<listitem>

<!--

Author: Alexander Korotkov <akorotkov@postgresql.org>

2018-07-28 [d2086b08b] Reduce path length for locking leaf B-tree pages during

Author: Peter Geoghegan <pg@bowt.ie>

2019-03-20 [dd299df81] Make heap TID a tiebreaker nbtree index column.

Author: Peter Geoghegan <pg@bowt.ie>

2019-03-20 [fab250243] Consider secondary factors during nbtree splits.

Author: Peter Geoghegan <pg@bowt.ie>

2019-03-25 [f21668f32] Add "split after new tuple" nbtree optimization.

-->

<para>

Improve speed of btree index insertions (Peter Geoghegan,

Alexander Korotkov)

Improve performance and space utilization of btree indexes with

many duplicates (Peter Geoghegan, Heikki Linnakangas)

</para>

<para>

Previously, duplicate index entries were stored unordered within

their duplicate groups. This caused overhead during index

inserts, wasted space due to excessive page splits, and reduced

<command>VACUUM</command>'s ability to recycle entire pages.

Duplicate index entries are now sorted in heap-storage order.

</para>

<para>

Indexes <application>pg_upgraded</application> from previous

releases will not have these benefits.

</para>

</listitem>

<listitem>

<!--

see commits above

-->

<para>

Allow multi-column btree indexes to be smaller (Peter Geoghegan,

Heikki Linnakangas)

</para>

<para>

Internal pages and min/max leaf page indicators now only store

index keys until the change key, rather than all indexed keys.

This also improves the locality of index access.

</para>

<para>

The new code improves the space-efficiency of page splits,

reduces locking overhead, and gives better performance for

<command>UPDATE</command>s and <command>DELETE</command>s on

indexes with many duplicates.

Indexes <application>pg_upgraded</application> from previous

releases will not have these benefits.

</para>

</listitem>

<listitem>

<!--

Author: Alexander Korotkov <akorotkov@postgresql.org>

2018-07-28 [d2086b08b] Reduce path length for locking leaf B-tree pages during

-->

<para>

Improve speed of btree index insertions by reducing locking

overhead (Alexander Korotkov)

</para>

</listitem>

<listitem>

<!--

Author: Peter Geoghegan <pg@bowt.ie>

2019-03-20 [dd299df81] Make heap TID a tiebreaker nbtree index column.

Author: Peter Geoghegan <pg@bowt.ie>

2019-03-20 [fab250243] Consider secondary factors during nbtree splits.

-->

<para>

Have new btree indexes sort duplicate index entries in heap-storage

order (Peter Geoghegan, Heikki Linnakangas)

</para>

<para>

Indexes <application>pg_upgraded</application> from previous

releases will not have this ordering.

</para>

</listitem>

<listitem>

<!--

Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>

2019-03-05 [fe280694d] Scan GiST indexes in physical order during VACUUM.

-->