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Commitb14b1eb

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Teach convert() and friends to avoid copying when possible.
Presently, pg_convert() allocates a new bytea and copies the resultregardless of whether any conversion actually happened. Thiscommit adjusts this function to return the source pointer as-is ifno conversion occurred. This optimization isn't expected to make atremendous difference, but it still seems worthwhile to avoidunnecessary memory allocations.Author: Yurii RashkovskiiReviewed-by: Bertrand DrouvotDiscussion:https://postgr.es/m/CA%2BRLCQyknBPSWXRBQGOi6aYEcdQ9RpH9Kch4GjoeY8dQ3D%2Bvhw%40mail.gmail.com
1 parente7c6efe commitb14b1eb

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‎src/backend/utils/mb/mbutils.c

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -585,19 +585,19 @@ pg_convert(PG_FUNCTION_ARGS)
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src_encoding,
586586
dest_encoding);
587587

588-
/* update len if conversion actually happened */
589-
if (dest_str!=src_str)
590-
len=strlen(dest_str);
588+
589+
/* return source string if no conversion happened */
590+
if (dest_str==src_str)
591+
PG_RETURN_BYTEA_P(string);
591592

592593
/*
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* build bytea data type structure.
594595
*/
596+
len=strlen(dest_str);
595597
retval= (bytea*)palloc(len+VARHDRSZ);
596598
SET_VARSIZE(retval,len+VARHDRSZ);
597599
memcpy(VARDATA(retval),dest_str,len);
598-
599-
if (dest_str!=src_str)
600-
pfree(dest_str);
600+
pfree(dest_str);
601601

602602
/* free memory if allocated by the toaster */
603603
PG_FREE_IF_COPY(string,0);

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