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Message Posted: Wed, 05 Mar 2008 @ 09:28:24 GMT
I have a quite strange issue with the Teradata ODBC Driver. Acutally it might be no problem just need to understand.
We have a SQL which is generated via Cognos 8 and has a lot of Table joins, Unions etc.
In total the SQL has a size of 178 KB (in a textfile).
When we run this SQL against Teradata it takes about 30 Seconds before even something happen (we watched PMON to see whats going on on the Database).
And there is no difference if we run the SQL via Cognos or on SQL assistant. Even a simple explain takes about 30 Second on Sql Assistant. But wen we run the same SQL on BTEQ we can see that the Database will get busy imediately.
We used Teradata ODBC 3.05.x and also the latest for V12. No difference at all.
So I would like to understand the reason. I mean I was running several other explains which took up to 10 Seconds but they haven't been that huge. The explanation I have (more my assumption) is that the ODBC Driver is parsing the SQL before it will be send out to the Database. We tried to uncheck this section in the ODBC Driver but we got then an Error.
I was recreating the Tablestruction in my Demo environmet with empty tables and the Performance was exactly the same. The processor Workload went high but nothing happend on the Database.
So there is no difference if the Tables are empty or they have millions of rows.
Is it because TD tries to get all needed information, e.g. Statistics, Tablessize etc. to decide which execution path would be the best (but I doubt that this takes 30 Seconds)?
Is it due the Parsing Engine since the SQL is that big?
Does someone have any idea or recommendation?
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