diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/indexam.sgml | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml index f00268d5b51..ec5741df6d1 100644 --- a/doc/src/sgml/indexam.sgml +++ b/doc/src/sgml/indexam.sgml @@ -293,6 +293,7 @@ aminsert (Relation indexRelation, ItemPointer heap_tid, Relation heapRelation, IndexUniqueCheck checkUnique, + bool indexUnchanged, IndexInfo *indexInfo); </programlisting> Insert a new tuple into an existing index. The <literal>values</literal> and @@ -309,6 +310,20 @@ aminsert (Relation indexRelation, </para> <para> + The <literal>indexUnchanged</literal> boolean value gives a hint + about the nature of the tuple to be indexed. When it is true, + the tuple is a duplicate of some existing tuple in the index. The + new tuple is a logically unchanged successor MVCC tuple version. This + happens when an <command>UPDATE</command> takes place that does not + 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>. + </para> + + <para> The function's Boolean result value is significant only when <literal>checkUnique</literal> is <literal>UNIQUE_CHECK_PARTIAL</literal>. In this case a true result means the new entry is known unique, whereas |