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Commit21d11e7

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Avoid unnecessary copying of source string when generating a cloned TParser.
For long source strings the copying results in O(N^2) behavior, and themultiplier can be significant if wide-char conversion is involved.Andres Freund, reviewed by Kevin Grittner.
1 parenta5495cd commit21d11e7

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1 file changed

+69
-5
lines changed

1 file changed

+69
-5
lines changed

‎src/backend/tsearch/wparser_def.c‎

Lines changed: 69 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
*
88
*
99
* IDENTIFICATION
10-
* $PostgreSQL: pgsql/src/backend/tsearch/wparser_def.c,v 1.25 2009/11/1513:57:01 petere Exp $
10+
* $PostgreSQL: pgsql/src/backend/tsearch/wparser_def.c,v 1.26 2009/12/1520:37:17 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -328,6 +328,46 @@ TParserInit(char *str, int len)
328328
returnprs;
329329
}
330330

331+
/*
332+
* As an alternative to a full TParserInit one can create a
333+
* TParserCopy which basically is a regular TParser without a private
334+
* copy of the string - instead it uses the one from another TParser.
335+
* This is useful because at some places TParsers are created
336+
* recursively and the repeated copying around of the strings can
337+
* cause major inefficiency if the source string is long.
338+
* The new parser starts parsing at the original's current position.
339+
*
340+
* Obviously one must not close the original TParser before the copy.
341+
*/
342+
staticTParser*
343+
TParserCopyInit(constTParser*orig)
344+
{
345+
TParser*prs= (TParser*)palloc0(sizeof(TParser));
346+
347+
prs->charmaxlen=orig->charmaxlen;
348+
prs->str=orig->str+orig->state->posbyte;
349+
prs->lenstr=orig->lenstr-orig->state->posbyte;
350+
351+
#ifdefUSE_WIDE_UPPER_LOWER
352+
prs->usewide=orig->usewide;
353+
354+
if (orig->pgwstr)
355+
prs->pgwstr=orig->pgwstr+orig->state->poschar;
356+
if (orig->wstr)
357+
prs->wstr=orig->wstr+orig->state->poschar;
358+
#endif
359+
360+
prs->state=newTParserPosition(NULL);
361+
prs->state->state=TPS_Base;
362+
363+
#ifdefWPARSER_TRACE
364+
fprintf(stderr,"parsing copy of \"%.*s\"\n",prs->lenstr,prs->str);
365+
#endif
366+
367+
returnprs;
368+
}
369+
370+
331371
staticvoid
332372
TParserClose(TParser*prs)
333373
{
@@ -346,9 +386,33 @@ TParserClose(TParser *prs)
346386
pfree(prs->pgwstr);
347387
#endif
348388

389+
#ifdefWPARSER_TRACE
390+
fprintf(stderr,"closing parser");
391+
#endif
349392
pfree(prs);
350393
}
351394

395+
/*
396+
* Close a parser created with TParserCopyInit
397+
*/
398+
staticvoid
399+
TParserCopyClose(TParser*prs)
400+
{
401+
while (prs->state)
402+
{
403+
TParserPosition*ptr=prs->state->prev;
404+
405+
pfree(prs->state);
406+
prs->state=ptr;
407+
}
408+
409+
#ifdefWPARSER_TRACE
410+
fprintf(stderr,"closing parser copy");
411+
#endif
412+
pfree(prs);
413+
}
414+
415+
352416
/*
353417
* Character-type support functions, equivalent to is* macros, but
354418
* working with any possible encodings and locales. Notes:
@@ -617,7 +681,7 @@ p_isignore(TParser *prs)
617681
staticint
618682
p_ishost(TParser*prs)
619683
{
620-
TParser*tmpprs=TParserInit(prs->str+prs->state->posbyte,prs->lenstr-prs->state->posbyte);
684+
TParser*tmpprs=TParserCopyInit(prs);
621685
intres=0;
622686

623687
tmpprs->wanthost= true;
@@ -631,15 +695,15 @@ p_ishost(TParser *prs)
631695
prs->state->charlen=tmpprs->state->charlen;
632696
res=1;
633697
}
634-
TParserClose(tmpprs);
698+
TParserCopyClose(tmpprs);
635699

636700
returnres;
637701
}
638702

639703
staticint
640704
p_isURLPath(TParser*prs)
641705
{
642-
TParser*tmpprs=TParserInit(prs->str+prs->state->posbyte,prs->lenstr-prs->state->posbyte);
706+
TParser*tmpprs=TParserCopyInit(prs);
643707
intres=0;
644708

645709
tmpprs->state=newTParserPosition(tmpprs->state);
@@ -654,7 +718,7 @@ p_isURLPath(TParser *prs)
654718
prs->state->charlen=tmpprs->state->charlen;
655719
res=1;
656720
}
657-
TParserClose(tmpprs);
721+
TParserCopyClose(tmpprs);
658722

659723
returnres;
660724
}

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