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Commit1a3daa5

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Add some recursion and looping defenses in prepjointree.c.
Andrey Lepikhov demonstrated a case where we spend an unreasonableamount of time in pull_up_subqueries(). Not only is that recursingwith no explicit check for stack overrun, but the code seems notinterruptable by control-C. Let's stick a CHECK_FOR_INTERRUPTSthere, along with sprinkling some stack depth checks.An actual fix for the excessive time consumption seems a bitrisky to back-patch; but this isn't, so let's do so.Discussion:https://postgr.es/m/703c09a2-08f3-d2ec-b33d-dbecd62428b8@postgrespro.ru
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‎src/backend/optimizer/prep/prepjointree.c‎

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@@ -27,6 +27,7 @@
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#include"catalog/pg_type.h"
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#include"funcapi.h"
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#include"miscadmin.h"
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#include"nodes/makefuncs.h"
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#include"nodes/nodeFuncs.h"
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#include"optimizer/clauses.h"
@@ -315,6 +316,9 @@ static Node *
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pull_up_sublinks_jointree_recurse(PlannerInfo*root,Node*jtnode,
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Relids*relids)
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{
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/* Since this function recurses, it could be driven to stack overflow. */
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check_stack_depth();
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if (jtnode==NULL)
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{
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*relids=NULL;
@@ -812,6 +816,11 @@ pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
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JoinExpr*lowest_nulling_outer_join,
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AppendRelInfo*containing_appendrel)
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{
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/* Since this function recurses, it could be driven to stack overflow. */
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check_stack_depth();
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/* Also, since it's a bit expensive, let's check for query cancel. */
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CHECK_FOR_INTERRUPTS();
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Assert(jtnode!=NULL);
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if (IsA(jtnode,RangeTblRef))
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{
@@ -1941,6 +1950,9 @@ is_simple_union_all(Query *subquery)
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staticbool
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is_simple_union_all_recurse(Node*setOp,Query*setOpQuery,List*colTypes)
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{
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/* Since this function recurses, it could be driven to stack overflow. */
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check_stack_depth();
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if (IsA(setOp,RangeTblRef))
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{
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RangeTblRef*rtr= (RangeTblRef*)setOp;

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