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Add WaitForLockers in lmgr, refactoring index.c code

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This is in support of a future REINDEX CONCURRENTLY feature.

Michael Paquier
This commit is contained in:
Alvaro Herrera
2013-09-27 11:46:33 -03:00
parent dddc91ddd3
commit 15732b34e8
4 changed files with 81 additions and 50 deletions
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30
src/backend/commands/indexcmds.c
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@ -321,7 +321,6 @@ DefineIndex(IndexStmt *stmt,
IndexInfo *indexInfo;
int numberOfAttributes;
TransactionId limitXmin;
VirtualTransactionId *old_lockholders;
VirtualTransactionId *old_snapshots;
int n_old_snapshots;
LockRelId heaprelid;
@ -652,30 +651,17 @@ DefineIndex(IndexStmt *stmt,
* for an overview of how this works)
*
* Now we must wait until no running transaction could have the table open
* with the old list of indexes. To do this, inquire which xacts
* currently would conflict with ShareLock on the table -- ie, which ones
* have a lock that permits writing the table. Then wait for each of
* these xacts to commit or abort. Note we do not need to worry about
* xacts that open the table for writing after this point; they will see
* the new index when they open it.
* with the old list of indexes. Note we do not need to worry about xacts
* that open the table for writing after this point; they will see the new
* index when they open it.
*
* Note: the reason we use actual lock acquisition here, rather than just
* checking the ProcArray and sleeping, is that deadlock is possible if
* one of the transactions in question is blocked trying to acquire an
* exclusive lock on our table. The lock code will detect deadlock and
* error out properly.
*
* Note: GetLockConflicts() never reports our own xid, hence we need not
* check for that. Also, prepared xacts are not reported, which is fine
* since they certainly aren't going to do anything more.
*/
old_lockholders = GetLockConflicts(&heaplocktag, ShareLock);
while (VirtualTransactionIdIsValid(*old_lockholders))
{
VirtualXactLock(*old_lockholders, true);
old_lockholders++;
}
WaitForLockers(heaplocktag, ShareLock);
/*
* At this moment we are sure that there are no transactions with the
@ -739,13 +725,7 @@ DefineIndex(IndexStmt *stmt,
* We once again wait until no transaction can have the table open with
* the index marked as read-only for updates.
*/
old_lockholders = GetLockConflicts(&heaplocktag, ShareLock);
while (VirtualTransactionIdIsValid(*old_lockholders))
{
VirtualXactLock(*old_lockholders, true);
old_lockholders++;
}
WaitForLockers(heaplocktag, ShareLock);
/*
* Now take the "reference snapshot" that will be used by validate_index()