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https://github.com/postgres/postgres.git
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375 lines
6.7 KiB
C
375 lines
6.7 KiB
C
/*
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* $PostgreSQL: pgsql/contrib/pg_trgm/trgm_op.c,v 1.12 2009/06/11 14:48:51 momjian Exp $
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*/
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#include "trgm.h"
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#include <ctype.h>
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#include "utils/array.h"
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#include "catalog/pg_type.h"
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#include "tsearch/ts_locale.h"
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PG_MODULE_MAGIC;
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float4 trgm_limit = 0.3f;
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PG_FUNCTION_INFO_V1(set_limit);
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Datum set_limit(PG_FUNCTION_ARGS);
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Datum
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set_limit(PG_FUNCTION_ARGS)
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{
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float4 nlimit = PG_GETARG_FLOAT4(0);
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if (nlimit < 0 || nlimit > 1.0)
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elog(ERROR, "wrong limit, should be between 0 and 1");
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trgm_limit = nlimit;
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PG_RETURN_FLOAT4(trgm_limit);
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}
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PG_FUNCTION_INFO_V1(show_limit);
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Datum show_limit(PG_FUNCTION_ARGS);
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Datum
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show_limit(PG_FUNCTION_ARGS)
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{
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PG_RETURN_FLOAT4(trgm_limit);
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}
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static int
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comp_trgm(const void *a, const void *b)
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{
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return CMPTRGM(a, b);
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}
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static int
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unique_array(trgm *a, int len)
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{
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trgm *curend,
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*tmp;
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curend = tmp = a;
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while (tmp - a < len)
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if (CMPTRGM(tmp, curend))
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{
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curend++;
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CPTRGM(curend, tmp);
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tmp++;
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}
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else
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tmp++;
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return curend + 1 - a;
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}
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#ifdef KEEPONLYALNUM
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#define iswordchr(c) (t_isalpha(c) || t_isdigit(c))
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#else
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#define iswordchr(c) (!t_isspace(c))
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#endif
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/*
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* Finds first word in string, returns pointer to the word,
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* endword points to the character after word
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*/
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static char *
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find_word(char *str, int lenstr, char **endword, int *charlen)
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{
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char *beginword = str;
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while (beginword - str < lenstr && !iswordchr(beginword))
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beginword += pg_mblen(beginword);
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if (beginword - str >= lenstr)
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return NULL;
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*endword = beginword;
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*charlen = 0;
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while (*endword - str < lenstr && iswordchr(*endword))
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{
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*endword += pg_mblen(*endword);
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(*charlen)++;
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}
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return beginword;
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}
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#ifdef USE_WIDE_UPPER_LOWER
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static void
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cnt_trigram(trgm *tptr, char *str, int bytelen)
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{
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if (bytelen == 3)
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{
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CPTRGM(tptr, str);
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}
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else
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{
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pg_crc32 crc;
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INIT_CRC32(crc);
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COMP_CRC32(crc, str, bytelen);
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FIN_CRC32(crc);
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/*
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* use only 3 upper bytes from crc, hope, it's good enough hashing
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*/
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CPTRGM(tptr, &crc);
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}
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}
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#endif
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/*
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* Adds trigramm from words (already padded).
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*/
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static trgm *
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make_trigrams(trgm *tptr, char *str, int bytelen, int charlen)
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{
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char *ptr = str;
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if (charlen < 3)
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return tptr;
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#ifdef USE_WIDE_UPPER_LOWER
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if (pg_database_encoding_max_length() > 1)
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{
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int lenfirst = pg_mblen(str),
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lenmiddle = pg_mblen(str + lenfirst),
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lenlast = pg_mblen(str + lenfirst + lenmiddle);
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while ((ptr - str) + lenfirst + lenmiddle + lenlast <= bytelen)
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{
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cnt_trigram(tptr, ptr, lenfirst + lenmiddle + lenlast);
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ptr += lenfirst;
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tptr++;
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lenfirst = lenmiddle;
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lenmiddle = lenlast;
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lenlast = pg_mblen(ptr + lenfirst + lenmiddle);
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}
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}
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else
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#endif
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{
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Assert(bytelen == charlen);
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while (ptr - str < bytelen - 2 /* number of trigrams = strlen - 2 */ )
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{
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CPTRGM(tptr, ptr);
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ptr++;
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tptr++;
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}
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}
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return tptr;
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}
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TRGM *
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generate_trgm(char *str, int slen)
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{
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TRGM *trg;
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char *buf;
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trgm *tptr;
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int len,
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charlen,
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bytelen;
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char *bword,
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*eword;
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trg = (TRGM *) palloc(TRGMHDRSIZE + sizeof(trgm) * (slen / 2 + 1) *3);
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trg->flag = ARRKEY;
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SET_VARSIZE(trg, TRGMHDRSIZE);
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if (slen + LPADDING + RPADDING < 3 || slen == 0)
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return trg;
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tptr = GETARR(trg);
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buf = palloc(sizeof(char) * (slen + 4));
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if (LPADDING > 0)
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{
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*buf = ' ';
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if (LPADDING > 1)
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*(buf + 1) = ' ';
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}
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eword = str;
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while ((bword = find_word(eword, slen - (eword - str), &eword, &charlen)) != NULL)
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{
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#ifdef IGNORECASE
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bword = lowerstr_with_len(bword, eword - bword);
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bytelen = strlen(bword);
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#else
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bytelen = eword - bword;
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#endif
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memcpy(buf + LPADDING, bword, bytelen);
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#ifdef IGNORECASE
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pfree(bword);
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#endif
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buf[LPADDING + bytelen] = ' ';
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buf[LPADDING + bytelen + 1] = ' ';
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/*
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* count trigrams
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*/
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tptr = make_trigrams(tptr, buf, bytelen + LPADDING + RPADDING,
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charlen + LPADDING + RPADDING);
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}
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pfree(buf);
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if ((len = tptr - GETARR(trg)) == 0)
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return trg;
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if (len > 0)
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{
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qsort((void *) GETARR(trg), len, sizeof(trgm), comp_trgm);
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len = unique_array(GETARR(trg), len);
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}
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SET_VARSIZE(trg, CALCGTSIZE(ARRKEY, len));
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return trg;
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}
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uint32
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trgm2int(trgm *ptr)
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{
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uint32 val = 0;
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val |= *(((unsigned char *) ptr));
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val <<= 8;
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val |= *(((unsigned char *) ptr) + 1);
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val <<= 8;
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val |= *(((unsigned char *) ptr) + 2);
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return val;
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}
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PG_FUNCTION_INFO_V1(show_trgm);
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Datum show_trgm(PG_FUNCTION_ARGS);
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Datum
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show_trgm(PG_FUNCTION_ARGS)
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{
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text *in = PG_GETARG_TEXT_P(0);
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TRGM *trg;
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Datum *d;
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ArrayType *a;
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trgm *ptr;
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int i;
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trg = generate_trgm(VARDATA(in), VARSIZE(in) - VARHDRSZ);
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d = (Datum *) palloc(sizeof(Datum) * (1 + ARRNELEM(trg)));
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for (i = 0, ptr = GETARR(trg); i < ARRNELEM(trg); i++, ptr++)
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{
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text *item = (text *) palloc(VARHDRSZ + Max(12, pg_database_encoding_max_length() * 3));
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if (pg_database_encoding_max_length() > 1 && !ISPRINTABLETRGM(ptr))
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{
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snprintf(VARDATA(item), 12, "0x%06x", trgm2int(ptr));
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SET_VARSIZE(item, VARHDRSZ + strlen(VARDATA(item)));
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}
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else
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{
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SET_VARSIZE(item, VARHDRSZ + 3);
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CPTRGM(VARDATA(item), ptr);
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}
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d[i] = PointerGetDatum(item);
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}
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a = construct_array(
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d,
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ARRNELEM(trg),
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TEXTOID,
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-1,
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false,
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'i'
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);
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for (i = 0; i < ARRNELEM(trg); i++)
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pfree(DatumGetPointer(d[i]));
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pfree(d);
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pfree(trg);
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PG_FREE_IF_COPY(in, 0);
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PG_RETURN_POINTER(a);
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}
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float4
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cnt_sml(TRGM *trg1, TRGM *trg2)
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{
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trgm *ptr1,
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*ptr2;
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int count = 0;
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int len1,
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len2;
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ptr1 = GETARR(trg1);
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ptr2 = GETARR(trg2);
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len1 = ARRNELEM(trg1);
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len2 = ARRNELEM(trg2);
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while (ptr1 - GETARR(trg1) < len1 && ptr2 - GETARR(trg2) < len2)
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{
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int res = CMPTRGM(ptr1, ptr2);
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if (res < 0)
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ptr1++;
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else if (res > 0)
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ptr2++;
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else
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{
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ptr1++;
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ptr2++;
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count++;
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}
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}
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#ifdef DIVUNION
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return ((((float4) count) / ((float4) (len1 + len2 - count))));
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#else
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return (((float) count) / ((float) ((len1 > len2) ? len1 : len2)));
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#endif
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}
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PG_FUNCTION_INFO_V1(similarity);
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Datum similarity(PG_FUNCTION_ARGS);
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Datum
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similarity(PG_FUNCTION_ARGS)
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{
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text *in1 = PG_GETARG_TEXT_P(0);
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text *in2 = PG_GETARG_TEXT_P(1);
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TRGM *trg1,
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*trg2;
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float4 res;
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trg1 = generate_trgm(VARDATA(in1), VARSIZE(in1) - VARHDRSZ);
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trg2 = generate_trgm(VARDATA(in2), VARSIZE(in2) - VARHDRSZ);
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res = cnt_sml(trg1, trg2);
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pfree(trg1);
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pfree(trg2);
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PG_FREE_IF_COPY(in1, 0);
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PG_FREE_IF_COPY(in2, 1);
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PG_RETURN_FLOAT4(res);
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}
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PG_FUNCTION_INFO_V1(similarity_op);
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Datum similarity_op(PG_FUNCTION_ARGS);
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Datum
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similarity_op(PG_FUNCTION_ARGS)
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{
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float4 res = DatumGetFloat4(DirectFunctionCall2(
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similarity,
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PG_GETARG_DATUM(0),
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PG_GETARG_DATUM(1)
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));
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PG_RETURN_BOOL(res >= trgm_limit);
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}
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