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Commitd1e0272

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Replace the pg_listener-based LISTEN/NOTIFY mechanism with an in-memory queue.
In addition, add support for a "payload" string to be passed along witheach notify event.This implementation should be significantly more efficient than the old one,and is also more compatible with Hot Standby usage. There is not yet anyfacility for HS slaves to receive notifications generated on the master,although such a thing is possible in future.Joachim Wieland, reviewed by Jeff Davis; also hacked on by me.
1 parentfc5173a commitd1e0272

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37 files changed

+1843
-756
lines changed

37 files changed

+1843
-756
lines changed

‎doc/src/sgml/catalogs.sgml‎

Lines changed: 1 addition & 68 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.221 2010/02/07 20:48:09 tgl Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.222 2010/02/16 22:34:41 tgl Exp $ -->
22
<!--
33
Documentation of the system catalogs, directed toward PostgreSQL developers
44
-->
@@ -168,11 +168,6 @@
168168
<entry>metadata for large objects</entry>
169169
</row>
170170

171-
<row>
172-
<entry><link linkend="catalog-pg-listener"><structname>pg_listener</structname></link></entry>
173-
<entry>asynchronous notification support</entry>
174-
</row>
175-
176171
<row>
177172
<entry><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link></entry>
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<entry>schemas</entry>
@@ -3253,68 +3248,6 @@
32533248
</table>
32543249
</sect1>
32553250

3256-
<sect1 id="catalog-pg-listener">
3257-
<title><structname>pg_listener</structname></title>
3258-
3259-
<indexterm zone="catalog-pg-listener">
3260-
<primary>pg_listener</primary>
3261-
</indexterm>
3262-
3263-
<para>
3264-
The catalog <structname>pg_listener</structname> supports the
3265-
<xref linkend="sql-listen" endterm="sql-listen-title"> and
3266-
<xref linkend="sql-notify" endterm="sql-notify-title">
3267-
commands. A listener creates an entry in
3268-
<structname>pg_listener</structname> for each notification name
3269-
it is listening for. A notifier scans <structname>pg_listener</structname>
3270-
and updates each matching entry to show that a notification has occurred.
3271-
The notifier also sends a signal (using the PID recorded in the table)
3272-
to awaken the listener from sleep.
3273-
</para>
3274-
3275-
<table>
3276-
<title><structname>pg_listener</> Columns</title>
3277-
3278-
<tgroup cols="3">
3279-
<thead>
3280-
<row>
3281-
<entry>Name</entry>
3282-
<entry>Type</entry>
3283-
<entry>Description</entry>
3284-
</row>
3285-
</thead>
3286-
3287-
<tbody>
3288-
<row>
3289-
<entry><structfield>relname</structfield></entry>
3290-
<entry><type>name</type></entry>
3291-
<entry>
3292-
Notify condition name. (The name need not match any actual
3293-
relation in the database; the name <structfield>relname</> is historical.)
3294-
</entry>
3295-
</row>
3296-
3297-
<row>
3298-
<entry><structfield>listenerpid</structfield></entry>
3299-
<entry><type>int4</type></entry>
3300-
<entry>PID of the server process that created this entry</entry>
3301-
</row>
3302-
3303-
<row>
3304-
<entry><structfield>notification</structfield></entry>
3305-
<entry><type>int4</type></entry>
3306-
<entry>
3307-
Zero if no event is pending for this listener. If an event is
3308-
pending, the PID of the server process that sent the notification
3309-
</entry>
3310-
</row>
3311-
</tbody>
3312-
</tgroup>
3313-
</table>
3314-
3315-
</sect1>
3316-
3317-
33183251
<sect1 id="catalog-pg-namespace">
33193252
<title><structname>pg_namespace</structname></title>
33203253

‎doc/src/sgml/func.sgml‎

Lines changed: 17 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.503 2010/02/1621:18:01 momjian Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.504 2010/02/1622:34:42 tgl Exp $ -->
22

33
<chapter id="functions">
44
<title>Functions and Operators</title>
@@ -11529,6 +11529,12 @@ postgres=# select * from unnest2(array[[1,2],[3,4]]);
1152911529
</entry>
1153011530
</row>
1153111531

11532+
<row>
11533+
<entry><literal><function>pg_listening_channels</function>()</literal></entry>
11534+
<entry><type>setof text</type></entry>
11535+
<entry>channel names that the session is currently listening on</entry>
11536+
</row>
11537+
1153211538
<row>
1153311539
<entry><literal><function>inet_client_addr</function>()</literal></entry>
1153411540
<entry><type>inet</type></entry>
@@ -11674,6 +11680,16 @@ SET search_path TO <replaceable>schema</> <optional>, <replaceable>schema</>, ..
1167411680
</para>
1167511681
</note>
1167611682

11683+
<indexterm>
11684+
<primary>pg_listening_channels</primary>
11685+
</indexterm>
11686+
11687+
<para>
11688+
<function>pg_listening_channels</function> returns a set of names of
11689+
channels that the current session is listening to. See <xref
11690+
linkend="sql-listen" endterm="sql-listen-title"> for more information.
11691+
</para>
11692+
1167711693
<indexterm>
1167811694
<primary>inet_client_addr</primary>
1167911695
</indexterm>

‎doc/src/sgml/libpq.sgml‎

Lines changed: 25 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.298 2010/02/1620:58:13 momjian Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.299 2010/02/1622:34:42 tgl Exp $ -->
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33
<chapter id="libpq">
44
<title><application>libpq</application> - C Library</title>
@@ -307,28 +307,28 @@
307307
<entry>Description</entry>
308308
</row>
309309
</thead>
310-
310+
311311
<tbody>
312-
312+
313313
<row>
314314
<entry><literal>disable</></entry>
315315
<entry>only try a non-<acronym>SSL</> connection</entry>
316316
</row>
317-
317+
318318
<row>
319319
<entry><literal>allow</></entry>
320320
<entry>first try a non-<acronym>SSL</>
321321
connection; if that fails, try an <acronym>SSL</>
322322
connection</entry>
323323
</row>
324-
324+
325325
<row>
326326
<entry><literal>prefer</> (default)</entry>
327327
<entry>first try an <acronym>SSL</> connection; if
328328
that fails, try a non-<acronym>SSL</>
329329
connection</entry>
330330
</row>
331-
331+
332332
<row>
333333
<entry><literal>require</></entry>
334334
<entry>only try an <acronym>SSL</> connection</entry>
@@ -481,7 +481,7 @@
481481
</para>
482482

483483
<para>
484-
If <literal>expand_dbname</literal> is non-zero and
484+
If <literal>expand_dbname</literal> is non-zero and
485485
<parameter>dbname</parameter> contains an <symbol>=</symbol> sign, it
486486
is taken as a <parameter>conninfo</parameter> string in exactly the same way as
487487
if it had been passed to <function>PQconnectdb</function>(see below). Previously
@@ -4111,50 +4111,48 @@ typedef struct {
41114111
<productname>PostgreSQL</productname> offers asynchronous notification
41124112
via the <command>LISTEN</command> and <command>NOTIFY</command>
41134113
commands. A client session registers its interest in a particular
4114-
notificationcondition with the <command>LISTEN</command> command (and
4114+
notificationchannel with the <command>LISTEN</command> command (and
41154115
can stop listening with the <command>UNLISTEN</command> command). All
4116-
sessions listening on a particularcondition will be notified
4116+
sessions listening on a particularchannel will be notified
41174117
asynchronously when a <command>NOTIFY</command> command with that
4118-
condition name is executed by any session. No additional information
4119-
is passed from the notifier to the listener. Thus, typically, any
4120-
actual data that needs to be communicated is transferred through a
4121-
database table. Commonly, the condition name is the same as the
4122-
associated table, but it is not necessary for there to be any associated
4123-
table.
4118+
channel name is executed by any session. A <quote>payload</> string can
4119+
be passed to communicate additional data to the listeners.
41244120
</para>
41254121

41264122
<para>
41274123
<application>libpq</application> applications submit
4128-
<command>LISTEN</command> and <command>UNLISTEN</command> commands as
4124+
<command>LISTEN</command>, <command>UNLISTEN</command>,
4125+
and <command>NOTIFY</command> commands as
41294126
ordinary SQL commands. The arrival of <command>NOTIFY</command>
41304127
messages can subsequently be detected by calling
41314128
<function>PQnotifies</function>.<indexterm><primary>PQnotifies</></>
41324129
</para>
41334130

41344131
<para>
4135-
The function <function>PQnotifies</function>
4136-
returnsthenext notification from a list of unhandled
4137-
notification messages received from the server.It returns a null pointer if
4138-
there are no pending notifications. Once a notification is
4139-
returnedfrom<function>PQnotifies</>, it is considered handled and will be
4140-
removed from the list of notifications.
4132+
The function <function>PQnotifies</function> returns the next notification
4133+
from a list of unhandled notification messages received fromtheserver.
4134+
It returns a null pointer if there are no pending notifications.Once a
4135+
notification is returned from <function>PQnotifies</>, it is considered
4136+
handled and will be removedfromthe list of notifications.
4137+
41414138
<synopsis>
41424139
PGnotify *PQnotifies(PGconn *conn);
41434140

41444141
typedef struct pgNotify {
4145-
char *relname; /* notificationcondition name */
4142+
char *relname; /* notificationchannel name */
41464143
int be_pid; /* process ID of notifying server process */
4147-
char *extra; /* notificationparameter */
4144+
char *extra; /* notificationpayload string */
41484145
} PGnotify;
41494146
</synopsis>
4147+
41504148
After processing a <structname>PGnotify</structname> object returned
41514149
by <function>PQnotifies</function>, be sure to free it with
41524150
<function>PQfreemem</function>. It is sufficient to free the
41534151
<structname>PGnotify</structname> pointer; the
41544152
<structfield>relname</structfield> and <structfield>extra</structfield>
4155-
fields do not represent separate allocations. (At present, the
4156-
<structfield>extra</structfield> field is unused and will always point
4157-
to an empty string.)
4153+
fields do not represent separate allocations. (The names of these fields
4154+
are historical; in particular, channel names need not have anything to
4155+
do with relation names.)
41584156
</para>
41594157

41604158
<para>

‎doc/src/sgml/protocol.sgml‎

Lines changed: 10 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.80 2010/02/1620:58:14 momjian Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.81 2010/02/1622:34:43 tgl Exp $ -->
22

33
<chapter id="protocol">
44
<title>Frontend/Backend Protocol</title>
@@ -354,7 +354,7 @@
354354
<para>
355355
This message contains the response data from the previous step
356356
of GSSAPI or SSPI negotiation (AuthenticationGSS, AuthenticationSSPI
357-
or a previous AuthenticationGSSContinue). If the GSSAPI
357+
or a previous AuthenticationGSSContinue). If the GSSAPI
358358
or SSPI data in this message
359359
indicates more data is needed to complete the authentication,
360360
the frontend must send that data as another PasswordMessage. If
@@ -992,7 +992,7 @@
992992

993993
<para>
994994
In the event of a backend-detected error during copy-in mode (including
995-
receipt of a CopyFail message), the backend will issue an ErrorResponse
995+
receipt of a CopyFail message), the backend will issue an ErrorResponse
996996
message. If the <command>COPY</> command was issued via an extended-query
997997
message, the backend will now discard frontend messages until a Sync
998998
message is received, then it will issue ReadyForQuery and return to normal
@@ -1117,7 +1117,7 @@
11171117
backend will send a NotificationResponse message (not to be
11181118
confused with NoticeResponse!) whenever a
11191119
<command>NOTIFY</command> command is executed for the same
1120-
notification name.
1120+
channel name.
11211121
</para>
11221122

11231123
<note>
@@ -1340,7 +1340,7 @@ This section describes the base data types used in messages.
13401340
value that will appear, otherwise the value is variable.
13411341
Eg. String, String("user").
13421342
</para>
1343-
1343+
13441344
<note>
13451345
<para>
13461346
<emphasis>There is no predefined limit</emphasis> on the length of a string
@@ -1951,7 +1951,7 @@ Bind (F)
19511951
(denoted <replaceable>R</> below).
19521952
This can be zero to indicate that there are no result columns
19531953
or that the result columns should all use the default format
1954-
(text);
1954+
(text);
19551955
or one, in which case the specified format code is applied
19561956
to all result columns (if any); or it can equal the actual
19571957
number of result columns of the query.
@@ -2500,7 +2500,7 @@ CopyOutResponse (B)
25002500
separated by separator characters, etc). 1 indicates
25012501
the overall copy format is binary (similar to DataRow
25022502
format). See <xref linkend="sql-copy"
2503-
endterm="sql-copy-title"> for more information.
2503+
endterm="sql-copy-title"> for more information.
25042504
</para>
25052505
</listitem>
25062506
</varlistentry>
@@ -3187,7 +3187,7 @@ NotificationResponse (B)
31873187
</term>
31883188
<listitem>
31893189
<para>
3190-
The name of thecondition that the notify has been raised on.
3190+
The name of thechannel that the notify has been raised on.
31913191
</para>
31923192
</listitem>
31933193
</varlistentry>
@@ -3197,9 +3197,7 @@ NotificationResponse (B)
31973197
</term>
31983198
<listitem>
31993199
<para>
3200-
Additional information passed from the notifying process.
3201-
(Currently, this feature is unimplemented so the field
3202-
is always an empty string.)
3200+
The <quote>payload</> string passed from the notifying process.
32033201
</para>
32043202
</listitem>
32053203
</varlistentry>
@@ -4353,7 +4351,7 @@ the backend.
43534351

43544352
<para>
43554353
The NotificationResponse ('<literal>A</>') message has an additional string
4356-
field, whichis presently empty but might somedaycarryadditional data passed
4354+
field, whichcancarrya <quote>payload</> string passed
43574355
from the <command>NOTIFY</command> event sender.
43584356
</para>
43594357

@@ -4364,5 +4362,4 @@ string parameter; this has been removed.
43644362

43654363
</sect1>
43664364

4367-
43684365
</chapter>

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