS. For instance SAP can be on SQL server, > > Oracle, ...) > > > > Cor, > > > > Yes that one is fine, but it's another piece of information. > > I am scanning all the schemaguids to get the complete > > DB structure. > > > > -tom > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > Wow, that's big. > > > Well, I still suggest you to do filtering and process the small amount > > > of > > > rows. > > > As another solution, Patrice already mentioned, do execute proper sql > > > statments to query the database metadata and you will have full control. > > > Of course, it is database specific then. > > > > > > -- > > > Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > RightHand .NET consulting & development www.rthand.com > > > Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > > > <tommaso.gasta***@uniroma1.it> wrote in message > > > news:1152024828.274193.169670@p79g2000cwp.googlegroups.com... > > > Dear Miha , Patrice, ... and all > > > > > > the advantage of having a mechanism similar to DataReader is obvious. > > > > > > Assume I am getting only the very first field of the COLUMN schema > > > table. > > > > > > If I connect to SAP and run the GetOleDbSchemaTable command I get a > > > datatable with 1 field > > > and over half million rows. > > > > > > I would like to get 1 value at a time to process it instead of holding > > > over half million > > > values in memory at the same time, which I do not need. > > > Further I usually need to take and process many more columns at the > > > same time and the size of the datatable become enormous. > > > > > > Of course with small systems this is not a big problem. But try to work > > > with real world databases... > > > > > > -tom > > > > > > Patrice ha scritto: > > > > > > > English is not may native language either. I should just have been > > > > more > > > > explicit. > > > > > > > > This is the second part then. Use a custom replacement for you DBMS > > > > with > > > > a > > > > DataReader (note that a DataReader still uses a buffer). > > > > > > > > What I wanted to convey with the first part is that the problem lloks > > > > like > > > > to me that that you get all data at once. With restrictions (as > > > > suggested > > > > by > > > > Miha) you can get only those you are interested using a limited amount > > > > of > > > > memory. Though you may want to check that restrictions are processed > > > > server > > > > side it looks like quite a good solution. > > > > > > > > -- > > > > Patrice > > > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > > > > Hi Patrice. Thanks... Hmmm, > > > > it seems I really have problem with my English :) Sorry! > > > > > > > > It's clear that - once one has a DataTable - one can read a > > > > row at a time. > > > > > > > > What I was trying to explain is that I do not want to get the > > > > whole DataTable, but just get one record at a time. > > > > > > > > This would be the same difference between: > > > > > > > > DataAdapter + Fill() [gets the whole table at a time] > > > > DataReader + Read() [gets 1 record at a time] > > > > > > > > I would like to know how to implement something > > > > similar to the DataReader + Read() schema > > > > > > > > for OleDbSchemaGuid tables. And I want it works > > > > for any OleDb connection (independently of the DBMS) > > > > > > > > I hope now it is more clear my goal. > > > > > > > > Thank you! > > > > > > > > > > > > > > > > Patrice ha scritto: > > > > > > > > > ...And just loop through the rows using the DataTable.Rows > > > > > collection > > > > > (it > > > > > would interesting to check if restrictions are applied on the result > > > > > or > > > > > are > > > > > processed server side for your DB). > > > > > > > > > > Else if you want really a replacement you'll have to use specific > > > > > statements > > > > > for this (for example for SQL Server you could use the > > > > > information_schema.columns view or the appropriate stored > > > > > procedures). > > > > > > > > > > -- > > > > > Patrice > > > > > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > > > > Of course Miha, but I was talking about processing rows (not > > > > > > fields). > > > > > > It's clear that one > > > > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > > > > > > > My question was another: I want a programmatic substitute of > > > > > > GetOleDbSchemaTable > > > > > > that allows me to consider 1 record at a time. > > > > > > > > > > > > Thank you for your reply. > > > > > > > > > > > > -Tom > > > > > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > > > > > > > >> You can pass an array of filter values as a last parameter. > > > > > >> > > > > > >> -- > > > > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > > > >> RightHand .NET consulting & development www.rthand.com > > > > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > > >> > > > > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > > > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > > > > >> > Hi, > > > > > >> > > > > > > >> > if we have an OleDbConnection it is possible to retrieve a > > > > > >> > datatable > > > > > >> > containing information about the database fields using the > > > > > >> > statement > > > > > >> > (watch out line breaking): > > > > > >> > > > > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > > > > >> > New Object() {}) > > > > > >> > > > > > > >> > This however return a whole DataTable, which in some cases can > > > > > >> > be > > > > > >> > very > > > > > >> > large. For instance if you do it with SAP you receive over half > > > > > >> > million > > > > > >> > rows. > > > > > >> > > > > > > >> > My question: > > > > > >> > > > > > > >> > I would like to do the same operation programmatically and not > > > > > >> > using > > > > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record at > > > > > >> > a > > > > > >> > time, > > > > > >> > similarly to the DataReader mechanism. > > > > > >> > > > > > > >> > Can anyone suggest how to achieve that? > > > > > >> > > > > > > >> > -Tom > > > > > >> > > > > > > > Reflector
http://www.aisto.com/roeder/dotnet/ It has not to do with reflection Cor <tommaso.gasta***@uniroma1.it> schreef in bericht news:1152037385.651259.145280@j8g2000cwa.googlegroups.com... Thank you Patrice,hmmm... I find quite interesting the part where you talk about a "reflector". Actually I have often seen people on this group who were able to provide details of the inner working of some procedures and I have been wondering where they get that information. Sounds like a kind of tool to see the inner working of the language commands. Do you have any pointer about that? Is there a tool that can be downloaded? Thanks, tom Patrice ha scritto: Show quote > What would be the benefit of having "a row" (even the DataReader uses the > buffer) as opposed to having all rows *for a single table* at any one time > in memory. > > Else use the second approach (using a db specific statements). > > A third approach would be to use a reflector to see what are the calls > that > .NET is doing under the hood and try to reproduce uisng a datareader. > > IMO it would be best to make sure first you have some kind of real issue > here before wasting too much time on "optimizing" this (do you have > actually > *seen* a problem with scanning one table at a time ?) > > Good luck... > > -- > Patrice > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > 1152035037.854510.321***@l70g2000cwa.googlegroups.com... > Yes Patrice, > > I never said I am holding all the tables in memory. That would > be a suicide :) For now, I am scanning one table at a time. > > Just wanted to figure ot if i could get a row at a time and dismiss it. > But > probably it's not something immediate to do, otherwise the answer had > probably already popped up. > > Probably by using some low level function, also used by the > GetOledbSchema > it would be possible to change it's beaviour from the FILL() way to a > kind of READ() way. > > But I do not have information about that ... We need some OleDb guru > ... > > -tom > > Patrice ha scritto: > > > Basically I would do something like : > > > > for each table (using GetOleDbSchemaTable to get all tables) > > read columns for this table (using GetOleDbSchemaTable with > > restrictions > > to get columns only for this table) > > process these columns > > next > > > > You never have all of them in memory. You just process each table in > > turn.... > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152031673.041068.310***@m73g2000cwd.googlegroups.com... > > Thank you very much all, I will reply to each one: > > > > Patrice, Miha > > > > I know well the filtering mechanism but it does not seem > > to help. Because, for my purposes, I DO have to read ALL > > the records. > > > > What I wished is not to have to store all of them in memory. > > Just process and dismiss. > > > > Your suggestion would turn to be "the" solution > > if you could be able to provide a filtering > > mechanism which allows to take N rows at a time > > > > n and N and N and N .... and so on > > > > Are you able to do that, for any DBMS and > > without knowing a priori what is stored in the records - > > (this condition is crucial, because I am working against > > several kinds of DBMS. For instance SAP can be on SQL server, > > Oracle, ...) > > > > Cor, > > > > Yes that one is fine, but it's another piece of information. > > I am scanning all the schemaguids to get the complete > > DB structure. > > > > -tom > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > Wow, that's big. > > > Well, I still suggest you to do filtering and process the small amount > > > of > > > rows. > > > As another solution, Patrice already mentioned, do execute proper sql > > > statments to query the database metadata and you will have full > > > control. > > > Of course, it is database specific then. > > > > > > -- > > > Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > RightHand .NET consulting & development www.rthand.com > > > Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > > > <tommaso.gasta***@uniroma1.it> wrote in message > > > news:1152024828.274193.169670@p79g2000cwp.googlegroups.com... > > > Dear Miha , Patrice, ... and all > > > > > > the advantage of having a mechanism similar to DataReader is obvious. > > > > > > Assume I am getting only the very first field of the COLUMN schema > > > table. > > > > > > If I connect to SAP and run the GetOleDbSchemaTable command I get a > > > datatable with 1 field > > > and over half million rows. > > > > > > I would like to get 1 value at a time to process it instead of holding > > > over half million > > > values in memory at the same time, which I do not need. > > > Further I usually need to take and process many more columns at the > > > same time and the size of the datatable become enormous. > > > > > > Of course with small systems this is not a big problem. But try to > > > work > > > with real world databases... > > > > > > -tom > > > > > > Patrice ha scritto: > > > > > > > English is not may native language either. I should just have been > > > > more > > > > explicit. > > > > > > > > This is the second part then. Use a custom replacement for you DBMS > > > > with > > > > a > > > > DataReader (note that a DataReader still uses a buffer). > > > > > > > > What I wanted to convey with the first part is that the problem > > > > lloks > > > > like > > > > to me that that you get all data at once. With restrictions (as > > > > suggested > > > > by > > > > Miha) you can get only those you are interested using a limited > > > > amount > > > > of > > > > memory. Though you may want to check that restrictions are processed > > > > server > > > > side it looks like quite a good solution. > > > > > > > > -- > > > > Patrice > > > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > > 1152019369.810484.36***@m79g2000cwm.googlegroups.com... > > > > Hi Patrice. Thanks... Hmmm, > > > > it seems I really have problem with my English :) Sorry! > > > > > > > > It's clear that - once one has a DataTable - one can read a > > > > row at a time. > > > > > > > > What I was trying to explain is that I do not want to get the > > > > whole DataTable, but just get one record at a time. > > > > > > > > This would be the same difference between: > > > > > > > > DataAdapter + Fill() [gets the whole table at a time] > > > > DataReader + Read() [gets 1 record at a time] > > > > > > > > I would like to know how to implement something > > > > similar to the DataReader + Read() schema > > > > > > > > for OleDbSchemaGuid tables. And I want it works > > > > for any OleDb connection (independently of the DBMS) > > > > > > > > I hope now it is more clear my goal. > > > > > > > > Thank you! > > > > > > > > > > > > > > > > Patrice ha scritto: > > > > > > > > > ...And just loop through the rows using the DataTable.Rows > > > > > collection > > > > > (it > > > > > would interesting to check if restrictions are applied on the > > > > > result > > > > > or > > > > > are > > > > > processed server side for your DB). > > > > > > > > > > Else if you want really a replacement you'll have to use specific > > > > > statements > > > > > for this (for example for SQL Server you could use the > > > > > information_schema.columns view or the appropriate stored > > > > > procedures). > > > > > > > > > > -- > > > > > Patrice > > > > > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > > > 1152014788.799707.303***@p79g2000cwp.googlegroups.com... > > > > > > Of course Miha, but I was talking about processing rows (not > > > > > > fields). > > > > > > It's clear that one > > > > > > can select columns passing an argument to GetOleDbSchemaTable. > > > > > > > > > > > > My question was another: I want a programmatic substitute of > > > > > > GetOleDbSchemaTable > > > > > > that allows me to consider 1 record at a time. > > > > > > > > > > > > Thank you for your reply. > > > > > > > > > > > > -Tom > > > > > > > > > > > > Miha Markic [MVP C#] ha scritto: > > > > > > > > > > > >> You can pass an array of filter values as a last parameter. > > > > > >> > > > > > >> -- > > > > > >> Miha Markic [MVP C#, INETA Country Leader for Slovenia] > > > > > >> RightHand .NET consulting & development www.rthand.com > > > > > >> Blog: http://cs.rthand.com/blogs/blog_with_righthand/ > > > > > >> > > > > > >> <tommaso.gasta***@uniroma1.it> wrote in message > > > > > >> news:1152010501.294188.288110@m79g2000cwm.googlegroups.com... > > > > > >> > Hi, > > > > > >> > > > > > > >> > if we have an OleDbConnection it is possible to retrieve a > > > > > >> > datatable > > > > > >> > containing information about the database fields using the > > > > > >> > statement > > > > > >> > (watch out line breaking): > > > > > >> > > > > > > >> > OleDbConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Columns, > > > > > >> > New Object() {}) > > > > > >> > > > > > > >> > This however return a whole DataTable, which in some cases > > > > > >> > can > > > > > >> > be > > > > > >> > very > > > > > >> > large. For instance if you do it with SAP you receive over > > > > > >> > half > > > > > >> > million > > > > > >> > rows. > > > > > >> > > > > > > >> > My question: > > > > > >> > > > > > > >> > I would like to do the same operation programmatically and > > > > > >> > not > > > > > >> > using > > > > > >> > the statement GetOleDbSchemaTable. Possibly taking 1 record > > > > > >> > at > > > > > >> > a > > > > > >> > time, > > > > > >> > similarly to the DataReader mechanism. > > > > > >> > > > > > > >> > Can anyone suggest how to achieve that? > > > > > >> > > > > > > >> > -Tom > > > > > >> > > > > > > > Thank you Cor!! Just got it. This opens up a whole new world! '..................... Public Function GetOleDbSchemaTable(ByVal schema As Guid, ByVal restrictions As Object()) As DataTable Dim table1 As DataTable Dim ptr1 As IntPtr OleDbConnection.ExecutePermission.Demand Bid.ScopeEnter(ptr1, "<oledb.OleDbConnection.GetOleDbSchemaTable|API> %d#, schema=%p{GUID}, restrictions" & ChrW(10), Me.ObjectID, schema) Try Me.CheckStateOpen("GetOleDbSchemaTable") Dim internal1 As OleDbConnectionInternal = Me.GetOpenConnection If (OleDbSchemaGuid.DbInfoLiterals = schema) Then If ((Not restrictions Is Nothing) AndAlso (restrictions.Length <> 0)) Then Throw ODB.InvalidRestrictionsDbInfoLiteral("restrictions") End If Return internal1.BuildInfoLiterals End If If (OleDbSchemaGuid.SchemaGuids = schema) Then If ((Not restrictions Is Nothing) AndAlso (restrictions.Length <> 0)) Then Throw ODB.InvalidRestrictionsSchemaGuids("restrictions") End If Return internal1.BuildSchemaGuids End If If (OleDbSchemaGuid.DbInfoKeywords = schema) Then If ((Not restrictions Is Nothing) AndAlso (restrictions.Length <> 0)) Then Throw ODB.InvalidRestrictionsDbInfoKeywords("restrictions") End If Return internal1.BuildInfoKeywords End If If Not internal1.SupportSchemaRowset(schema) Then Dim wrapper1 As IDBSchemaRowsetWrapper = internal1.IDBSchemaRowset Try If (wrapper1.Value Is Nothing) Then Throw ODB.SchemaRowsetsNotSupported(Me.Provider) End If Finally wrapper1.Dispose End Try Throw ODB.NotSupportedSchemaTable(schema, Me) End If Return internal1.GetSchemaRowset(schema, restrictions) Finally Bid.ScopeLeave(ptr1) End Try Return table1 End Function '..................... I am just wondering. Is this all legal?? On one thing I do not agree with you: I think this has all to do with reflection! :) Thanks a lot, -tom Cor Ligthert [MVP] ha scritto: Show quote > Reflector > > http://www.aisto.com/roeder/dotnet/ > > It has not to do with reflection > > Cor > > > <tommaso.gasta***@uniroma1.it> schreef in bericht > news:1152037385.651259.145280@j8g2000cwa.googlegroups.com... > Thank you Patrice, > > hmmm... > > I find quite interesting the part where you talk about a "reflector". > Actually > I have often seen people on this group who were able to provide details > of the inner working of some procedures and I have been wondering where > they get that information. Sounds like a kind of tool to see the inner > working > of the language commands. > > Do you have any pointer about that? Is there a tool that can be > downloaded? > > Thanks, > > tom > > Patrice ha scritto: > > > What would be the benefit of having "a row" (even the DataReader uses the > > buffer) as opposed to having all rows *for a single table* at any one time > > in memory. > > > > Else use the second approach (using a db specific statements). > > > > A third approach would be to use a reflector to see what are the calls > > that > > .NET is doing under the hood and try to reproduce uisng a datareader. > > > > IMO it would be best to make sure first you have some kind of real issue > > here before wasting too much time on "optimizing" this (do you have > > actually > > *seen* a problem with scanning one table at a time ?) > > > > Good luck... > > > > -- > > Patrice > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > 1152035037.854510.321***@l70g2000cwa.googlegroups.com... > > Yes Patrice, > > > > I never said I am holding all the tables in memory. That would > > be a suicide :) For now, I am scanning one table at a time. > > > > Just wanted to figure ot if i could get a row at a time and dismiss it. > > But > > probably it's not something immediate to do, otherwise the answer had > > probably already popped up. > > > > Probably by using some low level function, also used by the > > GetOledbSchema > > it would be possible to change it's beaviour from the FILL() way to a > > kind of READ() way. > > > > But I do not have information about that ... We need some OleDb guru > > ... > > > > -tom > > > > Patrice ha scritto: > > > > > Basically I would do something like : > > > > > > for each table (using GetOleDbSchemaTable to get all tables) > > > read columns for this table (using GetOleDbSchemaTable with > > > restrictions > > > to get columns only for this table) > > > process these columns > > > next > > > > > > You never have all of them in memory. You just process each table in > > > turn.... > > > > > > -- > > > Patrice > > > > > > <tommaso.gasta***@uniroma1.it> a écrit dans le message de news: > > > 1152031673.041068.310***@m73g2000cwd.googlegroups.com... > > > Thank you very much all, I will reply to each one: > > > > > > Patrice, Miha > > > > > > I know well the filtering mechanism but it does not seem > > > to help. Because, for my purposes, I DO have to read ALL > > > the records. > > > > > > What I wished is not to have to store all of them in memory. > > > Just process and dismiss. > > > > > > Your suggestion would turn to be "the" solution > > > if you could be able to provide a filtering > > > mechanism which allo | |||||||||||||||||||||||
