Perform index vacuum and index cleanup phases of <command>VACUUM</command>

in parallel using <replaceable class="parameter">integer</replaceable>

background workers (for the details of each vacuum phase, please

refer to <xref linkend="vacuum-phases"/>).If the

<literal>PARALLEL</literal> option is omitted, then thenumber of workers

isdetermined based onthe number ofindexes that support parallel vacuum

operation on the relation, and is further limited by <xref

linkend="guc-max-parallel-workers-maintenance"/>.

An indexcan participate in parallel vacuum if and only if the size

of the index ismore than <xref linkend="guc-min-parallel-index-scan-size"/>.

Please notethat it is not guaranteed that the number of parallel workers

specified in<replaceable class="parameter">integer</replaceable> will

be used duringexecution. It is possible for a vacuum to run with fewer

workers thanspecified, or even with no workers at all. Only one worker

can be used perindex. So parallel workers are launched only when there

are at least<literal>2</literal> indexes in the table. Workers for

vacuum are launchedbefore the start of each phase and exit at the end of

the phase. Thesebehaviors might change in a future release. This

option can't be used withthe <literal>FULL</literal> option.

refer to <xref linkend="vacuum-phases"/>).In plain <command>VACUUM</command>

(without<literal>FULL</literal>), if the<literal>PARALLEL</literal> option

isomitted, thenthe number ofworkers is determined based on the number of

indexes on the relation that support parallel vacuum operation and is further

limited by <xreflinkend="guc-max-parallel-workers-maintenance"/>. An index

can participate in parallel vacuum if and only if the size of the index is

more than <xref linkend="guc-min-parallel-index-scan-size"/>. Please note

that it is not guaranteed that the number of parallel workers specified in

<replaceable class="parameter">integer</replaceable> will be used during

execution. It is possible for a vacuum to run with fewer workers than

specified, or even with no workers at all. Only one worker can be used per

index. So parallel workers are launched only when there are at least

<literal>2</literal> indexes in the table. Workers for vacuum are launched

before the start of each phase and exit at the end of the phase. These

behaviors might change in a future release. This option can't be used with

the <literal>FULL</literal> option.

</para>

</listitem>

</varlistentry>

boolfreeze= false;

boolfull= false;

booldisable_page_skipping= false;

boolparallel_option= false;

ListCell*lc;

params.truncate=get_vacopt_ternary_value(opt);

elseif (strcmp(opt->defname,"parallel")==0)

{

parallel_option= true;

if (opt->arg==NULL)

{

ereport(ERROR,

!(params.options& (VACOPT_FULL |VACOPT_FREEZE)));

Assert(!(params.options&VACOPT_SKIPTOAST));

if ((params.options&VACOPT_FULL)&&parallel_option)

if ((params.options&VACOPT_FULL)&&params.nworkers>0)

ereport(ERROR,

(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),

errmsg("cannot specify both FULL and PARALLEL options")));

errmsg("VACUUM FULL cannot be performed in parallel")));

^

VACUUM (PARALLEL 2, INDEX_CLEANUP FALSE) pvactst;

VACUUM (PARALLEL 2, FULL TRUE) pvactst; -- error, cannot use both PARALLEL and FULL

ERROR:cannot specify both FULL and PARALLEL options

ERROR:VACUUM FULL cannot be performed in parallel

VACUUM (PARALLEL) pvactst; -- error, cannot use PARALLEL option without parallel degree

ERROR: parallel option requires a value between 0 and 1024

LINE 1: VACUUM (PARALLEL) pvactst;

^

-- Test different combinations of parallel and full options for temporary tables

CREATE TEMPORARY TABLE tmp (a int PRIMARY KEY);

CREATE INDEX tmp_idx1 ON tmp (a);

VACUUM (PARALLEL 1) tmp; --disablesparallel vacuumoption

VACUUM (PARALLEL 1, FULL FALSE) tmp; -- parallel vacuumdisabled for temp tables

WARNING: disabling parallel option of vacuum on "tmp" --- cannot vacuum temporary tables in parallel

VACUUM (PARALLEL 0, FULL TRUE) tmp; -- can specify parallel disabled (even though that's implied by FULL)

RESET min_parallel_index_scan_size;

DROP TABLE pvactst;

-- INDEX_CLEANUP option

VACUUM (PARALLEL2, INDEX_CLEANUP FALSE) pvactst;

VACUUM (PARALLEL2, FULL TRUE) pvactst;-- error, cannot use both PARALLEL and FULL

VACUUM (PARALLEL) pvactst;-- error, cannot use PARALLEL option without parallel degree

CREATE TEMPORARY TABLE tmp (aintPRIMARY KEY);

CREATEINDEXtmp_idx1ON tmp (a);

VACUUM (PARALLEL1) tmp;-- disables parallel vacuum option

VACUUM (PARALLEL1, FULL FALSE) tmp;-- parallel vacuum disabled for temp tables

VACUUM (PARALLEL0, FULL TRUE) tmp;-- can specify parallel disabled (even though that's implied by FULL)

RESET min_parallel_index_scan_size;

DROPTABLE pvactst;