47705a8968
* fix: rewrite relative URLs when syncing to GitHub discussion Relative URLs back to supabse.com won't work in GitHub discussions, so rewrite them back to absolute URLs starting with https://supabase.com * fix: replace all supabase urls with relative urls * chore: add linting for relative urls * chore: bump linter version * Prettier --------- Co-authored-by: Chris Chinchilla <chris.ward@supabase.io>
159 lines
4.9 KiB
Plaintext
159 lines
4.9 KiB
Plaintext
---
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id: 'rum'
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title: 'RUM: improved inverted index for full-text search based on GIN index'
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description: 'A GIN-like index with additional tree-organized data for each index entry'
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---
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[RUM](https://github.com/postgrespro/rum) is an extension which adds a RUM index to Postgres.
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RUM index is based on GIN that stores additional per-entry information in a posting tree. For example, positional information of lexemes or timestamps. In comparison to GIN it can use this information to make faster index-only scans for:
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- Phrase search
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- Text search with ranking by text distance operator
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- Text `SELECT`s with ordering by some non-indexed additional column e.g. by timestamp.
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RUM works best in scenarios when the possible keys are highly repeatable. I.e. all texts are composed of a
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limited amount of words, so per-lexeme indexing gives significant speed-up in searching texts containing word
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combinations or phrases.
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Main operators for ordering are:
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`tsvector` `<=>` `tsquery` | `float4` | Distance between `tsvector` and `tsquery`.
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value `<=>` value | `float8` | Distance between two values.
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Where value is `timestamp`, `timestamptz`, `int2`, `int4`, `int8`, `float4`, `float8`, `money` and `oid`
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## Usage
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### Enable the extension
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You can get started with rum by enabling the extension in your Supabase dashboard.
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<Tabs
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scrollable
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size="small"
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type="underlined"
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defaultActiveId="dashboard"
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queryGroup="database-method"
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>
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<TabPanel id="dashboard" label="Dashboard">
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1. Go to the [Database](/dashboard/project/_/database/tables) page in the Dashboard.
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2. Click on **Extensions** in the sidebar.
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3. Search for "rum" and enable the extension.
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</TabPanel>
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<TabPanel id="sql" label="SQL">
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```sql
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-- Example: enable the "rum" extension
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create extension rum with schema extensions;
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-- Example: disable the "rum" extension
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drop extension if exists rum;
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```
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</TabPanel>
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</Tabs>
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### Syntax
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#### For type: `tsvector`
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To understand the following you may need first to see [Official Postgres documentation on text
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search](https://www.postgresql.org/docs/current/functions-textsearch.html)
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`rum_tsvector_ops`
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```sql
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CREATE TABLE test_rum(t text, a tsvector);
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CREATE TRIGGER tsvectorupdate
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BEFORE UPDATE OR INSERT ON test_rum
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FOR EACH ROW EXECUTE PROCEDURE tsvector_update_trigger('a', 'pg_catalog.english', 't');
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INSERT INTO test_rum(t) VALUES ('The situation is most beautiful');
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INSERT INTO test_rum(t) VALUES ('It is a beautiful');
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INSERT INTO test_rum(t) VALUES ('It looks like a beautiful place');
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CREATE INDEX rumidx ON test_rum USING rum (a rum_tsvector_ops);
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```
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And we can execute `tsvector` selects with ordering by text distance operator:
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```sql
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SELECT t, a `<=>` to_tsquery('english', 'beautiful | place') AS rank
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FROM test_rum
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WHERE a @@ to_tsquery('english', 'beautiful | place')
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ORDER BY a `<=>` to_tsquery('english', 'beautiful | place');
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t | rank
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---------------------------------+---------
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It looks like a beautiful place | 8.22467
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The situation is most beautiful | 16.4493
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It is a beautiful | 16.4493
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(3 rows)
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```
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`rum_tsvector_addon_ops`
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```sql
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CREATE TABLE tsts (id int, t tsvector, d timestamp);
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CREATE INDEX tsts_idx ON tsts USING rum (t rum_tsvector_addon_ops, d)
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WITH (attach = 'd', to = 't');
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```
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Now we can execute the selects with ordering distance operator on attached column:
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```sql
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SELECT id, d, d `<=>` '2016-05-16 14:21:25' FROM tsts WHERE t @@ 'wr&qh' ORDER BY d `<=>` '2016-05-16 14:21:25' LIMIT 5;
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id | d | ?column?
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-----+---------------------------------+---------------
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355 | Mon May 16 14:21:22.326724 2016 | 2.673276
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354 | Mon May 16 13:21:22.326724 2016 | 3602.673276
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371 | Tue May 17 06:21:22.326724 2016 | 57597.326724
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406 | Wed May 18 17:21:22.326724 2016 | 183597.326724
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415 | Thu May 19 02:21:22.326724 2016 | 215997.326724
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(5 rows)
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```
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#### For type: `anyarray`
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`rum_anyarray_ops`
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This operator class stores `anyarray` elements with length of the array. It supports operators `&&`, `@>`, `<@`, `=`, `%` operators. It also supports ordering by `<=>` operator.
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```sql
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CREATE TABLE test_array (i int2[]);
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INSERT INTO test_array VALUES ('{}'), ('{0}'), ('{1,2,3,4}'), ('{1,2,3}'), ('{1,2}'), ('{1}');
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CREATE INDEX idx_array ON test_array USING rum (i rum_anyarray_ops);
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```
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Now we can execute the query using index scan:
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```sql
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SELECT * FROM test_array WHERE i && '{1}' ORDER BY i `<=>` '{1}' ASC;
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i
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-----------
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{1}
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{1,2}
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{1,2,3}
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{1,2,3,4}
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(4 rows)
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```
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`rum_anyarray_addon_ops`
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The does the same with `anyarray` index as `rum_tsvector_addon_ops` i.e. allows to order select results using distance
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operator by attached column.
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## Limitations
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`RUM` has slower build and insert times than `GIN` due to:
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1. It is bigger due to the additional attributes stored in the index.
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2. It uses generic WAL records.
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## Resources
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- [Official RUM documentation](https://github.com/postgrespro/rum)
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