Sets the maximum number of parallel workers that can be

started by a single utility command. Currently, the parallel

utility commands that support the use of parallel workers are

<command>CREATE INDEX</command>onlywhen building a B-tree index,

<command>CREATE INDEX</command> when building a B-tree or BRIN index,

and <command>VACUUM</command> without <literal>FULL</literal>

option. Parallel workers are taken from the pool of processes

established by <xref linkend="guc-max-worker-processes"/>, limited

leveraging multiple CPUs in order to process the table rows faster.

This feature is known as <firstterm>parallel index

build</firstterm>. For index methods that support building indexes

in parallel (currently,onlyB-tree),

in parallel (currently, B-tree and BRIN),

<varname>maintenance_work_mem</varname> specifies the maximum

amount of memory that can be used by each index build operation as

a whole, regardless of how many worker processes were started.