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Commitfd734f3

jeff-davis

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Use pg_bitutils for HyperLogLog.

Using pg_leftmost_one_post32() yields substantial performance benefits.Backpatching to version 13 because HLL is used for HashAggimprovements in9878b64, which was also backpatched to 13.Reviewed-by: Peter GeogheganDiscussion:https://postgr.es/m/CAH2-WzkGvDKVDo+0YvfvZ+1CE=iCi88DCOGFF3i1hTGGaxcKPw@mail.gmail.comBackpatch-through: 13

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src/backend/lib
- hyperloglog.c

1 file changed

+8

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`‎src/backend/lib/hyperloglog.c`

Lines changed: 8 additions & 5 deletions

Original file line number	Diff line number	Diff line change
`@@ -49,6 +49,7 @@`
`49`	`49`	`#include<math.h>`
`50`	`50`
`51`	`51`	`#include"lib/hyperloglog.h"`
	`52`	`+#include"port/pg_bitutils.h"`
`52`	`53`
`53`	`54`	`#definePOW_2_32(4294967296.0)`
`54`	`55`	`#defineNEG_POW_2_32(-4294967296.0)`
`@@ -242,11 +243,13 @@ rho(uint32 x, uint8 b)`
`242`	`243`	`{`
`243`	`244`	`uint8j=1;`
`244`	`245`
`245`		`-while (j <=b&& !(x&0x80000000))`
`246`		`-{`
`247`		`-j++;`
`248`		`-x <<=1;`
`249`		`-}`
	`246`	`+if (x==0)`
	`247`	`+returnb+1;`
	`248`	`+`
	`249`	`+j=32-pg_leftmost_one_pos32(x);`
	`250`	`+`
	`251`	`+if (j>b)`
	`252`	`+returnb+1;`
`250`	`253`
`251`	`254`	`returnj;`
`252`	`255`	`}`

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