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Postgres documentation

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Hence, the query optimizer could freely convert:

<programlisting>

box '((0,0),(1,1))' &gt;&gt;&gt; MYBOXES.description

box '((0,0),(1,1))' &gt;&gt;&gt; MYBOXES.description

</programlisting>

to

<programlisting>

MYBOXES.description &lt;&lt;&lt; box '((0,0),(1,1))'

MYBOXES.description &lt;&lt;&lt; box '((0,0),(1,1))'

</programlisting>

</para>

<para>

equal, !==.

The negator link allows the query optimizer to simplify

<programlisting>

NOT MYBOXES.description === box '((0,0),(1,1))'

NOT MYBOXES.description === box '((0,0),(1,1))'

</programlisting>

to

<programlisting>

MYBOXES.description !== box '((0,0),(1,1))'

MYBOXES.description !== box '((0,0),(1,1))'

</programlisting>

</para>

<para>

The RESTRICT and JOIN options assist the query optimizer in estimating

result sizes. If a clause of the form:

<programlisting>

MYBOXES.description &lt;&lt;&lt; box '((0,0),(1,1))'

MYBOXES.description &lt;&lt;&lt; box '((0,0),(1,1))'

</programlisting>

is present in the qualification,

then <productname>Postgres</productname> may have to

<command>CREATE FUNCTION</command>) which accepts arguments of the correct

data types and returns a floating point number. The

query optimizer simply calls this function, passing the

parameter <literal>((0,0),(1,1))</literal> and multiplies the result by the relation

parameter <literal>((0,0),(1,1))</literal> and multiplies the result by the relation

size to get the expected number of instances.

</para>

<para>

<para>

The difference between the function

<programlisting>

my_procedure_1 (MYBOXES.description, box '((0,0),(1,1))')

my_procedure_1 (MYBOXES.description, box '((0,0),(1,1))')

</programlisting>

and the operator

<programlisting>

MYBOXES.description === box '((0,0),(1,1))'

MYBOXES.description === box '((0,0),(1,1))'

</programlisting>

is that <productname>Postgres</productname>

attempts to optimize operators and can