From 219bd1e4fb920c6af5d789aab9e5eafa674c7364 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 4 Oct 2001 02:15:47 +0000
Subject: [PATCH] Optimization for single byte encodings.
---
src/backend/utils/adt/like.c | 408 +++++++----------------------
src/backend/utils/adt/like_match.c | 339 ++++++++++++++++++++++++
2 files changed, 433 insertions(+), 314 deletions(-)
create mode 100644 src/backend/utils/adt/like_match.c
diff --git a/src/backend/utils/adt/like.c b/src/backend/utils/adt/like.c
index 4f6d6d0212b..f3f8b9854e1 100644
--- a/src/backend/utils/adt/like.c
+++ b/src/backend/utils/adt/like.c
@@ -11,7 +11,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/like.c,v 1.46 2001/09/14 17:46:40 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/like.c,v 1.47 2001/10/04 02:15:47 ishii Exp $
*
*-------------------------------------------------------------------------
*/
@@ -36,9 +36,15 @@ static int MatchTextIC(unsigned char *t, int tlen,
unsigned char *p, int plen);
static int MatchBytea(unsigned char *t, int tlen,
unsigned char *p, int plen);
-
+static text *do_like_escape(text *, text *);
#ifdef MULTIBYTE
+static int MBMatchText(unsigned char *t, int tlen,
+ unsigned char *p, int plen);
+static int MBMatchTextIC(unsigned char *t, int tlen,
+ unsigned char *p, int plen);
+static text *MB_do_like_escape(text *, text *);
+
/*--------------------
* Support routine for MatchText. Compares given multibyte streams
* as wide characters. If they match, returns 1 otherwise returns 0.
@@ -115,16 +121,29 @@ iwchareq(unsigned char *p1, unsigned char *p2)
while (__l-- > 0) \
*(dst)++ = *(src)++; \
} while (0)
-#else
+
+#define MatchText MBMatchText
+#define MatchTextIC MBMatchTextIC
+#define do_like_escape MB_do_like_escape
+#include "like_match.c"
+#undef CHAREQ
+#undef ICHAREQ
+#undef NextChar
+#undef CopyAdvChar
+#undef MatchText
+#undef MatchTextIC
+#undef do_like_escape
+#endif
+
#define CHAREQ(p1, p2) (*(p1) == *(p2))
#define ICHAREQ(p1, p2) (tolower(*(p1)) == tolower(*(p2)))
#define NextChar(p, plen) ((p)++, (plen)--)
#define CopyAdvChar(dst, src, srclen) (*(dst)++ = *(src)++, (srclen)--)
-#endif
#define BYTEA_CHAREQ(p1, p2) (*(p1) == *(p2))
#define BYTEA_NextChar(p, plen) ((p)++, (plen)--)
#define BYTEA_CopyAdvChar(dst, src, srclen) (*(dst)++ = *(src)++, (srclen)--)
+#include "like_match.c"
/*
* interface routines called by the function manager
@@ -146,7 +165,14 @@ namelike(PG_FUNCTION_ARGS)
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
+ else
+ result = (MBMatchText(s, slen, p, plen) == LIKE_TRUE);
+#else
+ result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -167,7 +193,14 @@ namenlike(PG_FUNCTION_ARGS)
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
+ else
+ result = (MBMatchText(s, slen, p, plen) != LIKE_TRUE);
+#else
+ result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -182,13 +215,19 @@ textlike(PG_FUNCTION_ARGS)
*p;
int slen,
plen;
-
s = VARDATA(str);
slen = (VARSIZE(str) - VARHDRSZ);
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
+ else
+ result = (MBMatchText(s, slen, p, plen) == LIKE_TRUE);
+#else
+ result = (MatchText(s, slen, p, plen) == LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -209,7 +248,14 @@ textnlike(PG_FUNCTION_ARGS)
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
+ else
+ result = (MBMatchText(s, slen, p, plen) != LIKE_TRUE);
+#else
+ result = (MatchText(s, slen, p, plen) != LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -276,7 +322,14 @@ nameiclike(PG_FUNCTION_ARGS)
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+ else
+ result = (MBMatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+#else
+ result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -297,7 +350,14 @@ nameicnlike(PG_FUNCTION_ARGS)
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+ else
+ result = (MBMatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+#else
+ result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -318,7 +378,14 @@ texticlike(PG_FUNCTION_ARGS)
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+ else
+ result = (MBMatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+#else
+ result = (MatchTextIC(s, slen, p, plen) == LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -339,7 +406,14 @@ texticnlike(PG_FUNCTION_ARGS)
p = VARDATA(pat);
plen = (VARSIZE(pat) - VARHDRSZ);
- result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+ else
+ result = (MBMatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+#else
+ result = (MatchTextIC(s, slen, p, plen) != LIKE_TRUE);
+#endif
PG_RETURN_BOOL(result);
}
@@ -354,90 +428,15 @@ like_escape(PG_FUNCTION_ARGS)
text *pat = PG_GETARG_TEXT_P(0);
text *esc = PG_GETARG_TEXT_P(1);
text *result;
- unsigned char *p,
- *e,
- *r;
- int plen,
- elen;
- bool afterescape;
-
- p = VARDATA(pat);
- plen = (VARSIZE(pat) - VARHDRSZ);
- e = VARDATA(esc);
- elen = (VARSIZE(esc) - VARHDRSZ);
- /*
- * Worst-case pattern growth is 2x --- unlikely, but it's hardly worth
- * trying to calculate the size more accurately than that.
- */
- result = (text *) palloc(plen * 2 + VARHDRSZ);
- r = VARDATA(result);
-
- if (elen == 0)
- {
-
- /*
- * No escape character is wanted. Double any backslashes in the
- * pattern to make them act like ordinary characters.
- */
- while (plen > 0)
- {
- if (*p == '\\')
- *r++ = '\\';
- CopyAdvChar(r, p, plen);
- }
- }
+#ifdef MULTIBYTE
+ if (pg_database_encoding_max_length() == 1)
+ result = do_like_escape(pat, esc);
else
- {
-
- /*
- * The specified escape must be only a single character.
- */
- NextChar(e, elen);
- if (elen != 0)
- elog(ERROR, "ESCAPE string must be empty or one character");
- e = VARDATA(esc);
-
- /*
- * If specified escape is '\', just copy the pattern as-is.
- */
- if (*e == '\\')
- {
- memcpy(result, pat, VARSIZE(pat));
- PG_RETURN_TEXT_P(result);
- }
-
- /*
- * Otherwise, convert occurrences of the specified escape
- * character to '\', and double occurrences of '\' --- unless they
- * immediately follow an escape character!
- */
- afterescape = false;
- while (plen > 0)
- {
- if (CHAREQ(p, e) && !afterescape)
- {
- *r++ = '\\';
- NextChar(p, plen);
- afterescape = true;
- }
- else if (*p == '\\')
- {
- *r++ = '\\';
- if (!afterescape)
- *r++ = '\\';
- NextChar(p, plen);
- afterescape = false;
- }
- else
- {
- CopyAdvChar(r, p, plen);
- afterescape = false;
- }
- }
- }
-
- VARATT_SIZEP(result) = r - ((unsigned char *) result);
+ result = MB_do_like_escape(pat, esc);
+#else
+ result = do_like_escape(pat, esc);
+#endif
PG_RETURN_TEXT_P(result);
}
@@ -540,225 +539,6 @@ like_escape_bytea(PG_FUNCTION_ARGS)
PG_RETURN_BYTEA_P(result);
}
-/*
-** Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
-** Rich $alz is now <rsalz@bbn.com>.
-** Special thanks to Lars Mathiesen <thorinn@diku.dk> for the LABORT code.
-**
-** This code was shamelessly stolen from the "pql" code by myself and
-** slightly modified :)
-**
-** All references to the word "star" were replaced by "percent"
-** All references to the word "wild" were replaced by "like"
-**
-** All the nice shell RE matching stuff was replaced by just "_" and "%"
-**
-** As I don't have a copy of the SQL standard handy I wasn't sure whether
-** to leave in the '\' escape character handling.
-**
-** Keith Parks. <keith@mtcc.demon.co.uk>
-**
-** SQL92 lets you specify the escape character by saying
-** LIKE <pattern> ESCAPE <escape character>. We are a small operation
-** so we force you to use '\'. - ay 7/95
-**
-** Now we have the like_escape() function that converts patterns with
-** any specified escape character (or none at all) to the internal
-** default escape character, which is still '\'. - tgl 9/2000
-**
-** The code is rewritten to avoid requiring null-terminated strings,
-** which in turn allows us to leave out some memcpy() operations.
-** This code should be faster and take less memory, but no promises...
-** - thomas 2000-08-06
-**
-*/
-
-
-/*--------------------
- * Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
- *
- * LIKE_TRUE: they match
- * LIKE_FALSE: they don't match
- * LIKE_ABORT: not only don't they match, but the text is too short.
- *
- * If LIKE_ABORT is returned, then no suffix of the text can match the
- * pattern either, so an upper-level % scan can stop scanning now.
- *--------------------
- */
-
-static int
-MatchText(unsigned char *t, int tlen, unsigned char *p, int plen)
-{
- /* Fast path for match-everything pattern */
- if ((plen == 1) && (*p == '%'))
- return LIKE_TRUE;
-
- while ((tlen > 0) && (plen > 0))
- {
- if (*p == '\\')
- {
- /* Next pattern char must match literally, whatever it is */
- NextChar(p, plen);
- if ((plen <= 0) || !CHAREQ(t, p))
- return LIKE_FALSE;
- }
- else if (*p == '%')
- {
- /* %% is the same as % according to the SQL standard */
- /* Advance past all %'s */
- while ((plen > 0) && (*p == '%'))
- NextChar(p, plen);
- /* Trailing percent matches everything. */
- if (plen <= 0)
- return LIKE_TRUE;
-
- /*
- * Otherwise, scan for a text position at which we can match
- * the rest of the pattern.
- */
- while (tlen > 0)
- {
-
- /*
- * Optimization to prevent most recursion: don't recurse
- * unless first pattern char might match this text char.
- */
- if (CHAREQ(t, p) || (*p == '\\') || (*p == '_'))
- {
- int matched = MatchText(t, tlen, p, plen);
-
- if (matched != LIKE_FALSE)
- return matched; /* TRUE or ABORT */
- }
-
- NextChar(t, tlen);
- }
-
- /*
- * End of text with no match, so no point in trying later
- * places to start matching this pattern.
- */
- return LIKE_ABORT;
- }
- else if ((*p != '_') && !CHAREQ(t, p))
- {
-
- /*
- * Not the single-character wildcard and no explicit match?
- * Then time to quit...
- */
- return LIKE_FALSE;
- }
-
- NextChar(t, tlen);
- NextChar(p, plen);
- }
-
- if (tlen > 0)
- return LIKE_FALSE; /* end of pattern, but not of text */
-
- /* End of input string. Do we have matching pattern remaining? */
- while ((plen > 0) && (*p == '%')) /* allow multiple %'s at end of
- * pattern */
- NextChar(p, plen);
- if (plen <= 0)
- return LIKE_TRUE;
-
- /*
- * End of text with no match, so no point in trying later places to
- * start matching this pattern.
- */
- return LIKE_ABORT;
-} /* MatchText() */
-
-/*
- * Same as above, but ignore case
- */
-static int
-MatchTextIC(unsigned char *t, int tlen, unsigned char *p, int plen)
-{
- /* Fast path for match-everything pattern */
- if ((plen == 1) && (*p == '%'))
- return LIKE_TRUE;
-
- while ((tlen > 0) && (plen > 0))
- {
- if (*p == '\\')
- {
- /* Next pattern char must match literally, whatever it is */
- NextChar(p, plen);
- if ((plen <= 0) || !ICHAREQ(t, p))
- return LIKE_FALSE;
- }
- else if (*p == '%')
- {
- /* %% is the same as % according to the SQL standard */
- /* Advance past all %'s */
- while ((plen > 0) && (*p == '%'))
- NextChar(p, plen);
- /* Trailing percent matches everything. */
- if (plen <= 0)
- return LIKE_TRUE;
-
- /*
- * Otherwise, scan for a text position at which we can match
- * the rest of the pattern.
- */
- while (tlen > 0)
- {
-
- /*
- * Optimization to prevent most recursion: don't recurse
- * unless first pattern char might match this text char.
- */
- if (ICHAREQ(t, p) || (*p == '\\') || (*p == '_'))
- {
- int matched = MatchTextIC(t, tlen, p, plen);
-
- if (matched != LIKE_FALSE)
- return matched; /* TRUE or ABORT */
- }
-
- NextChar(t, tlen);
- }
-
- /*
- * End of text with no match, so no point in trying later
- * places to start matching this pattern.
- */
- return LIKE_ABORT;
- }
- else if ((*p != '_') && !ICHAREQ(t, p))
- {
-
- /*
- * Not the single-character wildcard and no explicit match?
- * Then time to quit...
- */
- return LIKE_FALSE;
- }
-
- NextChar(t, tlen);
- NextChar(p, plen);
- }
-
- if (tlen > 0)
- return LIKE_FALSE; /* end of pattern, but not of text */
-
- /* End of input string. Do we have matching pattern remaining? */
- while ((plen > 0) && (*p == '%')) /* allow multiple %'s at end of
- * pattern */
- NextChar(p, plen);
- if (plen <= 0)
- return LIKE_TRUE;
-
- /*
- * End of text with no match, so no point in trying later places to
- * start matching this pattern.
- */
- return LIKE_ABORT;
-} /* MatchTextIC() */
-
/*
* Same as above, but specifically for bytea (binary) datatype
*/
diff --git a/src/backend/utils/adt/like_match.c b/src/backend/utils/adt/like_match.c
new file mode 100644
index 00000000000..f13b8fea05c
--- /dev/null
+++ b/src/backend/utils/adt/like_match.c
@@ -0,0 +1,339 @@
+/*-------------------------------------------------------------------------
+ *
+ * like_match.c
+ * like expression handling internal code.
+ *
+ * This file is included by like.c *twice* if multibyte is enabled.
+ * This is for an optimization of single byte encodings.
+ * Before the inclusion, we need to define following macros:
+ *
+ * CHAREQ
+ * ICHAREQ
+ * NextChar
+ * CopyAdvChar
+ * MatchText (MBMatchText)
+ * MatchTextIC (MBMatchTextIC)
+ * do_like_escape (MB_do_like_escape)
+ *
+ * Copyright (c) 1996-2001, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/like_match.c,v 1.1 2001/10/04 02:15:47 ishii Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/*
+** Originally written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
+** Rich $alz is now <rsalz@bbn.com>.
+** Special thanks to Lars Mathiesen <thorinn@diku.dk> for the LABORT code.
+**
+** This code was shamelessly stolen from the "pql" code by myself and
+** slightly modified :)
+**
+** All references to the word "star" were replaced by "percent"
+** All references to the word "wild" were replaced by "like"
+**
+** All the nice shell RE matching stuff was replaced by just "_" and "%"
+**
+** As I don't have a copy of the SQL standard handy I wasn't sure whether
+** to leave in the '\' escape character handling.
+**
+** Keith Parks. <keith@mtcc.demon.co.uk>
+**
+** SQL92 lets you specify the escape character by saying
+** LIKE <pattern> ESCAPE <escape character>. We are a small operation
+** so we force you to use '\'. - ay 7/95
+**
+** Now we have the like_escape() function that converts patterns with
+** any specified escape character (or none at all) to the internal
+** default escape character, which is still '\'. - tgl 9/2000
+**
+** The code is rewritten to avoid requiring null-terminated strings,
+** which in turn allows us to leave out some memcpy() operations.
+** This code should be faster and take less memory, but no promises...
+** - thomas 2000-08-06
+**
+*/
+
+
+/*--------------------
+ * Match text and p, return LIKE_TRUE, LIKE_FALSE, or LIKE_ABORT.
+ *
+ * LIKE_TRUE: they match
+ * LIKE_FALSE: they don't match
+ * LIKE_ABORT: not only don't they match, but the text is too short.
+ *
+ * If LIKE_ABORT is returned, then no suffix of the text can match the
+ * pattern either, so an upper-level % scan can stop scanning now.
+ *--------------------
+ */
+
+static int
+MatchText(unsigned char *t, int tlen, unsigned char *p, int plen)
+{
+ /* Fast path for match-everything pattern */
+ if ((plen == 1) && (*p == '%'))
+ return LIKE_TRUE;
+
+ while ((tlen > 0) && (plen > 0))
+ {
+ if (*p == '\\')
+ {
+ /* Next pattern char must match literally, whatever it is */
+ NextChar(p, plen);
+ if ((plen <= 0) || !CHAREQ(t, p))
+ return LIKE_FALSE;
+ }
+ else if (*p == '%')
+ {
+ /* %% is the same as % according to the SQL standard */
+ /* Advance past all %'s */
+ while ((plen > 0) && (*p == '%'))
+ NextChar(p, plen);
+ /* Trailing percent matches everything. */
+ if (plen <= 0)
+ return LIKE_TRUE;
+
+ /*
+ * Otherwise, scan for a text position at which we can match
+ * the rest of the pattern.
+ */
+ while (tlen > 0)
+ {
+
+ /*
+ * Optimization to prevent most recursion: don't recurse
+ * unless first pattern char might match this text char.
+ */
+ if (CHAREQ(t, p) || (*p == '\\') || (*p == '_'))
+ {
+ int matched = MatchText(t, tlen, p, plen);
+
+ if (matched != LIKE_FALSE)
+ return matched; /* TRUE or ABORT */
+ }
+
+ NextChar(t, tlen);
+ }
+
+ /*
+ * End of text with no match, so no point in trying later
+ * places to start matching this pattern.
+ */
+ return LIKE_ABORT;
+ }
+ else if ((*p != '_') && !CHAREQ(t, p))
+ {
+
+ /*
+ * Not the single-character wildcard and no explicit match?
+ * Then time to quit...
+ */
+ return LIKE_FALSE;
+ }
+
+ NextChar(t, tlen);
+ NextChar(p, plen);
+ }
+
+ if (tlen > 0)
+ return LIKE_FALSE; /* end of pattern, but not of text */
+
+ /* End of input string. Do we have matching pattern remaining? */
+ while ((plen > 0) && (*p == '%')) /* allow multiple %'s at end of
+ * pattern */
+ NextChar(p, plen);
+ if (plen <= 0)
+ return LIKE_TRUE;
+
+ /*
+ * End of text with no match, so no point in trying later places to
+ * start matching this pattern.
+ */
+ return LIKE_ABORT;
+} /* MatchText() */
+
+/*
+ * Same as above, but ignore case
+ */
+static int
+MatchTextIC(unsigned char *t, int tlen, unsigned char *p, int plen)
+{
+ /* Fast path for match-everything pattern */
+ if ((plen == 1) && (*p == '%'))
+ return LIKE_TRUE;
+
+ while ((tlen > 0) && (plen > 0))
+ {
+ if (*p == '\\')
+ {
+ /* Next pattern char must match literally, whatever it is */
+ NextChar(p, plen);
+ if ((plen <= 0) || !ICHAREQ(t, p))
+ return LIKE_FALSE;
+ }
+ else if (*p == '%')
+ {
+ /* %% is the same as % according to the SQL standard */
+ /* Advance past all %'s */
+ while ((plen > 0) && (*p == '%'))
+ NextChar(p, plen);
+ /* Trailing percent matches everything. */
+ if (plen <= 0)
+ return LIKE_TRUE;
+
+ /*
+ * Otherwise, scan for a text position at which we can match
+ * the rest of the pattern.
+ */
+ while (tlen > 0)
+ {
+
+ /*
+ * Optimization to prevent most recursion: don't recurse
+ * unless first pattern char might match this text char.
+ */
+ if (ICHAREQ(t, p) || (*p == '\\') || (*p == '_'))
+ {
+ int matched = MatchTextIC(t, tlen, p, plen);
+
+ if (matched != LIKE_FALSE)
+ return matched; /* TRUE or ABORT */
+ }
+
+ NextChar(t, tlen);
+ }
+
+ /*
+ * End of text with no match, so no point in trying later
+ * places to start matching this pattern.
+ */
+ return LIKE_ABORT;
+ }
+ else if ((*p != '_') && !ICHAREQ(t, p))
+ {
+
+ /*
+ * Not the single-character wildcard and no explicit match?
+ * Then time to quit...
+ */
+ return LIKE_FALSE;
+ }
+
+ NextChar(t, tlen);
+ NextChar(p, plen);
+ }
+
+ if (tlen > 0)
+ return LIKE_FALSE; /* end of pattern, but not of text */
+
+ /* End of input string. Do we have matching pattern remaining? */
+ while ((plen > 0) && (*p == '%')) /* allow multiple %'s at end of
+ * pattern */
+ NextChar(p, plen);
+ if (plen <= 0)
+ return LIKE_TRUE;
+
+ /*
+ * End of text with no match, so no point in trying later places to
+ * start matching this pattern.
+ */
+ return LIKE_ABORT;
+} /* MatchTextIC() */
+
+/*
+ * like_escape() --- given a pattern and an ESCAPE string,
+ * convert the pattern to use Postgres' standard backslash escape convention.
+ */
+static text *
+do_like_escape(text *pat, text *esc)
+{
+ text *result;
+ unsigned char *p,
+ *e,
+ *r;
+ int plen,
+ elen;
+ bool afterescape;
+
+ p = VARDATA(pat);
+ plen = (VARSIZE(pat) - VARHDRSZ);
+ e = VARDATA(esc);
+ elen = (VARSIZE(esc) - VARHDRSZ);
+
+ /*
+ * Worst-case pattern growth is 2x --- unlikely, but it's hardly worth
+ * trying to calculate the size more accurately than that.
+ */
+ result = (text *) palloc(plen * 2 + VARHDRSZ);
+ r = VARDATA(result);
+
+ if (elen == 0)
+ {
+
+ /*
+ * No escape character is wanted. Double any backslashes in the
+ * pattern to make them act like ordinary characters.
+ */
+ while (plen > 0)
+ {
+ if (*p == '\\')
+ *r++ = '\\';
+ CopyAdvChar(r, p, plen);
+ }
+ }
+ else
+ {
+
+ /*
+ * The specified escape must be only a single character.
+ */
+ NextChar(e, elen);
+ if (elen != 0)
+ elog(ERROR, "ESCAPE string must be empty or one character");
+ e = VARDATA(esc);
+
+ /*
+ * If specified escape is '\', just copy the pattern as-is.
+ */
+ if (*e == '\\')
+ {
+ memcpy(result, pat, VARSIZE(pat));
+ return result;
+ }
+
+ /*
+ * Otherwise, convert occurrences of the specified escape
+ * character to '\', and double occurrences of '\' --- unless they
+ * immediately follow an escape character!
+ */
+ afterescape = false;
+ while (plen > 0)
+ {
+ if (CHAREQ(p, e) && !afterescape)
+ {
+ *r++ = '\\';
+ NextChar(p, plen);
+ afterescape = true;
+ }
+ else if (*p == '\\')
+ {
+ *r++ = '\\';
+ if (!afterescape)
+ *r++ = '\\';
+ NextChar(p, plen);
+ afterescape = false;
+ }
+ else
+ {
+ CopyAdvChar(r, p, plen);
+ afterescape = false;
+ }
+ }
+ }
+
+ VARATT_SIZEP(result) = r - ((unsigned char *) result);
+
+ return result;
+}
--
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