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Speed up hex_encode with bytewise lookup

Previously, hex_encode looked up each nibble of the inputseparately. We now use a larger lookup table containing the two-byteencoding of every possible input byte, resulting in a 1/3 reductionin encoding time.Reviewed by Tom Lane, Michael Paquier, Nathan Bossart, David RowleyDiscussion:https://postgr.es/m/CANWCAZZvXuJMgqMN4u068Yqa19CEjS31tQKZp_qFFFbgYfaXqQ%40mail.gmail.com

1 parent0869ea4 commite24d770Copy full SHA for e24d770

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src/backend/utils/adt
- encode.c

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+24

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`‎src/backend/utils/adt/encode.c`

Lines changed: 24 additions & 3 deletions

Original file line number	Diff line number	Diff line change
`@@ -145,7 +145,26 @@ binary_decode(PG_FUNCTION_ARGS)`
`145`	`145`	`* HEX`
`146`	`146`	`*/`
`147`	`147`
`148`		`-staticconstcharhextbl[]="0123456789abcdef";`
	`148`	`+/*`
	`149`	`+ * The hex expansion of each possible byte value (two chars per value).`
	`150`	`+ */`
	`151`	`+staticconstcharhextbl[512]=`
	`152`	`+"000102030405060708090a0b0c0d0e0f"`
	`153`	`+"101112131415161718191a1b1c1d1e1f"`
	`154`	`+"202122232425262728292a2b2c2d2e2f"`
	`155`	`+"303132333435363738393a3b3c3d3e3f"`
	`156`	`+"404142434445464748494a4b4c4d4e4f"`
	`157`	`+"505152535455565758595a5b5c5d5e5f"`
	`158`	`+"606162636465666768696a6b6c6d6e6f"`
	`159`	`+"707172737475767778797a7b7c7d7e7f"`
	`160`	`+"808182838485868788898a8b8c8d8e8f"`
	`161`	`+"909192939495969798999a9b9c9d9e9f"`
	`162`	`+"a0a1a2a3a4a5a6a7a8a9aaabacadaeaf"`
	`163`	`+"b0b1b2b3b4b5b6b7b8b9babbbcbdbebf"`
	`164`	`+"c0c1c2c3c4c5c6c7c8c9cacbcccdcecf"`
	`165`	`+"d0d1d2d3d4d5d6d7d8d9dadbdcdddedf"`
	`166`	`+"e0e1e2e3e4e5e6e7e8e9eaebecedeeef"`
	`167`	`+"f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";`
`149`	`168`
`150`	`169`	`staticconstint8hexlookup[128]= {`
`151`	`170`	`-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,`
`@@ -165,9 +184,11 @@ hex_encode(const char src, size_t len, char dst)`
`165`	`184`
`166`	`185`	`while (src<end)`
`167`	`186`	`{`
`168`		`-dst++=hextbl[(src >>4)&0xF];`
`169`		`-dst++=hextbl[src&0xF];`
	`187`	`+unsignedcharusrc=((constunsignedchar)src);`
	`188`	`+`
	`189`	`+memcpy(dst,&hextbl[2*usrc],2);`
`170`	`190`	`src++;`
	`191`	`+dst+=2;`
`171`	`192`	`}`
`172`	`193`	`return (uint64)len*2;`
`173`	`194`	`}`

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Commite24d770

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`‎src/backend/utils/adt/encode.c`

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