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Back-patch fix for extraction of fixed prefixes from regular expressions.

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Back-patch of commits 628cbb50ba and
c6aae3042b.  This has been broken since
7.3, so back-patch to all supported branches.
This commit is contained in:
Tom Lane
2012-07-10 18:00:47 -04:00
parent 647ae3cfe3
commit dffc6c8a85
11 changed files with 429 additions and 196 deletions
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208
src/backend/utils/adt/selfuncs.c
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@ -178,7 +178,8 @@ static Selectivity prefix_selectivity(PlannerInfo *root,
static Selectivity like_selectivity(const char *patt, int pattlen,
bool case_insensitive);
static Selectivity regex_selectivity(const char *patt, int pattlen,
bool case_insensitive);
bool case_insensitive,
int fixed_prefix_len);
static Datum string_to_datum(const char *str, Oid datatype);
static Const *string_to_const(const char *str, Oid datatype);
static Const *string_to_bytea_const(const char *str, size_t str_len);
@ -4922,16 +4923,9 @@ static Pattern_Prefix_Status
regex_fixed_prefix(Const *patt_const, bool case_insensitive,
Const **prefix_const, Selectivity *rest_selec)
{
char *match;
int pos,
match_pos,
prev_pos,
prev_match_pos;
bool have_leading_paren;
char *patt;
char *rest;
Oid typeid = patt_const->consttype;
bool is_multibyte = (pg_database_encoding_max_length() > 1);
char *prefix;
bool exact;
/*
* Should be unnecessary, there are no bytea regex operators defined. As
@ -4943,170 +4937,54 @@ regex_fixed_prefix(Const *patt_const, bool case_insensitive,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("regular-expression matching not supported on type bytea")));
/* the right-hand const is type text for all of these */
patt = TextDatumGetCString(patt_const->constvalue);
/* Use the regexp machinery to extract the prefix, if any */
prefix = regexp_fixed_prefix(DatumGetTextPP(patt_const->constvalue),
case_insensitive,
&exact);
/*
* Check for ARE director prefix. It's worth our trouble to recognize
* this because similar_escape() used to use it, and some other code might
* still use it, to force ARE mode.
*/
pos = 0;
if (strncmp(patt, "***:", 4) == 0)
pos = 4;
/* Pattern must be anchored left */
if (patt[pos] != '^')
if (prefix == NULL)
{
*prefix_const = NULL;
if (rest_selec != NULL)
{
char *patt = TextDatumGetCString(patt_const->constvalue);
*rest_selec = regex_selectivity(patt, strlen(patt),
case_insensitive);
return Pattern_Prefix_None;
}
pos++;
/*
* If '|' is present in pattern, then there may be multiple alternatives
* for the start of the string. (There are cases where this isn't so, for
* instance if the '|' is inside parens, but detecting that reliably is
* too hard.)
*/
if (strchr(patt + pos, '|') != NULL)
{
*prefix_const = NULL;
if (rest_selec != NULL)
*rest_selec = regex_selectivity(patt, strlen(patt),
case_insensitive);
case_insensitive,
0);
pfree(patt);
}
return Pattern_Prefix_None;
}
/* OK, allocate space for pattern */
match = palloc(strlen(patt) + 1);
prev_match_pos = match_pos = 0;
/*
* We special-case the syntax '^(...)$' because psql uses it. But beware:
* sequences beginning "(?" are not what they seem, unless they're "(?:".
* (We must recognize that because of similar_escape().)
*/
have_leading_paren = false;
if (patt[pos] == '(' &&
(patt[pos + 1] != '?' || patt[pos + 2] == ':'))
{
have_leading_paren = true;
pos += (patt[pos + 1] != '?' ? 1 : 3);
}
/* Scan remainder of pattern */
prev_pos = pos;
while (patt[pos])
{
int len;
/*
* Check for characters that indicate multiple possible matches here.
* Also, drop out at ')' or '$' so the termination test works right.
*/
if (patt[pos] == '.' ||
patt[pos] == '(' ||
patt[pos] == ')' ||
patt[pos] == '[' ||
patt[pos] == '^' ||
patt[pos] == '$')
break;
/*
* XXX In multibyte character sets, we can't trust isalpha, so assume
* any multibyte char is potentially case-varying.
*/
if (case_insensitive)
{
if (is_multibyte && (unsigned char) patt[pos] >= 0x80)
break;
if (isalpha((unsigned char) patt[pos]))
break;
}
/*
* Check for quantifiers. Except for +, this means the preceding
* character is optional, so we must remove it from the prefix too!
*/
if (patt[pos] == '*' ||
patt[pos] == '?' ||
patt[pos] == '{')
{
match_pos = prev_match_pos;
pos = prev_pos;
break;
}
if (patt[pos] == '+')
{
pos = prev_pos;
break;
}
/*
* Normally, backslash quotes the next character. But in AREs,
* backslash followed by alphanumeric is an escape, not a quoted
* character. Must treat it as having multiple possible matches.
* Note: since only ASCII alphanumerics are escapes, we don't have to
* be paranoid about multibyte here.
*/
if (patt[pos] == '\\')
{
if (isalnum((unsigned char) patt[pos + 1]))
break;
pos++;
if (patt[pos] == '\0')
break;
}
/* save position in case we need to back up on next loop cycle */
prev_match_pos = match_pos;
prev_pos = pos;
/* must use encoding-aware processing here */
len = pg_mblen(&patt[pos]);
memcpy(&match[match_pos], &patt[pos], len);
match_pos += len;
pos += len;
}
match[match_pos] = '\0';
rest = &patt[pos];
if (have_leading_paren && patt[pos] == ')')
pos++;
if (patt[pos] == '$' && patt[pos + 1] == '\0')
{
*prefix_const = string_to_const(match, typeid);
if (rest_selec != NULL)
*rest_selec = 1.0;
pfree(patt);
pfree(match);
return Pattern_Prefix_Exact; /* pattern specifies exact match */
}
*prefix_const = string_to_const(match, typeid);
*prefix_const = string_to_const(prefix, typeid);
if (rest_selec != NULL)
*rest_selec = regex_selectivity(rest, strlen(rest),
case_insensitive);
{
if (exact)
{
/* Exact match, so there's no additional selectivity */
*rest_selec = 1.0;
}
else
{
char *patt = TextDatumGetCString(patt_const->constvalue);
pfree(patt);
pfree(match);
*rest_selec = regex_selectivity(patt, strlen(patt),
case_insensitive,
strlen(prefix));
pfree(patt);
}
}
if (match_pos > 0)
pfree(prefix);
if (exact)
return Pattern_Prefix_Exact; /* pattern specifies exact match */
else
return Pattern_Prefix_Partial;
return Pattern_Prefix_None;
}
Pattern_Prefix_Status
@ -5387,7 +5265,8 @@ regex_selectivity_sub(const char *patt, int pattlen, bool case_insensitive)
}
static Selectivity
regex_selectivity(const char *patt, int pattlen, bool case_insensitive)
regex_selectivity(const char *patt, int pattlen, bool case_insensitive,
int fixed_prefix_len)
{
Selectivity sel;
@ -5403,9 +5282,14 @@ regex_selectivity(const char *patt, int pattlen, bool case_insensitive)
/* no trailing $ */
sel = regex_selectivity_sub(patt, pattlen, case_insensitive);
sel *= FULL_WILDCARD_SEL;
if (sel > 1.0)
sel = 1.0;
}
/* If there's a fixed prefix, discount its selectivity */
if (fixed_prefix_len > 0)
sel /= pow(FIXED_CHAR_SEL, fixed_prefix_len);
/* Make sure result stays in range */
CLAMP_PROBABILITY(sel);
return sel;
}