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Adjust /contrib/pg_freespace to show index free space as NULL (FSM only

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tracks index pages, not free space on pages):

1/ Index free bytes set to NULL
2/ Comment added to the README briefly mentioning the index business
3/ Columns reordered more logically
4/ 'Blockid' column removed
5/ Free bytes column renamed to just 'bytes' instead of 'blockfreebytes'

Mark Kirkwood
This commit is contained in:
Bruce Momjian
2006-04-26 22:41:18 +00:00
parent 59d61409cd
commit 028ec5cb0f
3 changed files with 71 additions and 50 deletions
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48
contrib/pg_freespacemap/README.pg_freespacemap
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@ -34,12 +34,12 @@ Notes
Column | references | Description
----------------+----------------------+------------------------------------
blockid | | Id, 1.. max_fsm_pages
relfilenode | pg_class.relfilenode | Refilenode of the relation.
reltablespace | pg_tablespace.oid | Tablespace oid of the relation.
reldatabase | pg_database.oid | Database for the relation.
relfilenode | pg_class.relfilenode | Refilenode of the relation.
relblocknumber | | Offset of the page in the relation.
blockfreebytes | | Free bytes in the block/page.
bytes | | Free bytes in the block/page, or NULL
| | for an index page (see below).
There is one row for each page in the free space map.
@ -47,6 +47,9 @@ Notes
Because the map is shared by all the databases, there are pages from
relations not belonging to the current database.
The free space map can contain pages for btree indexes if they were emptied
by a vacuum process. The bytes field is set to NULL in this case.
When the pg_freespacemap view is accessed, internal free space map locks are
taken, and a copy of the map data is made for the view to display.
This ensures that the view produces a consistent set of results, while not
@ -58,34 +61,33 @@ Sample output
-------------
regression=# \d pg_freespacemap
View "public.pg_freespacemap"
View "public.pg_freespacemap"
Column | Type | Modifiers
---------------+---------+-----------
blockid | integer |
relfilenode | oid |
----------------+---------+-----------
reltablespace | oid |
reldatabase | oid |
relfilenode | oid |
relblocknumber | bigint |
blockfreebytes | integer |
bytes | integer |
View definition:
SELECT p.blockid, p.relfilenode, p.reltablespace, p.reldatabase, p.relblocknumber, p.blockfreebytes
FROM pg_freespacemap() p(blockid integer, relfilenode oid, reltablespace oid, reldatabase oid, relblocknumber bigint, blockfreebytes integer);
SELECT p.reltablespace, p.reldatabase, p.relfilenode, p.relblocknumber, p.bytes
FROM pg_freespacemap() p(reltablespace oid, reldatabase oid, relfilenode oid, relblocknumber bigint, bytes integer);
regression=# SELECT c.relname, m.relblocknumber, m.blockfreebytes
regression=# SELECT c.relname, m.relblocknumber, m.bytes
FROM pg_freespacemap m INNER JOIN pg_class c
ON c.relfilenode = m.relfilenode LIMIT 10;
relname | relblocknumber | blockfreebytes
------------------------+----------------+----------------
sql_features | 5 | 2696
sql_implementation_info | 0 | 7104
sql_languages | 0 | 8016
sql_packages | 0 | 7376
sql_sizing | 0 | 6032
pg_authid | 0 | 7424
pg_toast_2618 | 13 | 4588
pg_toast_2618 | 12 | 1680
pg_toast_2618 | 10 | 1436
pg_toast_2618 | 7 | 1136
relname | relblocknumber | bytes
------------------------+----------------+--------
sql_features | 5 | 2696
sql_implementation_info | 0 | 7104
sql_languages | 0 | 8016
sql_packages | 0 | 7376
sql_sizing | 0 | 6032
pg_authid | 0 | 7424
pg_toast_2618 | 13 | 4588
pg_toast_2618 | 12 | 1680
pg_toast_2618 | 10 | 1436
pg_toast_2618 | 7 | 1136
(10 rows)
regression=#