6b07ebc181
With a little explain/analyze testing and both gin and gist indexes, it looks like using the <-> operator in combination with a low limit will use the GIST index and work well for basic search-string matching.
32 lines
1.3 KiB
SQL
32 lines
1.3 KiB
SQL
--
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-- Set up search table for text search over locations
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--
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-- uses extension: CREATE EXTENSION pg_trgm;
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--
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CREATE TABLE IF NOT EXISTS search_locations (
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-- internal unique id
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search_id serial PRIMARY KEY,
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-- string to match against in search (E1 0AB / Hackney / Commercial Road...)
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search_str text,
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-- search class for hint (postcode / borough / road name...)
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search_class text,
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-- geometry as EPSG:4326 (lat-long) to be used in front end directly
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center geometry(POINT, 4326),
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-- zoom level
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zoom int
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);
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-- Index for fuzzy match
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-- see https://www.postgresql.org/docs/current/pgtrgm.html
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-- and https://www.postgresql.org/docs/current/textsearch-indexes.html
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--
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-- Should support (I)LIKE or similarity searches:
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-- - SELECT * FROM search_locations WHERE search_str ILIKE 'e1%'
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-- - SELECT *, search_str <-> 'searchterm' AS dist FROM search_locations ORDER BY dist LIMIT 5;
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-- - SELECT *, similarity(search_str, 'searchterm') AS dist FROM search_locations
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-- WHERE t % 'searchterm' ORDER BY dist ASC, t LIMIT 5;
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-- Docs suggest the '<->' query will perform better than the 'similarity', when only a small
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-- number of closest matches are desired, if combined with a GIST index,
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CREATE INDEX trgm_gist_idx_search_str ON search_locations USING GIST (search_str gist_trgm_ops);
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