Cost *indexStartupCost,

Cost *indexTotalCost,

Selectivity *indexSelectivity,

double *indexCorrelation);

double *indexCorrelation,

double *indexPages);

</programlisting>

Estimate the costs of an index scan. This function is described fully

in <xref linkend="index-cost-estimation"/>, below.

Cost *indexStartupCost,

Cost *indexTotalCost,

Selectivity *indexSelectivity,

double *indexCorrelation);

double *indexCorrelation,

double *indexPages);

</programlisting>

The first three parameters are inputs:

</para>

<para>

The lastfour parameters are pass-by-reference outputs:

The lastfive parameters are pass-by-reference outputs:

<variablelist>

<varlistentry>

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><parameter>*indexPages</parameter></term>

<listitem>

<para>

Set to number of index leaf pages

</para>

</listitem>

</varlistentry>

</variablelist>

</para>

table.

</para>

<para>

The <parameter>indexPages</parameter> should be set to the number of leaf pages.

This is used to estimate the number of workers for parallel index scan.

</para>

<para>

When <parameter>loop_count</parameter> is greater than one, the returned numbers

should be averages expected for any one scan of the index.