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Commit281a724

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committed
Rewrite DROP's dependency traversal algorithm into an honest two-pass
algorithm, replacing the original intention of a one-pass search, whichhad been hacked up over time to be partially two-pass in hopes of handlingvarious corner cases better. It still wasn't quite there, especially asregards emitting unwanted NOTICE messages. More importantly, this approachlets us fix a number of open bugs concerning concurrent DROP scenarios,because we can take locks during the first pass and avoid traversing todependent objects that were just deleted by someone else.There is more that can be done here, but I'll go ahead and commit thebase patch before working on the options.
1 parentcc87402 commit281a724

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15 files changed

+747
-656
lines changed

15 files changed

+747
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‎src/backend/access/index/genam.c

Lines changed: 42 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/index/genam.c,v 1.68 2008/04/13 19:18:14 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/index/genam.c,v 1.69 2008/06/08 22:41:04 tgl Exp $
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*
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* NOTES
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* many of the old access method routines have been turned into
@@ -251,6 +251,47 @@ systable_getnext(SysScanDesc sysscan)
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returnhtup;
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}
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/*
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* systable_recheck_tuple --- recheck visibility of most-recently-fetched tuple
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*
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* This is useful to test whether an object was deleted while we waited to
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* acquire lock on it.
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*
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* Note: we don't actually *need* the tuple to be passed in, but it's a
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* good crosscheck that the caller is interested in the right tuple.
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*/
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bool
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systable_recheck_tuple(SysScanDescsysscan,HeapTupletup)
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{
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boolresult;
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if (sysscan->irel)
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{
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IndexScanDescscan=sysscan->iscan;
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Assert(tup==&scan->xs_ctup);
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Assert(BufferIsValid(scan->xs_cbuf));
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/* must hold a buffer lock to call HeapTupleSatisfiesVisibility */
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LockBuffer(scan->xs_cbuf,BUFFER_LOCK_SHARE);
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result=HeapTupleSatisfiesVisibility(tup,scan->xs_snapshot,
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scan->xs_cbuf);
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LockBuffer(scan->xs_cbuf,BUFFER_LOCK_UNLOCK);
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}
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else
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{
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HeapScanDescscan=sysscan->scan;
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Assert(tup==&scan->rs_ctup);
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Assert(BufferIsValid(scan->rs_cbuf));
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/* must hold a buffer lock to call HeapTupleSatisfiesVisibility */
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LockBuffer(scan->rs_cbuf,BUFFER_LOCK_SHARE);
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result=HeapTupleSatisfiesVisibility(tup,scan->rs_snapshot,
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scan->rs_cbuf);
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LockBuffer(scan->rs_cbuf,BUFFER_LOCK_UNLOCK);
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}
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returnresult;
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}
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/*
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* systable_endscan --- close scan, release resources
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*

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