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Commitb31e3f5

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Improve worst-case performance of text_position_get_match_pos()
This function converts a byte position to a character position aftera successful string match. Rather than calling pg_mblen() in a loop,use pg_mbstrlen_with_len() since the latter can inline its own call topg_mblen(). When the string match is at the end of the haystack text, thischange results in 10-20% performance improvement, depending on platform andtypical character length in bytes. This also simplifies the code a little.Specializing for UTF-8 could result in further improvement, but theperformance gain was not found to be reliable between platforms. The modestgain in this commit is stable between platforms and usable by all serverencodings.Discussion:https://www.postgresql.org/message-id/CAFBsxsH1Yutrmu+6LLHKK8iXY+vG--Do6zN+2900spHXQNNQKQ@mail.gmail.com
1 parent807fee1 commitb31e3f5

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‎src/backend/utils/adt/varlena.c

Lines changed: 5 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -51,7 +51,6 @@ typedef struct varlena VarString;
5151
*/
5252
typedefstruct
5353
{
54-
boolis_multibyte;/* T if multibyte encoding */
5554
boolis_multibyte_char_in_char;/* need to check char boundaries? */
5655

5756
char*str1;/* haystack string */
@@ -1221,20 +1220,11 @@ text_position_setup(text *t1, text *t2, Oid collid, TextPositionState *state)
12211220
* and continue the search if it was a false match.
12221221
*/
12231222
if (pg_database_encoding_max_length()==1)
1224-
{
1225-
state->is_multibyte= false;
12261223
state->is_multibyte_char_in_char= false;
1227-
}
12281224
elseif (GetDatabaseEncoding()==PG_UTF8)
1229-
{
1230-
state->is_multibyte= true;
12311225
state->is_multibyte_char_in_char= false;
1232-
}
12331226
else
1234-
{
1235-
state->is_multibyte= true;
12361227
state->is_multibyte_char_in_char= true;
1237-
}
12381228

12391229
state->str1=VARDATA_ANY(t1);
12401230
state->str2=VARDATA_ANY(t2);
@@ -1466,19 +1456,11 @@ text_position_get_match_ptr(TextPositionState *state)
14661456
staticint
14671457
text_position_get_match_pos(TextPositionState*state)
14681458
{
1469-
if (!state->is_multibyte)
1470-
returnstate->last_match-state->str1+1;
1471-
else
1472-
{
1473-
/* Convert the byte position to char position. */
1474-
while (state->refpoint<state->last_match)
1475-
{
1476-
state->refpoint+=pg_mblen(state->refpoint);
1477-
state->refpos++;
1478-
}
1479-
Assert(state->refpoint==state->last_match);
1480-
returnstate->refpos+1;
1481-
}
1459+
/* Convert the byte position to char position. */
1460+
state->refpos+=pg_mbstrlen_with_len(state->refpoint,
1461+
state->last_match-state->refpoint);
1462+
state->refpoint=state->last_match;
1463+
returnstate->refpos+1;
14821464
}
14831465

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/*

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