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psql: Allow queries terminated by semicolons while in pipeline mode
Currently, the only way to pipe queries in an ongoing pipeline (in a \startpipeline block) is to leverage the meta-commands able to create extended queries such as \bind, \parse or \bind_named. While this is good enough for testing the backend with pipelines, it has been mentioned that it can also be very useful to allow queries terminated by semicolons to be appended to a pipeline. For example, it would be possible to migrate existing psql scripts to use pipelines by just adding a set of \startpipeline and \endpipeline meta-commands, making such scripts more efficient. Doing such a change is proving to be simple in psql: queries terminated by semicolons can be executed through PQsendQueryParams() without any parameters set when the pipeline mode is active, instead of PQsendQuery(), the default, like pgbench. \watch is still forbidden while in a pipeline, as it expects its results to be processed synchronously. The large portion of this commit consists in providing more test coverage, with mixes of extended queries appended in a pipeline by \bind and friends, and queries terminated by semicolons. This improvement has been suggested by Daniel Vérité. Author: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com> Discussion: https://postgr.es/m/d67b9c19-d009-4a50-8020-1a0ea92366a1@manitou-mail.org
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‎doc/src/sgml/ref/psql-ref.sgml

Lines changed: 12 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -3698,14 +3698,15 @@ testdb=&gt; <userinput>\setenv LESS -imx4F</userinput>
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</para>
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37003700
<para>
3701-
Pipeline mode requires the use of the extended query protocol. All
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queries need to be sent using the meta-commands
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<literal>\bind</literal>, <literal>\bind_named</literal>,
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<literal>\close</literal> or <literal>\parse</literal>. While a
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pipeline is ongoing, <literal>\sendpipeline</literal> will append the
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current query buffer to the pipeline. Other meta-commands like
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<literal>\g</literal>, <literal>\gx</literal> or <literal>\gdesc</literal>
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are not allowed in pipeline mode.
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All queries executed while a pipeline is ongoing use the extended
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query protocol. Queries are appended to the pipeline when ending with
3703+
a semicolon. The meta-commands <literal>\bind</literal>,
3704+
<literal>\bind_named</literal>, <literal>\close</literal> or
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<literal>\parse</literal> can be used in an ongoing pipeline. While
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a pipeline is ongoing, <literal>\sendpipeline</literal> will append
3707+
the current query buffer to the pipeline. Other meta-commands like
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<literal>\g</literal>, <literal>\gx</literal> or
3709+
<literal>\gdesc</literal> are not allowed in pipeline mode.
37093710
</para>
37103711

37113712
<para>
@@ -3723,10 +3724,7 @@ testdb=&gt; <userinput>\setenv LESS -imx4F</userinput>
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If provided, only the first
37243725
<replaceable class="parameter">number_results</replaceable> pending
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results will be read. If not provided or <literal>0</literal>, all
3726-
pending results are read. The commands <literal>\bind</literal>,
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<literal>\bind_named</literal>, <literal>\close</literal>,
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<literal>\parse</literal> and <literal>\syncpipeline</literal>
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generate one result to get.
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pending results are read.
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</para>
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<para>
@@ -3739,6 +3737,7 @@ testdb=&gt; <userinput>\setenv LESS -imx4F</userinput>
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Example:
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<programlisting>
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\startpipeline
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SELECT * FROM pg_class;
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SELECT 1 \bind \sendpipeline
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\flushrequest
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\getresults
@@ -4513,9 +4512,7 @@ bar
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<term><varname>PIPELINE_COMMAND_COUNT</varname></term>
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<listitem>
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<para>
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The number of commands generated by <literal>\bind</literal>,
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<literal>\bind_named</literal>, <literal>\close</literal> or
4518-
<literal>\parse</literal> queued in an ongoing pipeline.
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The number of commands queued in an ongoing pipeline.
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</para>
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</listitem>
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</varlistentry>

‎src/bin/psql/command.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3282,6 +3282,13 @@ exec_command_watch(PsqlScanState scan_state, bool active_branch,
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int iter = 0;
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int min_rows = 0;
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3285+
if (PQpipelineStatus(pset.db) != PQ_PIPELINE_OFF)
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{
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pg_log_error("\\watch not allowed in pipeline mode");
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clean_extended_state();
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success = false;
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}
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/*
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* Parse arguments. We allow either an unlabeled interval or
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* "name=value", where name is from the set ('i', 'interval', 'c',

‎src/bin/psql/common.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1668,7 +1668,15 @@ ExecQueryAndProcessResults(const char *query,
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}
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break;
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case PSQL_SEND_QUERY:
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success = PQsendQuery(pset.db, query);
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if (PQpipelineStatus(pset.db) != PQ_PIPELINE_OFF)
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{
1673+
success = PQsendQueryParams(pset.db, query,
1674+
0, NULL, NULL, NULL, NULL, 0);
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if (success)
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pset.piped_commands++;
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}
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else
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success = PQsendQuery(pset.db, query);
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break;
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}
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