On Fri, 5 Nov 2021 22:16:48 -0400 Michael Potter <pottmi@xxxxxxxxx> wrote: > Is there any good documentation for esql usage with GnuCOBOL? There is no good documentation, no. There is almost no documentation. I have yet to see any documentation for any esql project that describes how to set ODBC options, or control transactions, for example. > Any tips for us as we get started? https://gitlab.cobolworx.com/gnucobol/sql I proved to myself that contrib/esql can connect to a variety of DBMSs via ODBC. You might already have gone further than that yourself. I did not attempt any performance measurements. In my experience ODBC is as efficient as any other client library for database applications. But that is not to say that all database-access libraries are equal, or for that matter, perfected. If you encounter difficulties and want to diagnose them, I can help you isolate the source of any delay. Database applications are fundamentatlly I/O bound (or should be) and performance problems are almost always due to (sometimes intractable) design errors either in the application or in the database itself. Simon's Postgres experience raised some questions about how contrib/esql uses ODBC to support its API. There might be some opportunity to wring better performance from it under certain access patterns. For example, applications that were originally designed for ISAM and later adapted to SQL have a tendency to perform client-side JOINs: do A: read one row from master table do B: read one row from detail table repeat B repeat A That kind of thing yields notoriously bad performance because it prevents the DBMS from exploiting its features. Any filtering happens on the client, and the DBMS's caches and indices are mostly wasted. --jkl
