pgstattuple

PostgreSQL 8.4.21 Documentation
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# F.28. pgstattuple

The `pgstattuple` module provides various functions to obtain tuple-level statistics.

## F.28.1. Functions

`pgstattuple(text) returns record`

  `pgstattuple` returns a relation's physical length, percentage of "dead" tuples, and other info. This may help users to determine whether vacuum is necessary or not. The argument is the target relation's name (optionally schema-qualified). For example:

      test=> SELECT * FROM pgstattuple('pg_catalog.pg_proc');
      -[ RECORD 1 ]------+-------
      table_len          | 458752
      tuple_count        | 1470
      tuple_len          | 438896
      tuple_percent      | 95.67
      dead_tuple_count   | 11
      dead_tuple_len     | 3157
      dead_tuple_percent | 0.69
      free_space         | 8932
      free_percent       | 1.95

  The output columns are described in Table F-25.

  Table F-25. `pgstattuple` output columns

  Column | Type | Description
  --- | --- | ---
  `table_len` | `bigint` | Physical relation length in bytes
  `tuple_count` | `bigint` | Number of live tuples
  `tuple_len` | `bigint` | Total length of live tuples in bytes
  `tuple_percent` | `float8` | Percentage of live tuples
  `dead_tuple_count` | `bigint` | Number of dead tuples
  `dead_tuple_len` | `bigint` | Total length of dead tuples in bytes
  `dead_tuple_percent` | `float8` | Percentage of dead tuples
  `free_space` | `bigint` | Total free space in bytes
  `free_percent` | `float8` | Percentage of free space

  `pgstattuple` acquires only a read lock on the relation. So the results do not reflect an instantaneous snapshot; concurrent updates will affect them.

  `pgstattuple` judges a tuple is "dead" if `HeapTupleSatisfiesNow` returns false.

`pgstattuple(oid) returns record`

  This is the same as `pgstattuple(text)`, except that the target relation is specified by OID.

`pgstatindex(text) returns record`

  `pgstatindex` returns a record showing information about a btree index. For example:

      test=> SELECT * FROM pgstatindex('pg_cast_oid_index');
      -[ RECORD 1 ]------+------
      version            | 2
      tree_level         | 0
      index_size         | 8192
      root_block_no      | 1
      internal_pages     | 0
      leaf_pages         | 1
      empty_pages        | 0
      deleted_pages      | 0
      avg_leaf_density   | 50.27
      leaf_fragmentation | 0

  The output columns are:

  Table F-26. `pgstatindex` output columns

  Column | Type | Description
  --- | --- | ---
  `version` | `integer` | Btree version number
  `tree_level` | `integer` | Tree level of the root page
  `index_size` | `bigint` | Total number of pages in index
  `root_block_no` | `bigint` | Location of root block
  `internal_pages` | `bigint` | Number of "internal" (upper-level) pages
  `leaf_pages` | `bigint` | Number of leaf pages
  `empty_pages` | `bigint` | Number of empty pages
  `deleted_pages` | `bigint` | Number of deleted pages
  `avg_leaf_density` | `float8` | Average density of leaf pages
  `leaf_fragmentation` | `float8` | Leaf page fragmentation

  As with `pgstattuple`, the results are accumulated page-by-page, and should not be expected to represent an instantaneous snapshot of the whole index.

`pg_relpages(text) returns bigint`

  `pg_relpages` returns the number of pages in the relation.

## F.28.2. Authors

Tatsuo Ishii and Satoshi Nagayasu

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