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SERIALIZABLE transactions are actually implemented beneath the covers with

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transaction snapshots, i.e. a snapshot registered at the beginning of
a transaction. Change variable naming and comments to reflect this reality
in preparation for a future, truly serializable mode, e.g.
Serializable Snapshot Isolation (SSI).

For the moment transaction snapshots are still used to implement
SERIALIZABLE, but hopefully not for too much longer. Patch by Kevin
Grittner and Dan Ports with review and some minor wording changes by me.
This commit is contained in:
Joe Conway
2010-09-11 18:38:58 +00:00
parent 262c71ab63
commit 5eb15c9942
11 changed files with 49 additions and 49 deletions
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6
src/backend/tcop/pquery.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/tcop/pquery.c,v 1.137 2010/02/26 02:01:02 momjian Exp $
* $PostgreSQL: pgsql/src/backend/tcop/pquery.c,v 1.138 2010/09/11 18:38:56 joe Exp $
*
*-------------------------------------------------------------------------
*/
@ -1163,8 +1163,8 @@ PortalRunUtility(Portal portal, Node *utilityStmt, bool isTopLevel,
* Set snapshot if utility stmt needs one. Most reliable way to do this
* seems to be to enumerate those that do not need one; this is a short
* list. Transaction control, LOCK, and SET must *not* set a snapshot
* since they need to be executable at the start of a serializable
* transaction without freezing a snapshot. By extension we allow SHOW
* since they need to be executable at the start of a transaction-snapshot
* mode transaction without freezing a snapshot. By extension we allow SHOW
* not to set a snapshot. The other stmts listed are just efficiency
* hacks. Beware of listing anything that can modify the database --- if,
* say, it has to update an index with expressions that invoke