From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
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To: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Index-only-scans, indexam API changes |
Date: | 2009-07-13 07:19:02 |
Message-ID: | 4A5ADFE6.6060507@enterprisedb.com |
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Lists: | pgsql-hackers |
At the moment, amgettuple only returns pointers to heap tuples. There is
no way to return data from the index tuples. That needs to be changed to
support index-only scans.
I propose that we split index_getnext into two steps: fetching the next
match from the index (index_next()), and fetching the corresponding heap
tuple (index_fetch()). Patch attached. There is still a shorthand
index_getnext() that is compatible with the old function, but it now
just calls index_next()+index_fetch().
The new index_fetch() function can only fetch one match from a HOT
chain. That greatly simplifies the code in indexam.c. The only caller
needing to fetch more than one tuple from a HOT chain (= using
SnapshotAny) is CLUSTER, so I moved the HOT-chain following logic into
cluster.c, with small changes to heap_hot_search_buffer().
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
Attachment | Content-Type | Size |
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split-index_gettuple-1.patch | text/x-diff | 27.0 KB |
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