| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alban Hertroys <alban(at)magproductions(dot)nl> |
| Cc: | pgsql-general(at)postgreSQL(dot)org, pgsql-hackers(at)postgreSQL(dot)org |
| Subject: | Re: Queries joining views |
| Date: | 2006-08-23 12:50:32 |
| Message-ID: | 18053.1156337432@sss.pgh.pa.us |
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| Lists: | pgsql-general pgsql-hackers |
Alban Hertroys <alban(at)magproductions(dot)nl> writes:
> Mm_object is always larger than any other table in the database, as
> every table joins with (different) records in it to determine it's otype
> and owner. So I don't understand how a fraction of any of those tables
> could be larger than mm_object as a whole...
No, I said a larger fraction, not a larger absolute number of tuples.
The problem is that because mm_product contains only very small values
of "number", a mergejoin looks like a great way to join it to mm_object:
only the first 5% of mm_object will need to be scanned. The bug
consists in applying that 5% number to mm_insrel, for which it's not
correct.
regards, tom lane
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