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Replace BackendIds with 0-based ProcNumbers

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Now that BackendId was just another index into the proc array, it was
redundant with the 0-based proc numbers used in other places. Replace
all usage of backend IDs with proc numbers.

The only place where the term "backend id" remains is in a few pgstat
functions that expose backend IDs at the SQL level. Those IDs are now
in fact 0-based ProcNumbers too, but the documentation still calls
them "backend ids". That term still seems appropriate to describe what
the numbers are, so I let it be.

One user-visible effect is that pg_temp_0 is now a valid temp schema
name, for backend with ProcNumber 0.

Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/8171f1aa-496f-46a6-afc3-c46fe7a9b407@iki.fi
This commit is contained in:
Heikki Linnakangas
2024-03-03 19:38:22 +02:00
parent ab355e3a88
commit 024c521117
71 changed files with 571 additions and 579 deletions
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2
doc/src/sgml/config.sgml
View File

@ -7495,7 +7495,7 @@ local0.* /var/log/postgresql
</row>
<row>
<entry><literal>%v</literal></entry>
<entry>Virtual transaction ID (backendID/localXID); see
<entry>Virtual transaction ID (procNumber/localXID); see
<xref linkend="transaction-id"/></entry>
<entry>no</entry>
</row>

18
doc/src/sgml/monitoring.sgml
View File

@ -4940,7 +4940,7 @@ description | Waiting for a newly initialized WAL file to reach durable storage
access functions can be used; these are shown in <xref
linkend="monitoring-stats-backend-funcs-table"/>.
These access functions use the session's backend ID number, which is a
small positive integer that is distinct from the backend ID of any
small integer (>= 0) that is distinct from the backend ID of any
concurrent session, although a session's ID can be recycled as soon as
it exits. The backend ID is used, among other things, to identify the
session's temporary schema if it has one.
@ -6813,7 +6813,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg0 contains the fork to be extended. arg1, arg2, and arg3 contain the
tablespace, database, and relation OIDs identifying the relation. arg4
is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared
buffer. arg5 is the number of blocks the caller would like to extend
by.</entry>
</row>
@ -6824,7 +6824,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg0 contains the fork to be extended. arg1, arg2, and arg3 contain the
tablespace, database, and relation OIDs identifying the relation. arg4
is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared
buffer. arg5 is the number of blocks the relation was extended by, this
can be less than the number in the
<literal>buffer-extend-start</literal> due to resource
@ -6839,7 +6839,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
identifying the relation.
arg5 is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared buffer.
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.
</entry>
</row>
<row>
@ -6850,7 +6850,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
identifying the relation.
arg5 is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared buffer.
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.
arg6 is true if the buffer was found in the pool, false if not.</entry>
</row>
<row>
@ -6903,7 +6903,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
identifying the relation.
arg5 is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared buffer.</entry>
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.</entry>
</row>
<row>
<entry><literal>smgr-md-read-done</literal></entry>
@ -6913,7 +6913,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
identifying the relation.
arg5 is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared buffer.
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.
arg6 is the number of bytes actually read, while arg7 is the number
requested (if these are different it indicates a short read).</entry>
</row>
@ -6925,7 +6925,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
identifying the relation.
arg5 is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared buffer.</entry>
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.</entry>
</row>
<row>
<entry><literal>smgr-md-write-done</literal></entry>
@ -6935,7 +6935,7 @@ FROM pg_stat_get_backend_idset() AS backendid;
arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
identifying the relation.
arg5 is the ID of the backend which created the temporary relation for a
local buffer, or <symbol>InvalidBackendId</symbol> (-1) for a shared buffer.
local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.
arg6 is the number of bytes actually written, while arg7 is the number
requested (if these are different it indicates a short write).</entry>
</row>

2
doc/src/sgml/storage.sgml
View File

@ -202,7 +202,7 @@ these files are named after the table or index's <firstterm>filenode</firstterm>
which can be found in <structname>pg_class</structname>.<structfield>relfilenode</structfield>. But
for temporary relations, the file name is of the form
<literal>t<replaceable>BBB</replaceable>_<replaceable>FFF</replaceable></literal>, where <replaceable>BBB</replaceable>
is the backend ID of the backend which created the file, and <replaceable>FFF</replaceable>
is the process number of the backend which created the file, and <replaceable>FFF</replaceable>
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</firstterm> (see <xref
linkend="storage-fsm"/>), which stores information about free space available in

4
doc/src/sgml/xact.sgml
View File

@ -26,10 +26,10 @@
Every transaction is identified by a unique
<literal>VirtualTransactionId</literal> (also called
<literal>virtualXID</literal> or <literal>vxid</literal>), which
is comprised of a backend ID (or <literal>backendID</literal>)
is comprised of a backend's process number (or <literal>procNumber</literal>)
and a sequentially-assigned number local to each backend, known as
<literal>localXID</literal>. For example, the virtual transaction
ID <literal>4/12532</literal> has a <literal>backendID</literal>
ID <literal>4/12532</literal> has a <literal>procNumber</literal>
of <literal>4</literal> and a <literal>localXID</literal> of
<literal>12532</literal>.
</para>