discussed <link linkend="using-explain-analyze">below</link>.

</para>

<para>

When using the enable/disable flags to disable plan node types, many of

the flags only discourage the use of the corresponding plan node and don't

outright disallow the planner's ability to use the plan node type. This

is by design so that the planner still maintains the ability to form a

plan for a given query. When the resulting plan contains a disabled node,

the <command>EXPLAIN</command> output will indicate this fact.

<screen>

SET enable_seqscan = off;

EXPLAIN SELECT * FROM unit;

QUERY PLAN

---------------------------------------------------------

Seq Scan on unit (cost=0.00..21.30 rows=1130 width=44)

Disabled: true

</screen>

</para>

<para>

Because the <literal>unit</literal> table has no indexes, there is no

other means to read the table data, so the sequential scan is the only

option available to the query planner.

</para>

<para>

<indexterm>

<primary>subplan</primary>