Expand Up @@ -8,38 +8,38 @@ ## Introduction The **rum** module provides access method to work with `RUM` index. It is based on the `GIN` accessmethods code. The **rum** module providesan access method to work with a `RUM` index. It is based on the `GIN` accessmethod's code. `GIN` index allowsto perform fast full `tsquery` types. But full A `GIN` index allowsperforming fast full- text search using `tsvector` and`tsquery` types. But full- text search with a GIN index has several problems: - Slow ranking. Itis need position information aboutlexems to ranking. `GIN` index doesn't store positions oflexems . So after indexscan we needadditional heap scan to retrievelexems positions. - Slow phrase search with `GIN` index. This problem relateswith previous problem. Itis need position information to perform phrase search. - Slow ordering by timestamp. `GIN` index can't store some related information in index with lexemes. So it is necessary to perform additional heap scan. - Slow ranking. Itneeds positional information aboutlexemes todo ranking. A `GIN` index doesn't store positions oflexemes . So after indexscanning, we needan additional heap scan to retrievelexeme positions.- Slow phrase search witha `GIN` index. This problem relatesto the previous problem. Itneeds positional information to perform phrase search. - Slow ordering by timestamp.A `GIN` index can't store some related information inthe index with lexemes. So it is necessary to perform an additional heap scan. `RUM` solvesthis problems by storing additional information in posting tree. `RUM` solvesthese problems by storing additional information in a posting tree. For example, positional information of lexemes or timestamps. You can get an idea of `RUM`by the followingpicture : idea of `RUM`with the followingdiagram :  Drawback of `RUM` is that it has slower build and inserttime than `GIN`.It is because we need to store additional information besides keys and because`RUM` uses generic WAL records. A drawback of `RUM` is that it has slower build and inserttimes than `GIN`.This is because we need to store additional information besides keys and because`RUM` uses genericWrite-Ahead Log ( WAL) records. ## License This module available under the [license](LICENSE) similar to This moduleis available under the [license](LICENSE) similar to [PostgreSQL](http://www.postgresql.org/about/licence/). ## Installation Beforebuild andinstall **rum** you should ensure following: Beforebuilding andinstalling **rum**, you should ensure following are installed : * PostgreSQL version is 9.6+. Expand All @@ -62,7 +62,7 @@ Typical installation procedure may look like this: ## Common operators and functions **rum** module provides next operators. The **rum** module provides next operators.| Operator | Returns | Description | -------------------- | ------- | ---------------------------------------------- Expand All @@ -71,19 +71,19 @@ Typical installation procedure may look like this: | timestamp <=| timestamp | float8 | Returns distance only for left timestamps. | timestamp |=> timestamp | float8 | Returns distance only for right timestamps. Last three operations alsoworks for types timestamptz, int2, int4, int8, float4, float8,The last three operations alsowork for types timestamptz, int2, int4, int8, float4, float8,money and oid. ## Operator classes **rum** providesnext operator classes. **rum** providesthe following operator classes. ### rum_tsvector_ops For type: `tsvector` This operator class stores `tsvector` lexemes with positional information.Supports ordering by `<=>` operator and prefix search.There is the example. This operator class stores `tsvector` lexemes with positional information.It supports ordering bythe `<=>` operator and prefix search.See the example below . Let us assume we have the table: Expand Down Expand Up @@ -140,8 +140,8 @@ SELECT t, a <=> to_tsquery('english', 'place | situation') AS rank For type: `tsvector` This operator class stores hash of `tsvector` lexemes with positional information. Supports ordering by `<=>` operator.But **doesn't** support prefix search.This operator class storesa hash of `tsvector` lexemes with positional information. It supports ordering bythe `<=>` operator.It **doesn't** support prefix search.### rum_TYPE_ops Expand All @@ -153,17 +153,18 @@ Supported operations: `<`, `<=`, `=`, `>=`, `>` for all types and `<=>`, `<=|` and `|=>` for int2, int4, int8, float4, float8, money, oid, timestamp and timestamptz types. Supports ordering by `<=>`, `<=|` and `|=>` operators.Can be used withThis operator supports ordering bythe `<=>`, `<=|` and `|=>` operators.It can be used with`rum_tsvector_addon_ops`, `rum_tsvector_hash_addon_ops' and `rum_anyarray_addon_ops` operator classes. ### rum_tsvector_addon_ops For type: `tsvector` This operator class stores `tsvector`lexems with any supported by module field.There is the example. This operator class stores `tsvector`lexemes with any supported by module field.See the example below . Let us assume we have the table: ```sql CREATE TABLE tsts (id int, t tsvector, d timestamp); Expand Down Expand Up @@ -202,16 +203,16 @@ SELECT id, d, d <=> '2016-05-16 14:21:25' FROM tsts WHERE t @@ 'wr&qh' ORDER BY For type: `tsvector` This operator class stores hash of `tsvector`lexems with any supported by module This operator class storesa hash of `tsvector`lexemes with any supported by module field. **Doesn 't** support prefix search.It **doesn 't** support prefix search.### rum_tsquery_ops For type: `tsquery` Stores branches of query tree in additional information. For example we have the table:It stores branches of query tree in additional information. For example, we have the table:```sql CREATE TABLE query (q tsquery, tag text); Expand Down Expand Up @@ -240,8 +241,8 @@ SELECT * FROM query For type: `anyarray` This operator class stores `anyarray` elements with length of the array. Supports operators `&&`, `@>`, `<@`, `=`, `%` operators.Supports ordering by `<=>` operator.For example we have the table: It supports operators `&&`, `@>`, `<@`, `=`, `%` operators.It also supports ordering by `<=>` operator.For example, we have the table: ```sql CREATE TABLE test_array (i int2[]); Expand Down