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Include the backend ID in the relpath of temporary relations.

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This allows us to reliably remove all leftover temporary relation
files on cluster startup without reference to system catalogs or WAL;
therefore, we no longer include temporary relations in XLOG_XACT_COMMIT
and XLOG_XACT_ABORT WAL records.

Since these changes require including a backend ID in each
SharedInvalSmgrMsg, the size of the SharedInvalidationMessage.id
field has been reduced from two bytes to one, and the maximum number
of connections has been reduced from INT_MAX / 4 to 2^23-1.  It would
be possible to remove these restrictions by increasing the size of
SharedInvalidationMessage by 4 bytes, but right now that doesn't seem
like a good trade-off.

Review by Jaime Casanova and Tom Lane.
This commit is contained in:
Robert Haas
2010-08-13 20:10:54 +00:00
parent 3f9479ef3f
commit debcec7dc3
37 changed files with 669 additions and 343 deletions
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26
doc/src/sgml/storage.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.32 2010/02/16 22:34:43 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.33 2010/08/13 20:10:50 rhaas Exp $ -->
<chapter id="storage">
@ -133,16 +133,20 @@ there.
</para>
<para>
Each table and index is stored in a separate file, named after the table
or index's <firstterm>filenode</> number, which can be found in
<structname>pg_class</>.<structfield>relfilenode</>. In addition to the
main file (a/k/a main fork), each table and index has a <firstterm>free space
map</> (see <xref linkend="storage-fsm">), which stores information about free
space available in 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">.
Each table and index is stored in a separate file. For ordinary relations,
these files are named after the table or index's <firstterm>filenode</> number,
which can be found in <structname>pg_class</>.<structfield>relfilenode</>. But
for temporary relations, the file name is of the form
<literal>t<replaceable>BBB</>_<replaceable>FFF</></>, where <replaceable>BBB</>
is the backend ID of the backend which created the file, and <replaceable>FFF</>
is the filenode number. In either case, in addition to the main file (a/k/a
main fork), each table and index has a <firstterm>free space map</> (see <xref
linkend="storage-fsm">), which stores information about free space available in
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">.
</para>
<caution>