From 775de3bc1af14d53f9f6d4dd7882f96c7187cb84 Mon Sep 17 00:00:00 2001 From: Jacqui Shadforth Date: Sun, 18 Sep 2022 20:22:07 +0100 Subject: [PATCH] Update README with small language tweaks --- README.md | 67 ++++++++++++++++++++++++++++--------------------------- 1 file changed, 34 insertions(+), 33 deletions(-) diff --git a/README.md b/README.md index 667e1a3586..5f3e6887cf 100644 --- a/README.md +++ b/README.md @@ -8,38 +8,38 @@ ## Introduction -The **rum** module provides access method to work with `RUM` index. It is based -on the `GIN` access methods code. +The **rum** module provides an access method to work with a `RUM` index. It is based +on the `GIN` access method's code. -`GIN` index allows to perform fast full text search using `tsvector` and -`tsquery` types. But full text search with GIN index has several problems: +A `GIN` index allows performing fast full-text search using `tsvector` and +`tsquery` types. But full-text search with a GIN index has several problems: -- Slow ranking. It is need position information about lexems to ranking. `GIN` -index doesn't store positions of lexems. So after index scan we need additional -heap scan to retrieve lexems positions. -- Slow phrase search with `GIN` index. This problem relates with previous -problem. It is 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. It needs positional information about lexemes to do ranking. A `GIN` +index doesn't store positions of lexemes. So after index scanning, we need an +additional heap scan to retrieve lexeme positions. +- Slow phrase search with a `GIN` index. This problem relates to the previous +problem. It needs positional information to perform phrase search. +- Slow ordering by timestamp. A `GIN` index can't store some related information +in the index with lexemes. So it is necessary to perform an additional heap scan. -`RUM` solves this problems by storing additional information in posting tree. +`RUM` solves these 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 following picture: +idea of `RUM` with the following diagram: ![How RUM stores additional information](img/gin_rum.png) -Drawback of `RUM` is that it has slower build and insert time 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 insert times than `GIN`. +This is because we need to store additional information besides keys and because +`RUM` uses generic Write-Ahead Log (WAL) records. ## License -This module available under the [license](LICENSE) similar to +This module is available under the [license](LICENSE) similar to [PostgreSQL](http://www.postgresql.org/about/licence/). ## Installation -Before build and install **rum** you should ensure following: +Before building and installing **rum**, you should ensure following are installed: * PostgreSQL version is 9.6+. @@ -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 | -------------------- | ------- | ---------------------------------------------- @@ -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 also works for types timestamptz, int2, int4, int8, float4, float8, +The last three operations also work for types timestamptz, int2, int4, int8, float4, float8, money and oid. ## Operator classes -**rum** provides next operator classes. +**rum** provides the 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 by the `<=>` operator and prefix search. See the example below. Let us assume we have the table: @@ -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 stores a hash of `tsvector` lexemes with positional information. +It supports ordering by the `<=>` operator. It **doesn't** support prefix search. ### rum_TYPE_ops @@ -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 with +This operator supports ordering by the `<=>`, `<=|` 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); @@ -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 stores a 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); @@ -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[]); pFad - Phonifier reborn

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