Package postgresql14-rum: Information

The rum module provides an access method to work with a `RUM` index. It is based
on the `GIN` access method's code.

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 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 these problems by storing additional information in a posting tree.

Package postgresql14-rum: Information

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