pgstattuple

PostgreSQL 9.3.20 Documentation
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The pgstattuple module provides various functions to obtain tuple-level statistics.

F.29.1. 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-23 .

Table F-23. 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

Note: The table_len will always be greater than the sum of the tuple_len , dead_tuple_len and free_space . The difference is accounted for by fixed page overhead, the per-page table of pointers to tuples, and padding to ensure that tuples are correctly aligned.

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 B-tree index. For example:

test=> SELECT * FROM pgstatindex('pg_cast_oid_index');
-[ RECORD 1 ]------+------
version            | 2
tree_level         | 0
index_size         | 16384
root_block_no      | 1
internal_pages     | 0
leaf_pages         | 1
empty_pages        | 0
deleted_pages      | 0
avg_leaf_density   | 54.27
leaf_fragmentation | 0

The output columns are:

Column	Type	Description
`version`	`integer`	B-tree version number
`tree_level`	`integer`	Tree level of the root page
`index_size`	`bigint`	Total index size in bytes
`root_block_no`	`bigint`	Location of root page (zero if none)
`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

The reported index_size will normally correspond to one more page than is accounted for by internal_pages + leaf_pages + empty_pages + deleted_pages , because it also includes the index's metapage.

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

pgstatginindex(regclass) returns record

pgstatginindex returns a record showing information about a GIN index. For example:

test=> SELECT * FROM pgstatginindex('test_gin_index');
-[ RECORD 1 ]--+--
version        | 1
pending_pages  | 0
pending_tuples | 0

The output columns are:

Column	Type	Description
`version`	`integer`	GIN version number
`pending_pages`	`integer`	Number of pages in the pending list
`pending_tuples`	`bigint`	Number of tuples in the pending list

pg_relpages(text) returns bigint

pg_relpages returns the number of pages in the relation.

F.29.2. Authors

Tatsuo Ishii and Satoshi Nagayasu

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