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Commit7428469

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Fix ancient memory leak in contrib/auto_explain.
The ExecutorEnd hook is invoked in a context that could be quitelong-lived, not the executor's own per-query context as I thinkwe were sort of assuming. Thus, any cruft generated while producingthe EXPLAIN output could accumulate over multiple queries. This canresult in spectacular leakage if log_nested_statements is on, andeven without that I'm surprised nobody complained before.To fix, just switch into the executor's context so that anything weallocate will be released when standard_ExecutorEnd frees the executorstate. We might as well nuke the code's retail pfree of the explainoutput string, too; that's laughably inadequate to the need.Japin Li, per report from Jeff Janes. This bug is old, soback-patch to all supported branches.Discussion:https://postgr.es/m/CAMkU=1wCVtbeRn0s9gt12KwQ7PLXovbpM8eg25SYocKW3BT4hg@mail.gmail.com
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‎contrib/auto_explain/auto_explain.c

Lines changed: 9 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -361,8 +361,15 @@ explain_ExecutorEnd(QueryDesc *queryDesc)
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{
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if (queryDesc->totaltime&&auto_explain_enabled())
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{
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MemoryContextoldcxt;
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doublemsec;
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/*
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* Make sure we operate in the per-query context, so any cruft will be
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* discarded later during ExecutorEnd.
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*/
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oldcxt=MemoryContextSwitchTo(queryDesc->estate->es_query_cxt);
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/*
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* Make sure stats accumulation is done. (Note: it's okay if several
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* levels of hook all do this.)
@@ -413,9 +420,9 @@ explain_ExecutorEnd(QueryDesc *queryDesc)
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(errmsg("duration: %.3f ms plan:\n%s",
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msec,es->str->data),
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errhidestmt(true)));
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pfree(es->str->data);
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}
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MemoryContextSwitchTo(oldcxt);
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}
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if (prev_ExecutorEnd)

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