modify any columns covered by the index, but nevertheless requires a

new version in the index. The index AM may use this hint to decide

to apply bottom-up index deletion in parts of the index where many

versions of the same logical row accumulate. Note that updating a

non-key column does not affect the value of

<literal>indexUnchanged</literal>.

versions of the same logical row accumulate. Note that updating a non-key

column or a column that only appears in a partial index predicate does not

affect the value of <literal>indexUnchanged</literal>. The core code

determines each tuple's <literal>indexUnchanged</literal> value using a low

overhead approach that allows both false positives and false negatives.

Index AMs must not treat <literal>indexUnchanged</literal> as an

authoritative source of information about tuple visibility or versioning.

</para>

<para>