15.15.1. Indexing Overview
Adding index support to a storage engine revolves around two
tasks: providing information to the optimizer and implementing
index-related methods. The information provided to the optimizer
helps the optimizer to make better decisions about which index
to use or even to skip using an index and instead perform a
table scan.
The indexing methods either read rows that match a key, scan a
set of rows by index order, or read information directly from
the index.
The following example shows the function calls made during an
UPDATE query that uses an index, such as
UPDATE foo SET ts = now() WHERE id = 1:
ha_foo::index_init
ha_foo::index_read
ha_foo::index_read_idx
ha_foo::rnd_next
ha_foo::update_row
In addition to index reading methods, your storage engine must
support the creation of new indexes and be able to keep table
indexes up to date as rows are added, modified, and removed from
tables.
