parray_gin.md

parray_gin extension

Installing

	CREATE EXTENSION parray_gin;

Extension is compatible with PostgreSQL 9.1 through 14. Description

Extension parray_gin provides GIN index and operator support for arrays with partial match.

Usage

Extension contains operator class named parray_gin_ops for using GIN index with the text arrays. Matching can be strict (array items must be equal) or partial (array items of query may contain like expressions). Surely operators can be used separately from the index.

Index can be created for the table with the following commands:

	-- test table, column `val` needs to be indexed
	create table test_table(id bigserial, val text[]);
	-- create the index
	create index test_tags_idx on test_table using gin (val parray_gin_ops);
	-- select using index
	select * from test_table where val @> array['must','contain'];
	-- select using index
	select * from test_table where val @@> array['what%like%'];

GIN index can be used with three operators: @>, <@, @@>, <@@.

Developers of an extension succesfully used GIN index on JSON arrays extracted from JSON text fields using json_accessors extension.

GIN index is based on trigram decomposition. Trigrams implementation from pg_trgm contrib module is used. Indexed keys are splitted to trigrams which are stored as GIN keys. Query is splitted to trigrams too and carefully checked against GIN keys. Query can contain like expressions which could slow down an index a little. Trigram index can fetch rows with false positive so provided array matching operators recheck fetched rows for sure.

Interface

Operators

@> (text[], text[]) -> bool

Strict array contains. Returns true if LHS array contains all items from the RHS array.

Sample index search:

	$ select * from test_table;
	{star,wars}
	{long,time,ago,in}
	{a,galaxy,far}
	{far,away}
	
	-- must contain any item from right side, strict matched
	$ select * from test_table where val @> array['far'];
	{a,galaxy,far}
	{far,away}

<@ (text[], text[]) -> bool

Strict array contained. Returns true if LHS array is contained by the RHS array.

Sample index search:

	-- must contain all items from right side, partial matched
	$ select * from test_table where val <@ array['galaxy','ago','vader'];
	{long,time,ago,in}
	{a,galaxy,far}

@@> (text[], text[]) -> bool

Partial array contains. Returns true if LHS array contains all items from the RHS array, matched partially (i.e. 'foobar' ~~ 'foo%' or 'foobar' ~~ '%oo%)

Sample index search:

	-- must contain any item from right side, partially matched
	$ select * from test_table where val @@> array['%ar%'];
	{star,wars}

<@@ (text[], text[]) -> bool

Partial array contained by. Returns true if LHS array is contained by all items from the RHS array, matched partially (i.e. foobar contains oobar). Inversion of the @@>.

Sample index search:

	-- must contain all items from right side, partially matched
	$ select * from test_table where val <@@ array['%ar%','vader'];
	{star,wars}

Operator class

operator class parray_gin_ops

GIN-capable operator class. Support indexing strategies based on these operators.

Author

Developed and maintaned by Eugene Seliverstov

Copyright and License

You can use any code from this project under the terms of PostgreSQL License.

Please consult with the COPYING for license information.