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Diffstat (limited to 'doc/src/sgml/storage.sgml')
| -rw-r--r-- | doc/src/sgml/storage.sgml | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml index cda7f6452f..430df4a843 100644 --- a/doc/src/sgml/storage.sgml +++ b/doc/src/sgml/storage.sgml @@ -147,7 +147,9 @@ the relation. The free space map is stored in a file named with the filenode number plus the suffix <literal>_fsm</>. Tables also have a <firstterm>visibility map</>, stored in a fork with the suffix <literal>_vm</>, to track which pages are known to have no dead tuples. The visibility map is -described further in <xref linkend="storage-vm">. +described further in <xref linkend="storage-vm">. Unlogged tables and indexes +have a third fork, known as the initialization fork, which is stored in a fork +with the suffix <literal>_init</literal> (see <xref linkend="storage-init">). </para> <caution> @@ -485,6 +487,24 @@ a bit is not set, it might or might not be true. </sect1> +<sect1 id="storage-init"> + +<title>The Initialization Fork</title> + +<indexterm> + <primary>Initialization Fork</primary> +</indexterm> + +<para> +Each unlogged table, and each index on an unlogged table, has an initialization +fork. The initialization fork is an empty table or index of the appropriate +type. When an unlogged table must be reset to empty due to a crash, the +initialization fork is copied over the main fork, and any other forks are +erased (they will be recreated automatically as needed). +</para> + +</sect1> + <sect1 id="storage-page-layout"> <title>Database Page Layout</title> |