<para>

Regular index builds permit other regular index builds on the

same table to occur in parallel, but only one concurrent index build

can occur on a table at a time. In both cases, no other types of schema

modification on the table are allowed meanwhile. Another difference

is that a regular <command>CREATE INDEX</command> command can be performed within

a transaction block, but <command>CREATE INDEX CONCURRENTLY</command> cannot.

same table to occur simultaneously, but only one concurrent index build

can occur on a table at a time. In either case, schema modification of the

table is not allowed while the index is being built. Another difference is

that a regular <command>CREATE INDEX</command> command can be performed

within a transaction block, but <command>CREATE INDEX CONCURRENTLY</command>

cannot.

</para>

</refsect2>

</refsect1>

ordering. For example, we might want to sort a complex-number data

type either by absolute value or by real part. We could do this by

defining two operator classes for the data type and then selecting

the proper class whenmaking an index. More information about

the proper class whencreating an index. More information about

operator classes is in <xref linkend="indexes-opclass"/> and in <xref

linkend="xindex"/>.

</para>

will be determined as if no index name had been specified in the

command.

If the <literal>ONLY</literal> option is specified, no recursion

is done, and the index is marked invalid

(<command>ALTER INDEX ... ATTACH PARTITION</command>turns the index

valid, once all partitions acquirethe index.) Note, however, that

any partition that is created in the future using

is done, and the index is marked invalid.

(<command>ALTER INDEX ... ATTACH PARTITION</command>marks the index

valid, once all partitions acquirematching indexes.) Note, however,

thatany partition that is created in the future using

<command>CREATE TABLE ... PARTITION OF</command> will automatically

contain the index regardless of whether this option was specified.

have a matching index, regardless of whether <literal>ONLY</literal> is

specified.

</para>

<para>