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Fix parsing of complex morphs to tsquery

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When to_tsquery() or websearch_to_tsquery() meet a complex morph containing
multiple words residing adjacent position, these words are connected
with OP_AND operator.  That leads to surprising results.  For instace,
both websearch_to_tsquery('"pg_class pg"') and to_tsquery('pg_class <-> pg')
produce '( pg & class ) <-> pg' tsquery.  This tsquery requires
'pg' and 'class' words to reside on the same position and doesn't match
to to_tsvector('pg_class pg').  It appears to be ridiculous behavior, which
needs to be fixed.

This commit makes to_tsquery() or websearch_to_tsquery() connect words
residing adjacent position with OP_PHRASE.  Therefore, now those words are
normally chained with other OP_PHRASE operator.  The examples of above now
produces 'pg <-> class <-> pg' tsquery, which matches to
to_tsvector('pg_class pg').

Another effect of this commit is that complex morph word positions now need to
match the tsvector even if there is no surrounding OP_PHRASE.  This behavior
change generally looks like an improvement but making this commit not
backpatchable.

Reported-by: Barry Pederson
Bug: #16592
Discussion: https://postgr.es/m/16592-70b110ff9731c07d@postgresql.org
Discussion: https://postgr.es/m/CAPpHfdv0EzVhf6CWfB1_TTZqXV_2Sn-jSY3zSd7ePH%3D-%2B1V2DQ%40mail.gmail.com
Author: Alexander Korotkov
Reviewed-by: Tom Lane, Neil Chen
This commit is contained in:
Alexander Korotkov
2021-01-31 20:14:29 +03:00
parent dfb75e478c
commit 0c4f355c6a
3 changed files with 132 additions and 97 deletions
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41
src/backend/tsearch/to_tsany.c
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@@ -20,10 +20,20 @@
#include "utils/jsonfuncs.h"
/*
* Opaque data structure, which is passed by parse_tsquery() to pushval_morph().
*/
typedef struct MorphOpaque
{
Oid cfg_id;
int qoperator; /* query operator */
/*
* Single tsquery morph could be parsed into multiple words. When these
* words reside in adjacent positions, they are connected using this
* operator. Usually, that is OP_PHRASE, which requires word positions of
* a complex morph to exactly match the tsvector.
*/
int qoperator;
} MorphOpaque;
typedef struct TSVectorBuildState
@@ -573,7 +583,14 @@ to_tsquery_byid(PG_FUNCTION_ARGS)
MorphOpaque data;
data.cfg_id = PG_GETARG_OID(0);
data.qoperator = OP_AND;
/*
* Passing OP_PHRASE as a qoperator makes tsquery require matching of word
* positions of a complex morph exactly match the tsvector. Also, when
* the complex morphs are connected with OP_PHRASE operator, we connect
* all their words into the OP_PHRASE sequence.
*/
data.qoperator = OP_PHRASE;
query = parse_tsquery(text_to_cstring(in),
pushval_morph,
@@ -603,6 +620,12 @@ plainto_tsquery_byid(PG_FUNCTION_ARGS)
MorphOpaque data;
data.cfg_id = PG_GETARG_OID(0);
/*
* parse_tsquery() with P_TSQ_PLAIN flag takes the whole input text as a
* single morph. Passing OP_PHRASE as a qoperator makes tsquery require
* matching of all words independently on their positions.
*/
data.qoperator = OP_AND;
query = parse_tsquery(text_to_cstring(in),
@@ -634,6 +657,12 @@ phraseto_tsquery_byid(PG_FUNCTION_ARGS)
MorphOpaque data;
data.cfg_id = PG_GETARG_OID(0);
/*
* parse_tsquery() with P_TSQ_PLAIN flag takes the whole input text as a
* single morph. Passing OP_PHRASE as a qoperator makes tsquery require
* matching of word positions.
*/
data.qoperator = OP_PHRASE;
query = parse_tsquery(text_to_cstring(in),
@@ -665,7 +694,13 @@ websearch_to_tsquery_byid(PG_FUNCTION_ARGS)
data.cfg_id = PG_GETARG_OID(0);
data.qoperator = OP_AND;
/*
* Passing OP_PHRASE as a qoperator makes tsquery require matching of word
* positions of a complex morph exactly match the tsvector. Also, when
* the complex morphs are given in quotes, we connect all their words into
* the OP_PHRASE sequence.
*/
data.qoperator = OP_PHRASE;
query = parse_tsquery(text_to_cstring(in),
pushval_morph,