From f576b17cd6ba653bdace1f0da9a3b57f4984e460 Mon Sep 17 00:00:00 2001
From: Teodor Sigaev <teodor@sigaev.ru>
Date: Wed, 16 Mar 2016 18:59:21 +0300
Subject: [PATCH] Add word_similarity to pg_trgm contrib module.
Patch introduces a concept of similarity over string and just a word from
another string.
Version of extension is not changed because 1.2 was already introduced in 9.6
release cycle, so, there wasn't a public version.
Author: Alexander Korotkov, Artur Zakirov
---
contrib/pg_trgm/Makefile | 2 +-
contrib/pg_trgm/expected/pg_trgm.out | 4 +-
contrib/pg_trgm/pg_trgm--1.1--1.2.sql | 64 +++-
contrib/pg_trgm/pg_trgm--1.2.sql | 64 ++++
contrib/pg_trgm/sql/pg_trgm.sql | 4 +-
contrib/pg_trgm/trgm.h | 30 +-
contrib/pg_trgm/trgm_gin.c | 20 +-
contrib/pg_trgm/trgm_gist.c | 33 +-
contrib/pg_trgm/trgm_op.c | 501 +++++++++++++++++++++++---
doc/src/sgml/pgtrgm.sgml | 79 ++++
10 files changed, 726 insertions(+), 75 deletions(-)
diff --git a/contrib/pg_trgm/Makefile b/contrib/pg_trgm/Makefile
index 1e387536221..c0c78f34599 100644
--- a/contrib/pg_trgm/Makefile
+++ b/contrib/pg_trgm/Makefile
@@ -7,7 +7,7 @@ EXTENSION = pg_trgm
DATA = pg_trgm--1.2.sql pg_trgm--1.0--1.1.sql pg_trgm--1.1--1.2.sql pg_trgm--unpackaged--1.0.sql
PGFILEDESC = "pg_trgm - trigram matching"
-REGRESS = pg_trgm
+REGRESS = pg_trgm pg_word_trgm
ifdef USE_PGXS
PG_CONFIG = pg_config
diff --git a/contrib/pg_trgm/expected/pg_trgm.out b/contrib/pg_trgm/expected/pg_trgm.out
index 13b1fde1b8b..78e8174f866 100644
--- a/contrib/pg_trgm/expected/pg_trgm.out
+++ b/contrib/pg_trgm/expected/pg_trgm.out
@@ -59,7 +59,7 @@ select similarity('---', '####---');
0
(1 row)
-CREATE TABLE test_trgm(t text);
+CREATE TABLE test_trgm(t text COLLATE "C");
\copy test_trgm from 'data/trgm.data'
select t,similarity(t,'qwertyu0988') as sml from test_trgm where t % 'qwertyu0988' order by sml desc, t;
t | sml
@@ -3467,7 +3467,7 @@ select t,similarity(t,'gwertyu1988') as sml from test_trgm where t % 'gwertyu198
qwertyu0988 | 0.333333
(1 row)
-create table test2(t text);
+create table test2(t text COLLATE "C");
insert into test2 values ('abcdef');
insert into test2 values ('quark');
insert into test2 values (' z foo bar');
diff --git a/contrib/pg_trgm/pg_trgm--1.1--1.2.sql b/contrib/pg_trgm/pg_trgm--1.1--1.2.sql
index c101f21061b..ff0f13fd08c 100644
--- a/contrib/pg_trgm/pg_trgm--1.1--1.2.sql
+++ b/contrib/pg_trgm/pg_trgm--1.1--1.2.sql
@@ -3,10 +3,72 @@
-- complain if script is sourced in psql, rather than via ALTER EXTENSION
\echo Use "ALTER EXTENSION pg_trgm UPDATE TO '1.2'" to load this file. \quit
+CREATE FUNCTION word_similarity(text,text)
+RETURNS float4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
+CREATE FUNCTION word_similarity_op(text,text)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT STABLE; -- stable because depends on pg_trgm.word_similarity_threshold
+
+CREATE FUNCTION word_similarity_commutator_op(text,text)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT STABLE; -- stable because depends on pg_trgm.word_similarity_threshold
+
+CREATE FUNCTION word_similarity_dist_op(text,text)
+RETURNS float4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
+CREATE FUNCTION word_similarity_dist_commutator_op(text,text)
+RETURNS float4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
+CREATE OPERATOR <% (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_op,
+ COMMUTATOR = '%>',
+ RESTRICT = contsel,
+ JOIN = contjoinsel
+);
+
+CREATE OPERATOR %> (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_commutator_op,
+ COMMUTATOR = '<%',
+ RESTRICT = contsel,
+ JOIN = contjoinsel
+);
+
+CREATE OPERATOR <<-> (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_dist_op,
+ COMMUTATOR = '<->>'
+);
+
+CREATE OPERATOR <->> (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_dist_commutator_op,
+ COMMUTATOR = '<<->'
+);
+
CREATE FUNCTION gin_trgm_triconsistent(internal, int2, text, int4, internal, internal, internal)
RETURNS "char"
AS 'MODULE_PATHNAME'
LANGUAGE C IMMUTABLE STRICT;
+ALTER OPERATOR FAMILY gist_trgm_ops USING gist ADD
+ OPERATOR 7 %> (text, text),
+ OPERATOR 8 <->> (text, text) FOR ORDER BY pg_catalog.float_ops;
+
ALTER OPERATOR FAMILY gin_trgm_ops USING gin ADD
- FUNCTION 6 (text, text) gin_trgm_triconsistent (internal, int2, text, int4, internal, internal, internal);
+ OPERATOR 7 %> (text, text),
+ FUNCTION 6 (text, text) gin_trgm_triconsistent (internal, int2, text, int4, internal, internal, internal);
diff --git a/contrib/pg_trgm/pg_trgm--1.2.sql b/contrib/pg_trgm/pg_trgm--1.2.sql
index 5ee115ecdc1..bc23dfe0f3b 100644
--- a/contrib/pg_trgm/pg_trgm--1.2.sql
+++ b/contrib/pg_trgm/pg_trgm--1.2.sql
@@ -39,6 +39,39 @@ CREATE OPERATOR % (
JOIN = contjoinsel
);
+CREATE FUNCTION word_similarity(text,text)
+RETURNS float4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
+CREATE FUNCTION word_similarity_op(text,text)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT STABLE; -- stable because depends on pg_trgm.word_similarity_threshold
+
+CREATE FUNCTION word_similarity_commutator_op(text,text)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT STABLE; -- stable because depends on pg_trgm.word_similarity_threshold
+
+CREATE OPERATOR <% (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_op,
+ COMMUTATOR = '%>',
+ RESTRICT = contsel,
+ JOIN = contjoinsel
+);
+
+CREATE OPERATOR %> (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_commutator_op,
+ COMMUTATOR = '<%',
+ RESTRICT = contsel,
+ JOIN = contjoinsel
+);
+
CREATE FUNCTION similarity_dist(text,text)
RETURNS float4
AS 'MODULE_PATHNAME'
@@ -51,6 +84,30 @@ CREATE OPERATOR <-> (
COMMUTATOR = '<->'
);
+CREATE FUNCTION word_similarity_dist_op(text,text)
+RETURNS float4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
+CREATE FUNCTION word_similarity_dist_commutator_op(text,text)
+RETURNS float4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT IMMUTABLE;
+
+CREATE OPERATOR <<-> (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_dist_op,
+ COMMUTATOR = '<->>'
+);
+
+CREATE OPERATOR <->> (
+ LEFTARG = text,
+ RIGHTARG = text,
+ PROCEDURE = word_similarity_dist_commutator_op,
+ COMMUTATOR = '<<->'
+);
+
-- gist key
CREATE FUNCTION gtrgm_in(cstring)
RETURNS gtrgm
@@ -140,6 +197,12 @@ ALTER OPERATOR FAMILY gist_trgm_ops USING gist ADD
OPERATOR 5 pg_catalog.~ (text, text),
OPERATOR 6 pg_catalog.~* (text, text);
+-- Add operators that are new in 9.6 (pg_trgm 1.2).
+
+ALTER OPERATOR FAMILY gist_trgm_ops USING gist ADD
+ OPERATOR 7 %> (text, text),
+ OPERATOR 8 <->> (text, text) FOR ORDER BY pg_catalog.float_ops;
+
-- support functions for gin
CREATE FUNCTION gin_extract_value_trgm(text, internal)
RETURNS internal
@@ -187,4 +250,5 @@ AS 'MODULE_PATHNAME'
LANGUAGE C IMMUTABLE STRICT;
ALTER OPERATOR FAMILY gin_trgm_ops USING gin ADD
+ OPERATOR 7 %> (text, text),
FUNCTION 6 (text,text) gin_trgm_triconsistent (internal, int2, text, int4, internal, internal, internal);
diff --git a/contrib/pg_trgm/sql/pg_trgm.sql b/contrib/pg_trgm/sql/pg_trgm.sql
index 7b02d988187..6cefc8e643a 100644
--- a/contrib/pg_trgm/sql/pg_trgm.sql
+++ b/contrib/pg_trgm/sql/pg_trgm.sql
@@ -13,7 +13,7 @@ select similarity('wow',' WOW ');
select similarity('---', '####---');
-CREATE TABLE test_trgm(t text);
+CREATE TABLE test_trgm(t text COLLATE "C");
\copy test_trgm from 'data/trgm.data'
@@ -40,7 +40,7 @@ select t,similarity(t,'qwertyu0988') as sml from test_trgm where t % 'qwertyu098
select t,similarity(t,'gwertyu0988') as sml from test_trgm where t % 'gwertyu0988' order by sml desc, t;
select t,similarity(t,'gwertyu1988') as sml from test_trgm where t % 'gwertyu1988' order by sml desc, t;
-create table test2(t text);
+create table test2(t text COLLATE "C");
insert into test2 values ('abcdef');
insert into test2 values ('quark');
insert into test2 values (' z foo bar');
diff --git a/contrib/pg_trgm/trgm.h b/contrib/pg_trgm/trgm.h
index 046cf58e134..8cd88e763c1 100644
--- a/contrib/pg_trgm/trgm.h
+++ b/contrib/pg_trgm/trgm.h
@@ -26,13 +26,14 @@
#define DIVUNION
/* operator strategy numbers */
-#define SimilarityStrategyNumber 1
-#define DistanceStrategyNumber 2
-#define LikeStrategyNumber 3
-#define ILikeStrategyNumber 4
-#define RegExpStrategyNumber 5
-#define RegExpICaseStrategyNumber 6
-
+#define SimilarityStrategyNumber 1
+#define DistanceStrategyNumber 2
+#define LikeStrategyNumber 3
+#define ILikeStrategyNumber 4
+#define RegExpStrategyNumber 5
+#define RegExpICaseStrategyNumber 6
+#define WordSimilarityStrategyNumber 7
+#define WordDistanceStrategyNumber 8
typedef char trgm[3];
@@ -103,15 +104,28 @@ typedef char *BITVECP;
#define GETARR(x) ( (trgm*)( (char*)x+TRGMHDRSIZE ) )
#define ARRNELEM(x) ( ( VARSIZE(x) - TRGMHDRSIZE )/sizeof(trgm) )
+/*
+ * If DIVUNION is defined then similarity formula is:
+ * count / (len1 + len2 - count)
+ * else if DIVUNION is not defined then similarity formula is:
+ * count / max(len1, len2)
+ */
+#ifdef DIVUNION
+#define CALCSML(count, len1, len2) ((float4) (count)) / ((float4) ((len1) + (len2) - (count)))
+#else
+#define CALCSML(count, len1, len2) ((float4) (count)) / ((float4) (((len1) > (len2)) ? (len1) : (len2)))
+#endif
+
typedef struct TrgmPackedGraph TrgmPackedGraph;
extern double similarity_threshold;
+extern double word_similarity_threshold;
extern uint32 trgm2int(trgm *ptr);
extern void compact_trigram(trgm *tptr, char *str, int bytelen);
extern TRGM *generate_trgm(char *str, int slen);
extern TRGM *generate_wildcard_trgm(const char *str, int slen);
-extern float4 cnt_sml(TRGM *trg1, TRGM *trg2);
+extern float4 cnt_sml(TRGM *trg1, TRGM *trg2, bool inexact);
extern bool trgm_contained_by(TRGM *trg1, TRGM *trg2);
extern bool *trgm_presence_map(TRGM *query, TRGM *key);
extern TRGM *createTrgmNFA(text *text_re, Oid collation,
diff --git a/contrib/pg_trgm/trgm_gin.c b/contrib/pg_trgm/trgm_gin.c
index ea8edef67ac..6805e3e9b20 100644
--- a/contrib/pg_trgm/trgm_gin.c
+++ b/contrib/pg_trgm/trgm_gin.c
@@ -89,6 +89,7 @@ gin_extract_query_trgm(PG_FUNCTION_ARGS)
switch (strategy)
{
case SimilarityStrategyNumber:
+ case WordSimilarityStrategyNumber:
trg = generate_trgm(VARDATA(val), VARSIZE(val) - VARHDRSZ);
break;
case ILikeStrategyNumber:
@@ -176,6 +177,7 @@ gin_trgm_consistent(PG_FUNCTION_ARGS)
bool res;
int32 i,
ntrue;
+ double nlimit;
/* All cases served by this function are inexact */
*recheck = true;
@@ -183,6 +185,10 @@ gin_trgm_consistent(PG_FUNCTION_ARGS)
switch (strategy)
{
case SimilarityStrategyNumber:
+ case WordSimilarityStrategyNumber:
+ nlimit = (strategy == SimilarityStrategyNumber) ?
+ similarity_threshold : word_similarity_threshold;
+
/* Count the matches */
ntrue = 0;
for (i = 0; i < nkeys; i++)
@@ -207,8 +213,7 @@ gin_trgm_consistent(PG_FUNCTION_ARGS)
* So, independly on DIVUNION the upper bound formula is the same.
*/
res = (nkeys == 0) ? false :
- ((((((float4) ntrue) / ((float4) nkeys))) >= similarity_threshold)
- ? true : false);
+ (((((float4) ntrue) / ((float4) nkeys))) >= nlimit);
break;
case ILikeStrategyNumber:
#ifndef IGNORECASE
@@ -270,10 +275,15 @@ gin_trgm_triconsistent(PG_FUNCTION_ARGS)
int32 i,
ntrue;
bool *boolcheck;
+ double nlimit;
switch (strategy)
{
case SimilarityStrategyNumber:
+ case WordSimilarityStrategyNumber:
+ nlimit = (strategy == SimilarityStrategyNumber) ?
+ similarity_threshold : word_similarity_threshold;
+
/* Count the matches */
ntrue = 0;
for (i = 0; i < nkeys; i++)
@@ -285,9 +295,9 @@ gin_trgm_triconsistent(PG_FUNCTION_ARGS)
/*
* See comment in gin_trgm_consistent() about * upper bound formula
*/
- res = (nkeys == 0) ? GIN_FALSE :
- (((((float4) ntrue) / ((float4) nkeys)) >= similarity_threshold)
- ? GIN_MAYBE : GIN_FALSE);
+ res = (nkeys == 0)
+ ? GIN_FALSE : (((((float4) ntrue) / ((float4) nkeys)) >= nlimit)
+ ? GIN_MAYBE : GIN_FALSE);
break;
case ILikeStrategyNumber:
#ifndef IGNORECASE
diff --git a/contrib/pg_trgm/trgm_gist.c b/contrib/pg_trgm/trgm_gist.c
index cbd89586cda..2181c2623fa 100644
--- a/contrib/pg_trgm/trgm_gist.c
+++ b/contrib/pg_trgm/trgm_gist.c
@@ -191,6 +191,7 @@ gtrgm_consistent(PG_FUNCTION_ARGS)
bool res;
Size querysize = VARSIZE(query);
gtrgm_consistent_cache *cache;
+ double nlimit;
/*
* We keep the extracted trigrams in cache, because trigram extraction is
@@ -218,6 +219,7 @@ gtrgm_consistent(PG_FUNCTION_ARGS)
switch (strategy)
{
case SimilarityStrategyNumber:
+ case WordSimilarityStrategyNumber:
qtrg = generate_trgm(VARDATA(query),
querysize - VARHDRSZ);
break;
@@ -286,16 +288,23 @@ gtrgm_consistent(PG_FUNCTION_ARGS)
switch (strategy)
{
case SimilarityStrategyNumber:
- /* Similarity search is exact */
- *recheck = false;
+ case WordSimilarityStrategyNumber:
+ /* Similarity search is exact. Word similarity search is inexact */
+ *recheck = (strategy == WordSimilarityStrategyNumber);
+ nlimit = (strategy == SimilarityStrategyNumber) ?
+ similarity_threshold : word_similarity_threshold;
if (GIST_LEAF(entry))
{ /* all leafs contains orig trgm */
- float4 tmpsml = cnt_sml(key, qtrg);
+ /*
+ * Prevent gcc optimizing the tmpsml variable using volatile
+ * keyword. Otherwise comparison of nlimit and tmpsml may give
+ * wrong results.
+ */
+ float4 volatile tmpsml = cnt_sml(qtrg, key, *recheck);
/* strange bug at freebsd 5.2.1 and gcc 3.3.3 */
- res = (*(int *) &tmpsml == *(int *) &similarity_threshold
- || tmpsml > similarity_threshold) ? true : false;
+ res = (*(int *) &tmpsml == *(int *) &nlimit || tmpsml > nlimit);
}
else if (ISALLTRUE(key))
{ /* non-leaf contains signature */
@@ -309,8 +318,7 @@ gtrgm_consistent(PG_FUNCTION_ARGS)
if (len == 0)
res = false;
else
- res = (((((float8) count) / ((float8) len))) >= similarity_threshold)
- ? true : false;
+ res = (((((float8) count) / ((float8) len))) >= nlimit);
}
break;
case ILikeStrategyNumber:
@@ -428,6 +436,7 @@ gtrgm_distance(PG_FUNCTION_ARGS)
StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);
/* Oid subtype = PG_GETARG_OID(3); */
+ bool *recheck = (bool *) PG_GETARG_POINTER(4);
TRGM *key = (TRGM *) DatumGetPointer(entry->key);
TRGM *qtrg;
float8 res;
@@ -463,9 +472,17 @@ gtrgm_distance(PG_FUNCTION_ARGS)
switch (strategy)
{
case DistanceStrategyNumber:
+ case WordDistanceStrategyNumber:
+ *recheck = strategy == WordDistanceStrategyNumber;
if (GIST_LEAF(entry))
{ /* all leafs contains orig trgm */
- res = 1.0 - cnt_sml(key, qtrg);
+ /*
+ * Prevent gcc optimizing the sml variable using volatile
+ * keyword. Otherwise res can differ from the
+ * word_similarity_dist_op() function.
+ */
+ float4 volatile sml = cnt_sml(qtrg, key, *recheck);
+ res = 1.0 - sml;
}
else if (ISALLTRUE(key))
{ /* all leafs contains orig trgm */
diff --git a/contrib/pg_trgm/trgm_op.c b/contrib/pg_trgm/trgm_op.c
index b2c1f6b0612..eaf20e45159 100644
--- a/contrib/pg_trgm/trgm_op.c
+++ b/contrib/pg_trgm/trgm_op.c
@@ -15,7 +15,8 @@
PG_MODULE_MAGIC;
/* GUC variables */
-double similarity_threshold = 0.3f;
+double similarity_threshold = 0.3f;
+double word_similarity_threshold = 0.6f;
void _PG_init(void);
@@ -23,8 +24,20 @@ PG_FUNCTION_INFO_V1(set_limit);
PG_FUNCTION_INFO_V1(show_limit);
PG_FUNCTION_INFO_V1(show_trgm);
PG_FUNCTION_INFO_V1(similarity);
+PG_FUNCTION_INFO_V1(word_similarity);
PG_FUNCTION_INFO_V1(similarity_dist);
PG_FUNCTION_INFO_V1(similarity_op);
+PG_FUNCTION_INFO_V1(word_similarity_op);
+PG_FUNCTION_INFO_V1(word_similarity_commutator_op);
+PG_FUNCTION_INFO_V1(word_similarity_dist_op);
+PG_FUNCTION_INFO_V1(word_similarity_dist_commutator_op);
+
+/* Trigram with position */
+typedef struct
+{
+ trgm trg;
+ int index;
+} pos_trgm;
/*
* Module load callback
@@ -45,11 +58,23 @@ _PG_init(void)
NULL,
NULL,
NULL);
+ DefineCustomRealVariable("pg_trgm.word_similarity_threshold",
+ "Sets the threshold used by the <%% operator.",
+ "Valid range is 0.0 .. 1.0.",
+ &word_similarity_threshold,
+ 0.6,
+ 0.0,
+ 1.0,
+ PGC_USERSET,
+ 0,
+ NULL,
+ NULL,
+ NULL);
}
/*
* Deprecated function.
- * Use "pg_trgm.similarity_threshold" GUC variable instead of this function
+ * Use "pg_trgm.similarity_threshold" GUC variable instead of this function.
*/
Datum
set_limit(PG_FUNCTION_ARGS)
@@ -59,14 +84,14 @@ set_limit(PG_FUNCTION_ARGS)
if (nlimit < 0 || nlimit > 1.0)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
- errmsg("wrong limit, should be between 0 and 1")));
+ errmsg("wrong threshold, should be between 0 and 1")));
similarity_threshold = nlimit;
PG_RETURN_FLOAT4(similarity_threshold);
}
/*
* Deprecated function.
- * Use "pg_trgm.similarity_threshold" GUC variable instead of this function
+ * Use "pg_trgm.similarity_threshold" GUC variable instead of this function.
*/
Datum
show_limit(PG_FUNCTION_ARGS)
@@ -199,38 +224,28 @@ make_trigrams(trgm *tptr, char *str, int bytelen, int charlen)
return tptr;
}
-TRGM *
-generate_trgm(char *str, int slen)
+/*
+ * Make array of trigrams without sorting and removing duplicate items.
+ *
+ * trg: where to return the array of trigrams.
+ * str: source string, of length slen bytes.
+ *
+ * Returns length of the generated array.
+ */
+static int
+generate_trgm_only(trgm *trg, char *str, int slen)
{
- TRGM *trg;
- char *buf;
trgm *tptr;
- int len,
- charlen,
+ char *buf;
+ int charlen,
bytelen;
char *bword,
*eword;
- /*
- * Guard against possible overflow in the palloc requests below. (We
- * don't worry about the additive constants, since palloc can detect
- * requests that are a little above MaxAllocSize --- we just need to
- * prevent integer overflow in the multiplications.)
- */
- if ((Size) (slen / 2) >= (MaxAllocSize / (sizeof(trgm) * 3)) ||
- (Size) slen >= (MaxAllocSize / pg_database_encoding_max_length()))
- ereport(ERROR,
- (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
- errmsg("out of memory")));
-
- 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;
+ return 0;
- tptr = GETARR(trg);
+ tptr = trg;
/* Allocate a buffer for case-folded, blank-padded words */
buf = (char *) palloc(slen * pg_database_encoding_max_length() + 4);
@@ -270,7 +285,47 @@ generate_trgm(char *str, int slen)
pfree(buf);
- if ((len = tptr - GETARR(trg)) == 0)
+ return tptr - trg;
+}
+
+/*
+ * Guard against possible overflow in the palloc requests below. (We
+ * don't worry about the additive constants, since palloc can detect
+ * requests that are a little above MaxAllocSize --- we just need to
+ * prevent integer overflow in the multiplications.)
+ */
+static void
+protect_out_of_mem(int slen)
+{
+ if ((Size) (slen / 2) >= (MaxAllocSize / (sizeof(trgm) * 3)) ||
+ (Size) slen >= (MaxAllocSize / pg_database_encoding_max_length()))
+ ereport(ERROR,
+ (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+ errmsg("out of memory")));
+}
+
+/*
+ * Make array of trigrams with sorting and removing duplicate items.
+ *
+ * str: source string, of length slen bytes.
+ *
+ * Returns the sorted array of unique trigrams.
+ */
+TRGM *
+generate_trgm(char *str, int slen)
+{
+ TRGM *trg;
+ int len;
+
+ protect_out_of_mem(slen);
+
+ trg = (TRGM *) palloc(TRGMHDRSIZE + sizeof(trgm) * (slen / 2 + 1) *3);
+ trg->flag = ARRKEY;
+
+ len = generate_trgm_only(GETARR(trg), str, slen);
+ SET_VARSIZE(trg, CALCGTSIZE(ARRKEY, len));
+
+ if (len == 0)
return trg;
/*
@@ -287,6 +342,285 @@ generate_trgm(char *str, int slen)
return trg;
}
+/*
+ * Make array of positional trigrams from two trigram arrays trg1 and trg2.
+ *
+ * trg1: trigram array of search pattern, of length len1. trg1 is required
+ * word which positions don't matter and replaced with -1.
+ * trg2: trigram array of text, of length len2. trg2 is haystack where we
+ * search and have to store its positions.
+ *
+ * Returns concatenated trigram array.
+ */
+static pos_trgm *
+make_positional_trgm(trgm *trg1, int len1, trgm *trg2, int len2)
+{
+ pos_trgm *result;
+ int i, len = len1 + len2;
+
+ result = (pos_trgm *) palloc(sizeof(pos_trgm) * len);
+
+ for (i = 0; i < len1; i++)
+ {
+ memcpy(&result[i].trg, &trg1[i], sizeof(trgm));
+ result[i].index = -1;
+ }
+
+ for (i = 0; i < len2; i++)
+ {
+ memcpy(&result[i + len1].trg, &trg2[i], sizeof(trgm));
+ result[i + len1].index = i;
+ }
+
+ return result;
+}
+
+/*
+ * Compare position trigrams: compare trigrams first and position second.
+ */
+static int
+comp_ptrgm(const void *v1, const void *v2)
+{
+ const pos_trgm *p1 = (const pos_trgm *)v1;
+ const pos_trgm *p2 = (const pos_trgm *)v2;
+ int cmp;
+
+ cmp = CMPTRGM(p1->trg, p2->trg);
+ if (cmp != 0)
+ return cmp;
+
+ if (p1->index < p2->index)
+ return -1;
+ else if (p1->index == p2->index)
+ return 0;
+ else
+ return 1;
+}
+
+/*
+ * Iterative search function which calculates maximum similarity with word in
+ * the string. But maximum similarity is calculated only if check_only == false.
+ *
+ * trg2indexes: array which stores indexes of the array "found".
+ * found: array which stores true of false values.
+ * ulen1: count of unique trigrams of array "trg1".
+ * len2: length of array "trg2" and array "trg2indexes".
+ * len: length of the array "found".
+ * check_only: if true then only check existaince of similar search pattern in
+ * text.
+ *
+ * Returns word similarity.
+ */
+static float4
+iterate_word_similarity(int *trg2indexes,
+ bool *found,
+ int ulen1,
+ int len2,
+ int len,
+ bool check_only)
+{
+ int *lastpos,
+ i,
+ ulen2 = 0,
+ count = 0,
+ upper = -1,
+ lower = -1;
+ float4 smlr_cur,
+ smlr_max = 0.0f;
+
+ /* Memorise last position of each trigram */
+ lastpos = (int *) palloc(sizeof(int) * len);
+ memset(lastpos, -1, sizeof(int) * len);
+
+ for (i = 0; i < len2; i++)
+ {
+ /* Get index of next trigram */
+ int trgindex = trg2indexes[i];
+
+ /* Update last position of this trigram */
+ if (lower >= 0 || found[trgindex])
+ {
+ if (lastpos[trgindex] < 0)
+ {
+ ulen2++;
+ if (found[trgindex])
+ count++;
+ }
+ lastpos[trgindex] = i;
+ }
+
+ /* Adjust lower bound if this trigram is present in required substing */
+ if (found[trgindex])
+ {
+ int prev_lower,
+ tmp_ulen2,
+ tmp_lower,
+ tmp_count;
+
+ upper = i;
+ if (lower == -1)
+ {
+ lower = i;
+ ulen2 = 1;
+ }
+
+ smlr_cur = CALCSML(count, ulen1, ulen2);
+
+ /* Also try to adjust upper bound for greater similarity */
+ tmp_count = count;
+ tmp_ulen2 = ulen2;
+ prev_lower = lower;
+ for (tmp_lower = lower; tmp_lower <= upper; tmp_lower++)
+ {
+ float smlr_tmp = CALCSML(tmp_count, ulen1, tmp_ulen2);
+ int tmp_trgindex;
+
+ if (smlr_tmp > smlr_cur)
+ {
+ smlr_cur = smlr_tmp;
+ ulen2 = tmp_ulen2;
+ lower = tmp_lower;
+ count = tmp_count;
+ }
+ /*
+ * if we only check that word similarity is greater than
+ * pg_trgm.word_similarity_threshold we do not need to calculate
+ * a maximum similarity.
+ */
+ if (check_only && smlr_cur >= word_similarity_threshold)
+ break;
+
+ tmp_trgindex = trg2indexes[tmp_lower];
+ if (lastpos[tmp_trgindex] == tmp_lower)
+ {
+ tmp_ulen2--;
+ if (found[tmp_trgindex])
+ tmp_count--;
+ }
+ }
+
+ smlr_max = Max(smlr_max, smlr_cur);
+ /*
+ * if we only check that word similarity is greater than
+ * pg_trgm.word_similarity_threshold we do not need to calculate a
+ * maximum similarity
+ */
+ if (check_only && smlr_max >= word_similarity_threshold)
+ break;
+
+ for (tmp_lower = prev_lower; tmp_lower < lower; tmp_lower++)
+ {
+ int tmp_trgindex;
+ tmp_trgindex = trg2indexes[tmp_lower];
+ if (lastpos[tmp_trgindex] == tmp_lower)
+ lastpos[tmp_trgindex] = -1;
+ }
+ }
+ }
+
+ pfree(lastpos);
+
+ return smlr_max;
+}
+
+/*
+ * Calculate word similarity.
+ * This function prepare two arrays: "trg2indexes" and "found". Then this arrays
+ * are used to calculate word similarity using iterate_word_similarity().
+ *
+ * "trg2indexes" is array which stores indexes of the array "found".
+ * In other words:
+ * trg2indexes[j] = i;
+ * found[i] = true (or false);
+ * If found[i] == true then there is trigram trg2[j] in array "trg1".
+ * If found[i] == false then there is not trigram trg2[j] in array "trg1".
+ *
+ * str1: search pattern string, of length slen1 bytes.
+ * str2: text in which we are looking for a word, of length slen2 bytes.
+ * check_only: if true then only check existaince of similar search pattern in
+ * text.
+ *
+ * Returns word similarity.
+ */
+static float4
+calc_word_similarity(char *str1, int slen1, char *str2, int slen2,
+ bool check_only)
+{
+ bool *found;
+ pos_trgm *ptrg;
+ trgm *trg1;
+ trgm *trg2;
+ int len1,
+ len2,
+ len,
+ i,
+ j,
+ ulen1;
+ int *trg2indexes;
+ float4 result;
+
+ protect_out_of_mem(slen1 + slen2);
+
+ /* Make positional trigrams */
+ trg1 = (trgm *) palloc(sizeof(trgm) * (slen1 / 2 + 1) * 3);
+ trg2 = (trgm *) palloc(sizeof(trgm) * (slen2 / 2 + 1) * 3);
+
+ len1 = generate_trgm_only(trg1, str1, slen1);
+ len2 = generate_trgm_only(trg2, str2, slen2);
+
+ ptrg = make_positional_trgm(trg1, len1, trg2, len2);
+ len = len1 + len2;
+ qsort(ptrg, len, sizeof(pos_trgm), comp_ptrgm);
+
+ pfree(trg1);
+ pfree(trg2);
+
+ /*
+ * Merge positional trigrams array: enumerate each trigram and find its
+ * presence in required word.
+ */
+ trg2indexes = (int *) palloc(sizeof(int) * len2);
+ found = (bool *) palloc0(sizeof(bool) * len);
+
+ ulen1 = 0;
+ j = 0;
+ for (i = 0; i < len; i++)
+ {
+ if (i > 0)
+ {
+ int cmp = CMPTRGM(ptrg[i - 1].trg, ptrg[i].trg);
+ if (cmp != 0)
+ {
+ if (found[j])
+ ulen1++;
+ j++;
+ }
+ }
+
+ if (ptrg[i].index >= 0)
+ {
+ trg2indexes[ptrg[i].index] = j;
+ }
+ else
+ {
+ found[j] = true;
+ }
+ }
+ if (found[j])
+ ulen1++;
+
+ /* Run iterative procedure to find maximum similarity with word */
+ result = iterate_word_similarity(trg2indexes, found, ulen1, len2, len,
+ check_only);
+
+ pfree(trg2indexes);
+ pfree(found);
+ pfree(ptrg);
+
+ return result;
+}
+
+
/*
* Extract the next non-wildcard part of a search string, ie, a word bounded
* by '_' or '%' meta-characters, non-word characters or string end.
@@ -459,17 +793,7 @@ generate_wildcard_trgm(const char *str, int slen)
bytelen;
const char *eword;
- /*
- * Guard against possible overflow in the palloc requests below. (We
- * don't worry about the additive constants, since palloc can detect
- * requests that are a little above MaxAllocSize --- we just need to
- * prevent integer overflow in the multiplications.)
- */
- if ((Size) (slen / 2) >= (MaxAllocSize / (sizeof(trgm) * 3)) ||
- (Size) slen >= (MaxAllocSize / pg_database_encoding_max_length()))
- ereport(ERROR,
- (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
- errmsg("out of memory")));
+ protect_out_of_mem(slen);
trg = (TRGM *) palloc(TRGMHDRSIZE + sizeof(trgm) * (slen / 2 + 1) *3);
trg->flag = ARRKEY;
@@ -590,7 +914,7 @@ show_trgm(PG_FUNCTION_ARGS)
}
float4
-cnt_sml(TRGM *trg1, TRGM *trg2)
+cnt_sml(TRGM *trg1, TRGM *trg2, bool inexact)
{
trgm *ptr1,
*ptr2;
@@ -624,14 +948,15 @@ cnt_sml(TRGM *trg1, TRGM *trg2)
}
}
-#ifdef DIVUNION
- return ((float4) count) / ((float4) (len1 + len2 - count));
-#else
- return ((float4) count) / ((float4) ((len1 > len2) ? len1 : len2));
-#endif
-
+ /*
+ * If inexact then len2 is equal to count, because we don't know actual
+ * length of second string in inexact search and we can assume that count
+ * is a lower bound of len2.
+ */
+ return CALCSML(count, len1, inexact ? count : len2);
}
+
/*
* Returns whether trg2 contains all trigrams in trg1.
* This relies on the trigram arrays being sorted.
@@ -726,7 +1051,7 @@ similarity(PG_FUNCTION_ARGS)
trg1 = generate_trgm(VARDATA(in1), VARSIZE(in1) - VARHDRSZ);
trg2 = generate_trgm(VARDATA(in2), VARSIZE(in2) - VARHDRSZ);
- res = cnt_sml(trg1, trg2);
+ res = cnt_sml(trg1, trg2, false);
pfree(trg1);
pfree(trg2);
@@ -736,6 +1061,22 @@ similarity(PG_FUNCTION_ARGS)
PG_RETURN_FLOAT4(res);
}
+Datum
+word_similarity(PG_FUNCTION_ARGS)
+{
+ text *in1 = PG_GETARG_TEXT_PP(0);
+ text *in2 = PG_GETARG_TEXT_PP(1);
+ float4 res;
+
+ res = calc_word_similarity(VARDATA_ANY(in1), VARSIZE_ANY_EXHDR(in1),
+ VARDATA_ANY(in2), VARSIZE_ANY_EXHDR(in2),
+ false);
+
+ PG_FREE_IF_COPY(in1, 0);
+ PG_FREE_IF_COPY(in2, 1);
+ PG_RETURN_FLOAT4(res);
+}
+
Datum
similarity_dist(PG_FUNCTION_ARGS)
{
@@ -755,3 +1096,67 @@ similarity_op(PG_FUNCTION_ARGS)
PG_RETURN_BOOL(res >= similarity_threshold);
}
+
+Datum
+word_similarity_op(PG_FUNCTION_ARGS)
+{
+ text *in1 = PG_GETARG_TEXT_PP(0);
+ text *in2 = PG_GETARG_TEXT_PP(1);
+ float4 res;
+
+ res = calc_word_similarity(VARDATA_ANY(in1), VARSIZE_ANY_EXHDR(in1),
+ VARDATA_ANY(in2), VARSIZE_ANY_EXHDR(in2),
+ true);
+
+ PG_FREE_IF_COPY(in1, 0);
+ PG_FREE_IF_COPY(in2, 1);
+ PG_RETURN_BOOL(res >= word_similarity_threshold);
+}
+
+Datum
+word_similarity_commutator_op(PG_FUNCTION_ARGS)
+{
+ text *in1 = PG_GETARG_TEXT_PP(0);
+ text *in2 = PG_GETARG_TEXT_PP(1);
+ float4 res;
+
+ res = calc_word_similarity(VARDATA_ANY(in2), VARSIZE_ANY_EXHDR(in2),
+ VARDATA_ANY(in1), VARSIZE_ANY_EXHDR(in1),
+ true);
+
+ PG_FREE_IF_COPY(in1, 0);
+ PG_FREE_IF_COPY(in2, 1);
+ PG_RETURN_BOOL(res >= word_similarity_threshold);
+}
+
+Datum
+word_similarity_dist_op(PG_FUNCTION_ARGS)
+{
+ text *in1 = PG_GETARG_TEXT_PP(0);
+ text *in2 = PG_GETARG_TEXT_PP(1);
+ float4 res;
+
+ res = calc_word_similarity(VARDATA_ANY(in1), VARSIZE_ANY_EXHDR(in1),
+ VARDATA_ANY(in2), VARSIZE_ANY_EXHDR(in2),
+ false);
+
+ PG_FREE_IF_COPY(in1, 0);
+ PG_FREE_IF_COPY(in2, 1);
+ PG_RETURN_FLOAT4(1.0 - res);
+}
+
+Datum
+word_similarity_dist_commutator_op(PG_FUNCTION_ARGS)
+{
+ text *in1 = PG_GETARG_TEXT_PP(0);
+ text *in2 = PG_GETARG_TEXT_PP(1);
+ float4 res;
+
+ res = calc_word_similarity(VARDATA_ANY(in2), VARSIZE_ANY_EXHDR(in2),
+ VARDATA_ANY(in1), VARSIZE_ANY_EXHDR(in1),
+ false);
+
+ PG_FREE_IF_COPY(in1, 0);
+ PG_FREE_IF_COPY(in2, 1);
+ PG_RETURN_FLOAT4(1.0 - res);
+}
diff --git a/doc/src/sgml/pgtrgm.sgml b/doc/src/sgml/pgtrgm.sgml
index 1a9b5a796f1..cdce17251f6 100644
--- a/doc/src/sgml/pgtrgm.sgml
+++ b/doc/src/sgml/pgtrgm.sgml
@@ -92,6 +92,21 @@
(In practice this is seldom useful except for debugging.)
</entry>
</row>
+ <row>
+ <entry>
+ <function>word_similarity(text, text)</function>
+ <indexterm><primary>word_similarity</primary></indexterm>
+ </entry>
+ <entry><type>real</type></entry>
+ <entry>
+ Returns a number that indicates how similar the first string
+ to the most similar word of the second string. The function searches in
+ the second string a most similar word not a most similar substring. The
+ range of the result is zero (indicating that the two strings are
+ completely dissimilar) to one (indicating that the first string is
+ identical to one of the word of the second string).
+ </entry>
+ </row>
<row>
<entry><function>show_limit()</function><indexterm><primary>show_limit</primary></indexterm></entry>
<entry><type>real</type></entry>
@@ -137,6 +152,16 @@
<varname>pg_trgm.similarity_threshold</>.
</entry>
</row>
+ <row>
+ <entry><type>text</> <literal>%></literal> <type>text</></entry>
+ <entry><type>boolean</type></entry>
+ <entry>
+ Returns <literal>true</> if its first argument has the similar word in
+ the second argument and they have a similarity that is greater than the
+ current word similarity threshold set by
+ <varname>pg_trgm.word_similarity_threshold</> parameter.
+ </entry>
+ </row>
<row>
<entry><type>text</> <literal><-></literal> <type>text</></entry>
<entry><type>real</type></entry>
@@ -145,6 +170,16 @@
one minus the <function>similarity()</> value.
</entry>
</row>
+ <row>
+ <entry>
+ <type>text</> <literal><->></literal> <type>text</>
+ </entry>
+ <entry><type>real</type></entry>
+ <entry>
+ Returns the <quote>distance</> between the arguments, that is
+ one minus the <function>word_similarity()</> value.
+ </entry>
+ </row>
</tbody>
</tgroup>
</table>
@@ -168,6 +203,23 @@
</para>
</listitem>
</varlistentry>
+ <varlistentry id="guc-pgtrgm-word-similarity-threshold" xreflabel="pg_trgm.word_similarity_threshold">
+ <term>
+ <varname>pg_trgm.word_similarity_threshold</> (<type>real</type>)
+ <indexterm>
+ <primary>
+ <varname>pg_trgm.word_similarity_threshold</> configuration parameter
+ </primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Sets the current word similarity threshold that is used by
+ the <literal>%></> operator. The threshold must be between
+ 0 and 1 (default is 0.6).
+ </para>
+ </listitem>
+ </varlistentry>
</variablelist>
</sect2>
@@ -225,6 +277,33 @@ SELECT t, t <-> '<replaceable>word</>' AS dist
a small number of the closest matches is wanted.
</para>
+ <para>
+ Also you can use an index on the <structfield>t</> column for word
+ similarity. For example:
+<programlisting>
+SELECT t, word_similarity('<replaceable>word</>', t) AS sml
+ FROM test_trgm
+ WHERE t %> '<replaceable>word</>'
+ ORDER BY sml DESC, t;
+</programlisting>
+ This will return all values in the text column that have a word
+ which sufficiently similar to <replaceable>word</>, sorted from best
+ match to worst. The index will be used to make this a fast operation
+ even over very large data sets.
+ </para>
+
+ <para>
+ A variant of the above query is
+<programlisting>
+SELECT t, t <->> '<replaceable>word</>' AS dist
+ FROM test_trgm
+ ORDER BY dist LIMIT 10;
+</programlisting>
+ This can be implemented quite efficiently by GiST indexes, but not
+ by GIN indexes.
+ </para>
+
+
<para>
Beginning in <productname>PostgreSQL</> 9.1, these index types also support
index searches for <literal>LIKE</> and <literal>ILIKE</>, for example
--
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