Include the backend ID in the relpath of temporary relations.

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.

1 files changed, 15 insertions, 11 deletions

diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index c4b38ddb6c8..46bb03432da 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -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>