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Avoid recursion when processing simple lists of AND'ed or OR'ed clauses.

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Since most of the system thinks AND and OR are N-argument expressions
anyway, let's have the grammar generate a representation of that form when
dealing with input like "x AND y AND z AND ...", rather than generating
a deeply-nested binary tree that just has to be flattened later by the
planner.  This avoids stack overflow in parse analysis when dealing with
queries having more than a few thousand such clauses; and in any case it
removes some rather unsightly inconsistencies, since some parts of parse
analysis were generating N-argument ANDs/ORs already.

It's still possible to get a stack overflow with weirdly parenthesized
input, such as "x AND (y AND (z AND ( ... )))", but such cases are not
mainstream usage.  The maximum depth of parenthesization is already
limited by Bison's stack in such cases, anyway, so that the limit is
probably fairly platform-independent.

Patch originally by Gurjeet Singh, heavily revised by me
This commit is contained in:
Tom Lane
2014-06-16 15:55:05 -04:00
parent ac608fe758
commit 2146f13408
12 changed files with 155 additions and 141 deletions
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9
src/backend/nodes/outfuncs.c
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@ -2437,15 +2437,6 @@ _outAExpr(StringInfo str, const A_Expr *node)
appendStringInfoChar(str, ' ');
WRITE_NODE_FIELD(name);
break;
case AEXPR_AND:
appendStringInfoString(str, " AND");
break;
case AEXPR_OR:
appendStringInfoString(str, " OR");
break;
case AEXPR_NOT:
appendStringInfoString(str, " NOT");
break;
case AEXPR_OP_ANY:
appendStringInfoChar(str, ' ');
WRITE_NODE_FIELD(name);