From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
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To: | pgsql-patches(at)postgresql(dot)org |
Subject: | Phantom Command IDs |
Date: | 2006-09-28 10:37:04 |
Message-ID: | 451BA5D0.8080509@enterprisedb.com |
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Lists: | pgsql-patches |
Here's a patch that implements the Phantom Command ID idea that has been
discussed.
I didn't do anything about the system columns. We need to before
applying the patch, because the HeapTupleHeaderGetCmin/max functions
don't work properly if called outside the inserting/deleting
transaction. In fact, SELECT cmin,cmax FROM foo will cause assertion
failures if there's rows with phantom cids in the table.
I used the last free bit in t_infomask. At first I thought it wouldn't
be necessary, because you could detect that a row has a phantom command
id if both xmin and xmax are part of the current top-level transaction
(TransactionIdIsCurrentTransactionId). But that doesn't work because we
don't consider aborted subtransactions as current. Using the infomask
bit seems more robust anyway.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
Attachment | Content-Type | Size |
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phantomcid.diff | text/x-patch | 21.5 KB |
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