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Commitcc39aca

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Fix similar_escape() so that SIMILAR TO works properly for patterns involving
alternatives ("|" symbol). The original coding allowed the added ^ and $constraints to be absorbed into the first and last alternatives, producinga pattern that would match more than it should. Per report from Eric Noriega.I also changed the pattern to add an ARE director ("***:"), ensuring thatSIMILAR TO patterns do not change behavior if regex_flavor is changed. Thisis necessary to make the non-capturing parentheses work, and seems like agood idea on general principles.Back-patched as far as 7.4. 7.3 also has the bug, but a fix seems impracticalbecause that version's regex engine doesn't have non-capturing parens.
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‎src/backend/utils/adt/regexp.c

Lines changed: 29 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
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*
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* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.62 2006/03/05 15:58:43 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.63 2006/04/13 18:01:31 tgl Exp $
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*
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*Alistair Crooks added the code for the regex caching
1414
*agc - cached the regular expressions used - there's a good chance
@@ -549,11 +549,36 @@ similar_escape(PG_FUNCTION_ARGS)
549549
errhint("Escape string must be empty or one character.")));
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}
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/* We need room for ^, $, and up to 2 output bytes per input byte */
553-
result= (text*)palloc(VARHDRSZ+2+2*plen);
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/*----------
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* We surround the transformed input string with
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****:^(?: ... )$
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* which is bizarre enough to require some explanation. "***:" is a
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* director prefix to force the regex to be treated as an ARE regardless
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* of the current regex_flavor setting. We need "^" and "$" to force
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* the pattern to match the entire input string as per SQL99 spec. The
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* "(?:" and ")" are a non-capturing set of parens; we have to have
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* parens in case the string contains "|", else the "^" and "$" will
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* be bound into the first and last alternatives which is not what we
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* want, and the parens must be non capturing because we don't want them
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* to count when selecting output for SUBSTRING.
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*----------
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*/
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/*
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* We need room for the prefix/postfix plus as many as 2 output bytes per
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* input byte
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*/
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result= (text*)palloc(VARHDRSZ+10+2*plen);
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r=VARDATA(result);
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*r++='*';
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*r++='*';
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*r++='*';
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*r++=':';
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*r++='^';
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*r++='(';
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*r++='?';
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*r++=':';
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while (plen>0)
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{
@@ -593,6 +618,7 @@ similar_escape(PG_FUNCTION_ARGS)
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p++,plen--;
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}
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621+
*r++=')';
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*r++='$';
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VARATT_SIZEP(result)=r- ((char*)result);

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