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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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98
src/backend/parser/parse_expr.c
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@ -41,15 +41,13 @@ bool Transform_null_equals = false;
static Node *transformExprRecurse(ParseState *pstate, Node *expr);
static Node *transformParamRef(ParseState *pstate, ParamRef *pref);
static Node *transformAExprOp(ParseState *pstate, A_Expr *a);
static Node *transformAExprAnd(ParseState *pstate, A_Expr *a);
static Node *transformAExprOr(ParseState *pstate, A_Expr *a);
static Node *transformAExprNot(ParseState *pstate, A_Expr *a);
static Node *transformAExprOpAny(ParseState *pstate, A_Expr *a);
static Node *transformAExprOpAll(ParseState *pstate, A_Expr *a);
static Node *transformAExprDistinct(ParseState *pstate, A_Expr *a);
static Node *transformAExprNullIf(ParseState *pstate, A_Expr *a);
static Node *transformAExprOf(ParseState *pstate, A_Expr *a);
static Node *transformAExprIn(ParseState *pstate, A_Expr *a);
static Node *transformBoolExpr(ParseState *pstate, BoolExpr *a);
static Node *transformFuncCall(ParseState *pstate, FuncCall *fn);
static Node *transformCaseExpr(ParseState *pstate, CaseExpr *c);
static Node *transformSubLink(ParseState *pstate, SubLink *sublink);
@ -223,15 +221,6 @@ transformExprRecurse(ParseState *pstate, Node *expr)
case AEXPR_OP:
result = transformAExprOp(pstate, a);
break;
case AEXPR_AND:
result = transformAExprAnd(pstate, a);
break;
case AEXPR_OR:
result = transformAExprOr(pstate, a);
break;
case AEXPR_NOT:
result = transformAExprNot(pstate, a);
break;
case AEXPR_OP_ANY:
result = transformAExprOpAny(pstate, a);
break;
@ -258,6 +247,10 @@ transformExprRecurse(ParseState *pstate, Node *expr)
break;
}
case T_BoolExpr:
result = transformBoolExpr(pstate, (BoolExpr *) expr);
break;
case T_FuncCall:
result = transformFuncCall(pstate, (FuncCall *) expr);
break;
@ -337,7 +330,6 @@ transformExprRecurse(ParseState *pstate, Node *expr)
case T_DistinctExpr:
case T_NullIfExpr:
case T_ScalarArrayOpExpr:
case T_BoolExpr:
case T_FieldSelect:
case T_FieldStore:
case T_RelabelType:
@ -918,46 +910,6 @@ transformAExprOp(ParseState *pstate, A_Expr *a)
return result;
}
static Node *
transformAExprAnd(ParseState *pstate, A_Expr *a)
{
Node *lexpr = transformExprRecurse(pstate, a->lexpr);
Node *rexpr = transformExprRecurse(pstate, a->rexpr);
lexpr = coerce_to_boolean(pstate, lexpr, "AND");
rexpr = coerce_to_boolean(pstate, rexpr, "AND");
return (Node *) makeBoolExpr(AND_EXPR,
list_make2(lexpr, rexpr),
a->location);
}
static Node *
transformAExprOr(ParseState *pstate, A_Expr *a)
{
Node *lexpr = transformExprRecurse(pstate, a->lexpr);
Node *rexpr = transformExprRecurse(pstate, a->rexpr);
lexpr = coerce_to_boolean(pstate, lexpr, "OR");
rexpr = coerce_to_boolean(pstate, rexpr, "OR");
return (Node *) makeBoolExpr(OR_EXPR,
list_make2(lexpr, rexpr),
a->location);
}
static Node *
transformAExprNot(ParseState *pstate, A_Expr *a)
{
Node *rexpr = transformExprRecurse(pstate, a->rexpr);
rexpr = coerce_to_boolean(pstate, rexpr, "NOT");
return (Node *) makeBoolExpr(NOT_EXPR,
list_make1(rexpr),
a->location);
}
static Node *
transformAExprOpAny(ParseState *pstate, A_Expr *a)
{
@ -1237,6 +1189,42 @@ transformAExprIn(ParseState *pstate, A_Expr *a)
return result;
}
static Node *
transformBoolExpr(ParseState *pstate, BoolExpr *a)
{
List *args = NIL;
const char *opname;
ListCell *lc;
switch (a->boolop)
{
case AND_EXPR:
opname = "AND";
break;
case OR_EXPR:
opname = "OR";
break;
case NOT_EXPR:
opname = "NOT";
break;
default:
elog(ERROR, "unrecognized boolop: %d", (int) a->boolop);
opname = NULL; /* keep compiler quiet */
break;
}
foreach(lc, a->args)
{
Node *arg = (Node *) lfirst(lc);
arg = transformExprRecurse(pstate, arg);
arg = coerce_to_boolean(pstate, arg, opname);
args = lappend(args, arg);
}
return (Node *) makeBoolExpr(a->boolop, args, a->location);
}
static Node *
transformFuncCall(ParseState *pstate, FuncCall *fn)
{
@ -2428,10 +2416,6 @@ make_row_comparison_op(ParseState *pstate, List *opname,
/*
* For = and <> cases, we just combine the pairwise operators with AND or
* OR respectively.
*
* Note: this is presently the only place where the parser generates
* BoolExpr with more than two arguments. Should be OK since the rest of
* the system thinks BoolExpr is N-argument anyway.
*/
if (rctype == ROWCOMPARE_EQ)
return (Node *) makeBoolExpr(AND_EXPR, opexprs, location);