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Commit916afca

Amit Kapila

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Fix the overrun in hash index metapage for smaller block sizes.

The commit620b49a changed the value of HASH_MAX_BITMAPS with the intentto allow many non-unique values in hash indexes without worrying to reachthe limit of the number of overflow pages. At that time, this didn'toccur to us that it can overrun the block for smaller block sizes.Choose the value of HASH_MAX_BITMAPS based on BLCKSZ such that it givesthe same answer as now for the cases where the overrun doesn't occur, andsome other sufficiently-value for the cases where an overrun currentlydoes occur. This allows us not to change the behavior in any case thatcurrently works, so there's really no reason for a HASH_VERSION bump.Author: Dilip KumarReviewed-by: Amit KapilaBackpatch-through: 10Discussion:https://postgr.es/m/CAA4eK1LtF4VmU4mx_+i72ff1MdNZ8XaJMGkt2HV8+uSWcn8t4A@mail.gmail.com

1 parent0f3637a commit916afcaCopy full SHA for 916afca

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src/include/access
- hash.h

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`‎src/include/access/hash.h`

Lines changed: 5 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -182,9 +182,12 @@ typedef HashScanOpaqueData *HashScanOpaque;`
`182`	`182`	`*`
`183`	`183`	`* There is no particular upper limit on the size of mapp[], other than`
`184`	`184`	`* needing to fit into the metapage. (With 8K block size, 1024 bitmaps`
`185`		`- * limit us to 256 GB of overflow space...)`
	`185`	`+ * limit us to 256 GB of overflow space...). For smaller block size we`
	`186`	`+ * can not use 1024 bitmaps as it will lead to the meta page data crossing`
	`187`	`+ * the block size boundary. So we use BLCKSZ to determine the maximum number`
	`188`	`+ * of bitmaps.`
`186`	`189`	`*/`
`187`		`-#defineHASH_MAX_BITMAPS1024`
	`190`	`+#defineHASH_MAX_BITMAPSMin(BLCKSZ / 8,1024)`
`188`	`191`
`189`	`192`	`#defineHASH_SPLITPOINT_PHASE_BITS2`
`190`	`193`	`#defineHASH_SPLITPOINT_PHASES_PER_GRP(1 << HASH_SPLITPOINT_PHASE_BITS)`

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Commit916afca

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`‎src/include/access/hash.h`

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