greenplumn like_match 源码
greenplumn like_match 代码
文件路径：/src/backend/utils/adt/like_match.c
/*-------------------------------------------------------------------------
*
* like_match.c
* LIKE pattern matching internal code.
*
* This file is included by like.c four times, to provide matching code for
* (1) single-byte encodings, (2) UTF8, (3) other multi-byte encodings,
* and (4) case insensitive matches in single-byte encodings.
* (UTF8 is a special case because we can use a much more efficient version
* of NextChar than can be used for general multi-byte encodings.)
*
* Before the inclusion, we need to define the following macros:
*
* NextChar
* MatchText - to name of function wanted
* do_like_escape - name of function if wanted - needs CHAREQ and CopyAdvChar
* MATCH_LOWER - define for case (4) to specify case folding for 1-byte chars
*
* Copyright (c) 1996-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/utils/adt/like_match.c
*
*-------------------------------------------------------------------------
*/
/*
* 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>
*
* SQL 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 pattern, 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.
*--------------------
*/
#ifdef MATCH_LOWER
#define GETCHAR(t) MATCH_LOWER(t)
#else
#define GETCHAR(t) (t)
#endif
static int
MatchText(const char *t, int tlen, const char *p, int plen,
pg_locale_t locale, bool locale_is_c)
{
/* Fast path for match-everything pattern */
if (plen == 1 && *p == '%')
return LIKE_TRUE;
/* Since this function recurses, it could be driven to stack overflow */
check_stack_depth();
/*
* In this loop, we advance by char when matching wildcards (and thus on
* recursive entry to this function we are properly char-synced). On other
* occasions it is safe to advance by byte, as the text and pattern will
* be in lockstep. This allows us to perform all comparisons between the
* text and pattern on a byte by byte basis, even for multi-byte
* encodings.
*/
while (tlen > 0 && plen > 0)
{
if (*p == '\\')
{
/* Next pattern byte must match literally, whatever it is */
NextByte(p, plen);
/* ... and there had better be one, per SQL standard */
if (plen <= 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
errmsg("LIKE pattern must not end with escape character")));
if (GETCHAR(*p) != GETCHAR(*t))
return LIKE_FALSE;
}
else if (*p == '%')
{
char firstpat;
/*
* % processing is essentially a search for a text position at
* which the remainder of the text matches the remainder of the
* pattern, using a recursive call to check each potential match.
*
* If there are wildcards immediately following the %, we can skip
* over them first, using the idea that any sequence of N _'s and
* one or more %'s is equivalent to N _'s and one % (ie, it will
* match any sequence of at least N text characters). In this way
* we will always run the recursive search loop using a pattern
* fragment that begins with a literal character-to-match, thereby
* not recursing more than we have to.
*/
NextByte(p, plen);
while (plen > 0)
{
if (*p == '%')
NextByte(p, plen);
else if (*p == '_')
{
/* If not enough text left to match the pattern, ABORT */
if (tlen <= 0)
return LIKE_ABORT;
NextChar(t, tlen);
NextByte(p, plen);
}
else
break; /* Reached a non-wildcard pattern char */
}
/*
* If we're at end of pattern, match: we have a trailing % which
* matches any remaining text string.
*/
if (plen <= 0)
return LIKE_TRUE;
/*
* Otherwise, scan for a text position at which we can match the
* rest of the pattern. The first remaining pattern char is known
* to be a regular or escaped literal character, so we can compare
* the first pattern byte to each text byte to avoid recursing
* more than we have to. This fact also guarantees that we don't
* have to consider a match to the zero-length substring at the
* end of the text.
*/
if (*p == '\\')
{
if (plen < 2)
ereport(ERROR,
(errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
errmsg("LIKE pattern must not end with escape character")));
firstpat = GETCHAR(p[1]);
}
else
firstpat = GETCHAR(*p);
while (tlen > 0)
{
if (GETCHAR(*t) == firstpat)
{
int matched = MatchText(t, tlen, p, plen,
locale, locale_is_c);
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 == '_')
{
/* _ matches any single character, and we know there is one */
NextChar(t, tlen);
NextByte(p, plen);
continue;
}
else if (GETCHAR(*p) != GETCHAR(*t))
{
/* non-wildcard pattern char fails to match text char */
return LIKE_FALSE;
}
/*
* Pattern and text match, so advance.
*
* It is safe to use NextByte instead of NextChar here, even for
* multi-byte character sets, because we are not following immediately
* after a wildcard character. If we are in the middle of a multibyte
* character, we must already have matched at least one byte of the
* character from both text and pattern; so we cannot get out-of-sync
* on character boundaries. And we know that no backend-legal
* encoding allows ASCII characters such as '%' to appear as non-first
* bytes of characters, so we won't mistakenly detect a new wildcard.
*/
NextByte(t, tlen);
NextByte(p, plen);
}
if (tlen > 0)
return LIKE_FALSE; /* end of pattern, but not of text */
/*
* End of text, but perhaps not of pattern. Match iff the remaining
* pattern can match a zero-length string, ie, it's zero or more %'s.
*/
while (plen > 0 && *p == '%')
NextByte(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() */
/*
* like_escape() --- given a pattern and an ESCAPE string,
* convert the pattern to use Postgres' standard backslash escape convention.
*/
#ifdef do_like_escape
static text *
do_like_escape(text *pat, text *esc)
{
text *result;
char *p,
*e,
*r;
int plen,
elen;
bool afterescape;
p = VARDATA_ANY(pat);
plen = VARSIZE_ANY_EXHDR(pat);
e = VARDATA_ANY(esc);
elen = VARSIZE_ANY_EXHDR(esc);
/*
* 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)
ereport(ERROR,
(errcode(ERRCODE_INVALID_ESCAPE_SEQUENCE),
errmsg("invalid escape string"),
errhint("Escape string must be empty or one character.")));
e = VARDATA_ANY(esc);
/*
* If specified escape is '\', just copy the pattern as-is.
*/
if (*e == '\\')
{
memcpy(result, pat, VARSIZE_ANY(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;
}
}
}
SET_VARSIZE(result, r - ((char *) result));
return result;
}
#endif /* do_like_escape */
#ifdef CHAREQ
#undef CHAREQ
#endif
#undef NextChar
#undef CopyAdvChar
#undef MatchText
#ifdef do_like_escape
#undef do_like_escape
#endif
#undef GETCHAR
#ifdef MATCH_LOWER
#undef MATCH_LOWER
#endif
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