Tom Lane <t...@sss.pgh.pa.us> wrote: > Yeah, TOAST indexes are 2-column. It would be best to exclude > those from your counts, since it seems pretty unlikely that anyone > will care how fast nodeIndexonlyscan.c is for scans on toast > tables. User indexes (excluding toast): indnatts | count ----------+------- 1 | 200 2 | 222 3 | 155 4 | 76 5 | 43 6 | 13 7 | 2 9 | 1 (8 rows) System indexes (excluding toast): indnatts | count ----------+------- 1 | 46 2 | 24 3 | 9 4 | 5 (4 rows) > It doesn't look to me like the mean is above 2 (unless you have > many fewer toast tables than I suspect), so trying to optimize > many-column cases isn't going to help. The mean is 2.4 (give or take a little depending on whether you include system tables). I have no idea where the optimization becomes worthwhile, but the assertion that most indexes probably have a single column worried me. I'm sure there are databases where that is true (especially for those who insist on adding a meaningless surrogate key column to every table), but there are many where it isn't true. I would guess that our average of 2.4 is higher than most, though. -Kevin
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