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postgresql/contrib/pg_trgm/trgm_op.c

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/*
* contrib/pg_trgm/trgm_op.c
*/
#include "postgres.h"
#include <ctype.h>
#include "trgm.h"
#include "catalog/pg_type.h"
#include "tsearch/ts_locale.h"
PG_MODULE_MAGIC;
float4 trgm_limit = 0.3f;
PG_FUNCTION_INFO_V1(set_limit);
Datum set_limit(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(show_limit);
Datum show_limit(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(show_trgm);
Datum show_trgm(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(similarity);
Datum similarity(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(similarity_dist);
Datum similarity_dist(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(similarity_op);
Datum similarity_op(PG_FUNCTION_ARGS);
Datum
set_limit(PG_FUNCTION_ARGS)
{
float4 nlimit = PG_GETARG_FLOAT4(0);
if (nlimit < 0 || nlimit > 1.0)
elog(ERROR, "wrong limit, should be between 0 and 1");
trgm_limit = nlimit;
PG_RETURN_FLOAT4(trgm_limit);
}
Datum
show_limit(PG_FUNCTION_ARGS)
{
PG_RETURN_FLOAT4(trgm_limit);
}
static int
comp_trgm(const void *a, const void *b)
{
return CMPTRGM(a, b);
}
static int
unique_array(trgm *a, int len)
{
trgm *curend,
*tmp;
curend = tmp = a;
while (tmp - a < len)
if (CMPTRGM(tmp, curend))
{
curend++;
CPTRGM(curend, tmp);
tmp++;
}
else
tmp++;
return curend + 1 - a;
}
/*
* Finds first word in string, returns pointer to the word,
* endword points to the character after word
*/
static char *
find_word(char *str, int lenstr, char **endword, int *charlen)
{
char *beginword = str;
while (beginword - str < lenstr && !ISWORDCHR(beginword))
beginword += pg_mblen(beginword);
if (beginword - str >= lenstr)
return NULL;
*endword = beginword;
*charlen = 0;
while (*endword - str < lenstr && ISWORDCHR(*endword))
{
*endword += pg_mblen(*endword);
(*charlen)++;
}
return beginword;
}
/*
* Reduce a trigram (three possibly multi-byte characters) to a trgm,
* which is always exactly three bytes. If we have three single-byte
* characters, we just use them as-is; otherwise we form a hash value.
*/
void
compact_trigram(trgm *tptr, char *str, int bytelen)
{
if (bytelen == 3)
{
CPTRGM(tptr, str);
}
else
{
pg_crc32 crc;
INIT_CRC32(crc);
COMP_CRC32(crc, str, bytelen);
FIN_CRC32(crc);
/*
* use only 3 upper bytes from crc, hope, it's good enough hashing
*/
CPTRGM(tptr, &crc);
}
}
/*
* Adds trigrams from words (already padded).
*/
static trgm *
make_trigrams(trgm *tptr, char *str, int bytelen, int charlen)
{
char *ptr = str;
if (charlen < 3)
return tptr;
if (bytelen > charlen)
{
/* Find multibyte character boundaries and apply compact_trigram */
int lenfirst = pg_mblen(str),
lenmiddle = pg_mblen(str + lenfirst),
lenlast = pg_mblen(str + lenfirst + lenmiddle);
while ((ptr - str) + lenfirst + lenmiddle + lenlast <= bytelen)
{
compact_trigram(tptr, ptr, lenfirst + lenmiddle + lenlast);
ptr += lenfirst;
tptr++;
lenfirst = lenmiddle;
lenmiddle = lenlast;
lenlast = pg_mblen(ptr + lenfirst + lenmiddle);
}
}
else
{
/* Fast path when there are no multibyte characters */
Assert(bytelen == charlen);
while (ptr - str < bytelen - 2 /* number of trigrams = strlen - 2 */ )
{
CPTRGM(tptr, ptr);
ptr++;
tptr++;
}
}
return tptr;
}
TRGM *
generate_trgm(char *str, int slen)
{
TRGM *trg;
char *buf;
trgm *tptr;
int len,
charlen,
bytelen;
char *bword,
*eword;
trg = (TRGM *) palloc(TRGMHDRSIZE + sizeof(trgm) * (slen / 2 + 1) *3);
trg->flag = ARRKEY;
SET_VARSIZE(trg, TRGMHDRSIZE);
if (slen + LPADDING + RPADDING < 3 || slen == 0)
return trg;
tptr = GETARR(trg);
buf = palloc(sizeof(char) * (slen + 4));
if (LPADDING > 0)
{
*buf = ' ';
if (LPADDING > 1)
*(buf + 1) = ' ';
}
eword = str;
while ((bword = find_word(eword, slen - (eword - str), &eword, &charlen)) != NULL)
{
#ifdef IGNORECASE
bword = lowerstr_with_len(bword, eword - bword);
bytelen = strlen(bword);
#else
bytelen = eword - bword;
#endif
memcpy(buf + LPADDING, bword, bytelen);
#ifdef IGNORECASE
pfree(bword);
#endif
buf[LPADDING + bytelen] = ' ';
buf[LPADDING + bytelen + 1] = ' ';
/*
* count trigrams
*/
tptr = make_trigrams(tptr, buf, bytelen + LPADDING + RPADDING,
charlen + LPADDING + RPADDING);
}
pfree(buf);
if ((len = tptr - GETARR(trg)) == 0)
return trg;
if (len > 0)
{
qsort((void *) GETARR(trg), len, sizeof(trgm), comp_trgm);
len = unique_array(GETARR(trg), len);
}
SET_VARSIZE(trg, CALCGTSIZE(ARRKEY, len));
return trg;
}
/*
* Extract the next non-wildcard part of a search string, ie, a word bounded
* by '_' or '%' meta-characters, non-word characters or string end.
*
* str: source string, of length lenstr bytes (need not be null-terminated)
* buf: where to return the substring (must be long enough)
* *bytelen: receives byte length of the found substring
* *charlen: receives character length of the found substring
*
* Returns pointer to end+1 of the found substring in the source string.
* Returns NULL if no word found (in which case buf, bytelen, charlen not set)
*
* If the found word is bounded by non-word characters or string boundaries
* then this function will include corresponding padding spaces into buf.
*/
static const char *
get_wildcard_part(const char *str, int lenstr,
char *buf, int *bytelen, int *charlen)
{
const char *beginword = str;
const char *endword;
char *s = buf;
bool in_leading_wildcard_meta = false;
bool in_trailing_wildcard_meta = false;
bool in_escape = false;
int clen;
/*
* Find the first word character, remembering whether preceding character
* was wildcard meta-character. Note that the in_escape state persists
* from this loop to the next one, since we may exit at a word character
* that is in_escape.
*/
while (beginword - str < lenstr)
{
if (in_escape)
{
if (ISWORDCHR(beginword))
break;
in_escape = false;
in_leading_wildcard_meta = false;
}
else
{
if (ISESCAPECHAR(beginword))
in_escape = true;
else if (ISWILDCARDCHAR(beginword))
in_leading_wildcard_meta = true;
else if (ISWORDCHR(beginword))
break;
else
in_leading_wildcard_meta = false;
}
beginword += pg_mblen(beginword);
}
/*
* Handle string end.
*/
if (beginword - str >= lenstr)
return NULL;
/*
* Add left padding spaces if preceding character wasn't wildcard
* meta-character.
*/
*charlen = 0;
if (!in_leading_wildcard_meta)
{
if (LPADDING > 0)
{
*s++ = ' ';
(*charlen)++;
if (LPADDING > 1)
{
*s++ = ' ';
(*charlen)++;
}
}
}
/*
* Copy data into buf until wildcard meta-character, non-word character or
* string boundary. Strip escapes during copy.
*/
endword = beginword;
while (endword - str < lenstr)
{
clen = pg_mblen(endword);
if (in_escape)
{
if (ISWORDCHR(endword))
{
memcpy(s, endword, clen);
(*charlen)++;
s += clen;
}
else
{
/*
* Back up endword to the escape character when stopping at
* an escaped char, so that subsequent get_wildcard_part will
* restart from the escape character. We assume here that
* escape chars are single-byte.
*/
endword--;
break;
}
in_escape = false;
}
else
{
if (ISESCAPECHAR(endword))
in_escape = true;
else if (ISWILDCARDCHAR(endword))
{
in_trailing_wildcard_meta = true;
break;
}
else if (ISWORDCHR(endword))
{
memcpy(s, endword, clen);
(*charlen)++;
s += clen;
}
else
break;
}
endword += clen;
}
/*
* Add right padding spaces if next character isn't wildcard
* meta-character.
*/
if (!in_trailing_wildcard_meta)
{
if (RPADDING > 0)
{
*s++ = ' ';
(*charlen)++;
if (RPADDING > 1)
{
*s++ = ' ';
(*charlen)++;
}
}
}
*bytelen = s - buf;
return endword;
}
/*
* Generates trigrams for wildcard search string.
*
* Returns array of trigrams that must occur in any string that matches the
* wildcard string. For example, given pattern "a%bcd%" the trigrams
* " a", "bcd" would be extracted.
*/
TRGM *
generate_wildcard_trgm(const char *str, int slen)
{
TRGM *trg;
char *buf,
*buf2;
trgm *tptr;
int len,
charlen,
bytelen;
const char *eword;
trg = (TRGM *) palloc(TRGMHDRSIZE + sizeof(trgm) * (slen / 2 + 1) *3);
trg->flag = ARRKEY;
SET_VARSIZE(trg, TRGMHDRSIZE);
if (slen + LPADDING + RPADDING < 3 || slen == 0)
return trg;
tptr = GETARR(trg);
buf = palloc(sizeof(char) * (slen + 4));
/*
* Extract trigrams from each substring extracted by get_wildcard_part.
*/
eword = str;
while ((eword = get_wildcard_part(eword, slen - (eword - str),
buf, &bytelen, &charlen)) != NULL)
{
#ifdef IGNORECASE
buf2 = lowerstr_with_len(buf, bytelen);
bytelen = strlen(buf2);
#else
buf2 = buf;
#endif
/*
* count trigrams
*/
tptr = make_trigrams(tptr, buf2, bytelen, charlen);
#ifdef IGNORECASE
pfree(buf2);
#endif
}
pfree(buf);
if ((len = tptr - GETARR(trg)) == 0)
return trg;
/*
* Make trigrams unique.
*/
if (len > 0)
{
qsort((void *) GETARR(trg), len, sizeof(trgm), comp_trgm);
len = unique_array(GETARR(trg), len);
}
SET_VARSIZE(trg, CALCGTSIZE(ARRKEY, len));
return trg;
}
uint32
trgm2int(trgm *ptr)
{
uint32 val = 0;
val |= *(((unsigned char *) ptr));
val <<= 8;
val |= *(((unsigned char *) ptr) + 1);
val <<= 8;
val |= *(((unsigned char *) ptr) + 2);
return val;
}
Datum
show_trgm(PG_FUNCTION_ARGS)
{
text *in = PG_GETARG_TEXT_P(0);
TRGM *trg;
Datum *d;
ArrayType *a;
trgm *ptr;
int i;
trg = generate_trgm(VARDATA(in), VARSIZE(in) - VARHDRSZ);
d = (Datum *) palloc(sizeof(Datum) * (1 + ARRNELEM(trg)));
for (i = 0, ptr = GETARR(trg); i < ARRNELEM(trg); i++, ptr++)
{
text *item = (text *) palloc(VARHDRSZ + Max(12, pg_database_encoding_max_length() * 3));
if (pg_database_encoding_max_length() > 1 && !ISPRINTABLETRGM(ptr))
{
snprintf(VARDATA(item), 12, "0x%06x", trgm2int(ptr));
SET_VARSIZE(item, VARHDRSZ + strlen(VARDATA(item)));
}
else
{
SET_VARSIZE(item, VARHDRSZ + 3);
CPTRGM(VARDATA(item), ptr);
}
d[i] = PointerGetDatum(item);
}
a = construct_array(
d,
ARRNELEM(trg),
TEXTOID,
-1,
false,
'i'
);
for (i = 0; i < ARRNELEM(trg); i++)
pfree(DatumGetPointer(d[i]));
pfree(d);
pfree(trg);
PG_FREE_IF_COPY(in, 0);
PG_RETURN_POINTER(a);
}
float4
cnt_sml(TRGM *trg1, TRGM *trg2)
{
trgm *ptr1,
*ptr2;
int count = 0;
int len1,
len2;
ptr1 = GETARR(trg1);
ptr2 = GETARR(trg2);
len1 = ARRNELEM(trg1);
len2 = ARRNELEM(trg2);
/* explicit test is needed to avoid 0/0 division when both lengths are 0 */
if (len1 <= 0 || len2 <= 0)
return (float4) 0.0;
while (ptr1 - GETARR(trg1) < len1 && ptr2 - GETARR(trg2) < len2)
{
int res = CMPTRGM(ptr1, ptr2);
if (res < 0)
ptr1++;
else if (res > 0)
ptr2++;
else
{
ptr1++;
ptr2++;
count++;
}
}
#ifdef DIVUNION
return ((float4) count) / ((float4) (len1 + len2 - count));
#else
return ((float4) count) / ((float4) ((len1 > len2) ? len1 : len2));
#endif
}
/*
* Returns whether trg2 contains all trigrams in trg1.
* This relies on the trigram arrays being sorted.
*/
bool
trgm_contained_by(TRGM *trg1, TRGM *trg2)
{
trgm *ptr1,
*ptr2;
int len1,
len2;
ptr1 = GETARR(trg1);
ptr2 = GETARR(trg2);
len1 = ARRNELEM(trg1);
len2 = ARRNELEM(trg2);
while (ptr1 - GETARR(trg1) < len1 && ptr2 - GETARR(trg2) < len2)
{
int res = CMPTRGM(ptr1, ptr2);
if (res < 0)
return false;
else if (res > 0)
ptr2++;
else
{
ptr1++;
ptr2++;
}
}
if (ptr1 - GETARR(trg1) < len1)
return false;
else
return true;
}
/*
* Return a palloc'd boolean array showing, for each trigram in "query",
* whether it is present in the trigram array "key".
* This relies on the "key" array being sorted, but "query" need not be.
*/
bool *
trgm_presence_map(TRGM *query, TRGM *key)
{
bool *result;
trgm *ptrq = GETARR(query),
*ptrk = GETARR(key);
int lenq = ARRNELEM(query),
lenk = ARRNELEM(key),
i;
result = (bool *) palloc0(lenq * sizeof(bool));
/* for each query trigram, do a binary search in the key array */
for (i = 0; i < lenq; i++)
{
int lo = 0;
int hi = lenk;
while (lo < hi)
{
int mid = (lo + hi) / 2;
int res = CMPTRGM(ptrq, ptrk + mid);
if (res < 0)
hi = mid;
else if (res > 0)
lo = mid + 1;
else
{
result[i] = true;
break;
}
}
ptrq++;
}
return result;
}
Datum
similarity(PG_FUNCTION_ARGS)
{
text *in1 = PG_GETARG_TEXT_P(0);
text *in2 = PG_GETARG_TEXT_P(1);
TRGM *trg1,
*trg2;
float4 res;
trg1 = generate_trgm(VARDATA(in1), VARSIZE(in1) - VARHDRSZ);
trg2 = generate_trgm(VARDATA(in2), VARSIZE(in2) - VARHDRSZ);
res = cnt_sml(trg1, trg2);
pfree(trg1);
pfree(trg2);
PG_FREE_IF_COPY(in1, 0);
PG_FREE_IF_COPY(in2, 1);
PG_RETURN_FLOAT4(res);
}
Datum
similarity_dist(PG_FUNCTION_ARGS)
{
float4 res = DatumGetFloat4(DirectFunctionCall2(similarity,
PG_GETARG_DATUM(0),
PG_GETARG_DATUM(1)));
PG_RETURN_FLOAT4(1.0 - res);
}
Datum
similarity_op(PG_FUNCTION_ARGS)
{
float4 res = DatumGetFloat4(DirectFunctionCall2(similarity,
PG_GETARG_DATUM(0),
PG_GETARG_DATUM(1)));
PG_RETURN_BOOL(res >= trgm_limit);
}
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