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Revert ill-considered change of index-size fudge factor.

This partially reverts commit21a39de,restoring the pre-9.2 cost estimates for index usage. That changeintroduced much too large a bias against larger indexes, as per reportsfrom Jeff Janes and others. The whole thing needs a rewrite, which I'vedone in HEAD, but the safest thing to do in 9.2 is just to undo thismultiplier change.

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src/backend/utils/adt
- selfuncs.c

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`‎src/backend/utils/adt/selfuncs.c`

Lines changed: 2 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -6130,11 +6130,11 @@ genericcostestimate(PlannerInfo *root,`
`6130`	`6130`	`*`
`6131`	`6131`	`* We can deal with this by adding a very small "fudge factor" that`
`6132`	`6132`	`* depends on the index size. The fudge factor used here is one`
`6133`		`- * spc_random_page_cost per10000 index pages, which should be small`
	`6133`	`+ * spc_random_page_cost per100000 index pages, which should be small`
`6134`	`6134`	`* enough to not alter index-vs-seqscan decisions, but will prevent`
`6135`	`6135`	`* indexes of different sizes from looking exactly equally attractive.`
`6136`	`6136`	`*/`
`6137`		`-indexTotalCost+=index->pagesspc_random_page_cost /10000.0;`
	`6137`	`+indexTotalCost+=index->pagesspc_random_page_cost /100000.0;`
`6138`	`6138`
`6139`	`6139`	`/*`
`6140`	`6140`	`* CPU cost: any complex expressions in the indexquals will need to be`

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Commit3e9960e

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`‎src/backend/utils/adt/selfuncs.c`

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