Re: [HACKERS] Slow count(*) again...

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On PostgreSQL, the difference in no hints and hints for that one query with skewed data is that the query finishes a little faster. On some others, which shall remain nameless, it is the difference between finishing in seconds or days, or maybe never. Hints can be useful, but I can also see why they are not a top priority. They are rarely needed, and only when working around a bug. If you want them so badly, you have the source, write a contrib module (can you do that on Oracle or MSSQL?) If I have a choice between the developers spending time on implementing hints, and spending time on improving the optimiser, I'll take the optimiser.

Tom Kyte agrees:
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:8912905298920
http://tkyte.blogspot.com/2006/08/words-of-wisdom.html



Oracle can be faster on count queries, but that is the only case I have seen. Generally on most other queries, especially when it involves complex joins, or indexes on text fields, PostgreSQL is faster on the same hardware.


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