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This works by extracting trigrams from the given regular expression, in generally the same spirit as the previously-existing support for LIKE searches, though of course the details are far more complicated. Currently, only GIN indexes are supported. We might be able to make it work with GiST indexes later. The implementation includes adding API functions to backend/regex/ to provide a view of the search NFA created from a regular expression. These functions are meant to be generic enough to be supportable in a standalone version of the regex library, should that ever happen. Alexander Korotkov, reviewed by Heikki Linnakangas and Tom Lane
243 lines
5.6 KiB
C
243 lines
5.6 KiB
C
/*
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* contrib/pg_trgm/trgm_gin.c
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*/
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#include "postgres.h"
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#include "trgm.h"
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#include "access/gin.h"
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#include "access/skey.h"
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PG_FUNCTION_INFO_V1(gin_extract_trgm);
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Datum gin_extract_trgm(PG_FUNCTION_ARGS);
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PG_FUNCTION_INFO_V1(gin_extract_value_trgm);
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Datum gin_extract_value_trgm(PG_FUNCTION_ARGS);
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PG_FUNCTION_INFO_V1(gin_extract_query_trgm);
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Datum gin_extract_query_trgm(PG_FUNCTION_ARGS);
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PG_FUNCTION_INFO_V1(gin_trgm_consistent);
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Datum gin_trgm_consistent(PG_FUNCTION_ARGS);
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/*
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* This function can only be called if a pre-9.1 version of the GIN operator
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* class definition is present in the catalogs (probably as a consequence
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* of upgrade-in-place). Cope.
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*/
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Datum
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gin_extract_trgm(PG_FUNCTION_ARGS)
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{
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if (PG_NARGS() == 3)
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return gin_extract_value_trgm(fcinfo);
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if (PG_NARGS() == 7)
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return gin_extract_query_trgm(fcinfo);
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elog(ERROR, "unexpected number of arguments to gin_extract_trgm");
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PG_RETURN_NULL();
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}
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Datum
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gin_extract_value_trgm(PG_FUNCTION_ARGS)
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{
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text *val = (text *) PG_GETARG_TEXT_P(0);
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int32 *nentries = (int32 *) PG_GETARG_POINTER(1);
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Datum *entries = NULL;
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TRGM *trg;
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int32 trglen;
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*nentries = 0;
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trg = generate_trgm(VARDATA(val), VARSIZE(val) - VARHDRSZ);
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trglen = ARRNELEM(trg);
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if (trglen > 0)
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{
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trgm *ptr;
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int32 i;
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*nentries = trglen;
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entries = (Datum *) palloc(sizeof(Datum) * trglen);
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ptr = GETARR(trg);
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for (i = 0; i < trglen; i++)
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{
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int32 item = trgm2int(ptr);
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entries[i] = Int32GetDatum(item);
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ptr++;
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}
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}
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PG_RETURN_POINTER(entries);
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}
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Datum
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gin_extract_query_trgm(PG_FUNCTION_ARGS)
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{
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text *val = (text *) PG_GETARG_TEXT_P(0);
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int32 *nentries = (int32 *) PG_GETARG_POINTER(1);
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StrategyNumber strategy = PG_GETARG_UINT16(2);
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/* bool **pmatch = (bool **) PG_GETARG_POINTER(3); */
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Pointer **extra_data = (Pointer **) PG_GETARG_POINTER(4);
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/* bool **nullFlags = (bool **) PG_GETARG_POINTER(5); */
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int32 *searchMode = (int32 *) PG_GETARG_POINTER(6);
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Datum *entries = NULL;
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TRGM *trg;
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int32 trglen;
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trgm *ptr;
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TrgmPackedGraph *graph;
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int32 i;
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switch (strategy)
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{
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case SimilarityStrategyNumber:
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trg = generate_trgm(VARDATA(val), VARSIZE(val) - VARHDRSZ);
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break;
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case ILikeStrategyNumber:
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#ifndef IGNORECASE
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elog(ERROR, "cannot handle ~~* with case-sensitive trigrams");
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#endif
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/* FALL THRU */
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case LikeStrategyNumber:
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/*
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* For wildcard search we extract all the trigrams that every
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* potentially-matching string must include.
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*/
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trg = generate_wildcard_trgm(VARDATA(val), VARSIZE(val) - VARHDRSZ);
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break;
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case RegExpICaseStrategyNumber:
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#ifndef IGNORECASE
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elog(ERROR, "cannot handle ~* with case-sensitive trigrams");
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#endif
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/* FALL THRU */
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case RegExpStrategyNumber:
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trg = createTrgmNFA(val, &graph, PG_GET_COLLATION());
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if (trg && ARRNELEM(trg) > 0)
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{
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/*
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* Successful regex processing: store NFA-like graph as
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* extra_data. GIN API requires an array of nentries
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* Pointers, but we just put the same value in each element.
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*/
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trglen = ARRNELEM(trg);
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*extra_data = (Pointer *) palloc(sizeof(Pointer) * trglen);
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for (i = 0; i < trglen; i++)
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(*extra_data)[i] = (Pointer) graph;
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}
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else
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{
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/* No result: have to do full index scan. */
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*nentries = 0;
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*searchMode = GIN_SEARCH_MODE_ALL;
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PG_RETURN_POINTER(entries);
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}
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break;
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default:
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elog(ERROR, "unrecognized strategy number: %d", strategy);
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trg = NULL; /* keep compiler quiet */
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break;
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}
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trglen = ARRNELEM(trg);
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*nentries = trglen;
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if (trglen > 0)
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{
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entries = (Datum *) palloc(sizeof(Datum) * trglen);
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ptr = GETARR(trg);
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for (i = 0; i < trglen; i++)
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{
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int32 item = trgm2int(ptr);
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entries[i] = Int32GetDatum(item);
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ptr++;
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}
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}
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/*
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* If no trigram was extracted then we have to scan all the index.
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*/
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if (trglen == 0)
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*searchMode = GIN_SEARCH_MODE_ALL;
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PG_RETURN_POINTER(entries);
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}
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Datum
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gin_trgm_consistent(PG_FUNCTION_ARGS)
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{
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bool *check = (bool *) PG_GETARG_POINTER(0);
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StrategyNumber strategy = PG_GETARG_UINT16(1);
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/* text *query = PG_GETARG_TEXT_P(2); */
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int32 nkeys = PG_GETARG_INT32(3);
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Pointer *extra_data = (Pointer *) PG_GETARG_POINTER(4);
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bool *recheck = (bool *) PG_GETARG_POINTER(5);
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bool res;
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int32 i,
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ntrue;
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/* All cases served by this function are inexact */
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*recheck = true;
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switch (strategy)
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{
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case SimilarityStrategyNumber:
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/* Count the matches */
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ntrue = 0;
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for (i = 0; i < nkeys; i++)
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{
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if (check[i])
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ntrue++;
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}
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#ifdef DIVUNION
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res = (nkeys == ntrue) ? true : ((((((float4) ntrue) / ((float4) (nkeys - ntrue)))) >= trgm_limit) ? true : false);
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#else
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res = (nkeys == 0) ? false : ((((((float4) ntrue) / ((float4) nkeys))) >= trgm_limit) ? true : false);
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#endif
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break;
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case ILikeStrategyNumber:
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#ifndef IGNORECASE
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elog(ERROR, "cannot handle ~~* with case-sensitive trigrams");
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#endif
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/* FALL THRU */
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case LikeStrategyNumber:
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/* Check if all extracted trigrams are presented. */
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res = true;
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for (i = 0; i < nkeys; i++)
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{
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if (!check[i])
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{
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res = false;
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break;
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}
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}
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break;
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case RegExpICaseStrategyNumber:
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#ifndef IGNORECASE
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elog(ERROR, "cannot handle ~* with case-sensitive trigrams");
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#endif
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/* FALL THRU */
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case RegExpStrategyNumber:
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if (nkeys < 1)
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{
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/* Regex processing gave no result: do full index scan */
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res = true;
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}
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else
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res = trigramsMatchGraph((TrgmPackedGraph *) extra_data[0],
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check);
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break;
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default:
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elog(ERROR, "unrecognized strategy number: %d", strategy);
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res = false; /* keep compiler quiet */
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break;
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}
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PG_RETURN_BOOL(res);
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}
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