I need to make search-as-you-type autocomplete for a large list of companies (over 80,000,000). The company name should contain the word that starts with a search query like this
+-------+----------------------------------+
| term | results |
+-------+----------------------------------+
| gen | general motors; general electric |
| geno | genoptix; genomic health |
| genom | genoma group; genomic health |
+-------+----------------------------------+
The pg_trgm module and GIN index implement similar behavior but don't solve my problem.
For example, ElasticSearch has feature Edge NGram Tokenizer that completely fits my requirements.
From documentation:
The edge_ngram tokenizer first breaks the text down into words
whenever it encounters one of a list of specified characters,
then it emits N-grams of each word
where the start of the N-gram is anchored to the beginning of the word.
Edge N-Grams are useful for search-as-you-type queries.
Is there a similar solution in PostgreSQL?
I create a custom tokenizer
CREATE OR REPLACE FUNCTION edge_gram_tsvector(text text) RETURNS tsvector AS
$BODY$
BEGIN
RETURN (select array_to_tsvector((select array_agg(distinct substring(lexeme for len)) from unnest(to_tsvector(text)), generate_series(1,length(lexeme)) len)));
END;
$BODY$
IMMUTABLE
language plpgsql;
This function creates all edge ngrams like this
postgres=# select edge_gram_tsvector('general electric');
edge_gram_tsvector
-----------------------------------------------------------------------------------------
'e' 'el' 'ele' 'elec' 'elect' 'electr' 'g' 'ge' 'gen' 'gene' 'gener' 'genera' 'general'
(1 row)
Then I create a GIN index for tsquery
create index on company using gin(edge_gram_tsvector(name));
The search query will look like this
b2bdb_master=# select name from company where edge_gram_tsvector(name) @@ 'electric'::tsquery limit 3;
name
--------------------------------------------
General electric
Electriciantalk
Galesburg Electric Industrial Supply
(3 rows)
Performance of solution is quite high
explain analyse select * from company where edge_gram_tsvector(name) @@ 'electric'::tsquery;
Bitmap Heap Scan on company (cost=175.13..27450.31 rows=20752 width=2247) (actual time=0.224..1.019 rows=343 loops=1)
Recheck Cond: (edge_gram_tsvector((name)::text) @@ '''electric'''::tsquery)
Heap Blocks: exact=342
-> Bitmap Index Scan on company_edge_gram_tsvector_idx (cost=0.00..169.94 rows=20752 width=0) (actual time=0.138..0.138 rows=343 loops=1)
Index Cond: (edge_gram_tsvector((name)::text) @@ '''electric'''::tsquery)
Planning Time: 0.216 ms
Execution Time: 1.100 ms