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Centralize the logic for detecting misplaced aggregates, window funcs, etc.

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Formerly we relied on checking after-the-fact to see if an expression
contained aggregates, window functions, or sub-selects when it shouldn't.
This is grotty, easily forgotten (indeed, we had forgotten to teach
DefineIndex about rejecting window functions), and none too efficient
since it requires extra traversals of the parse tree.  To improve matters,
define an enum type that classifies all SQL sub-expressions, store it in
ParseState to show what kind of expression we are currently parsing, and
make transformAggregateCall, transformWindowFuncCall, and transformSubLink
check the expression type and throw error if the type indicates the
construct is disallowed.  This allows removal of a large number of ad-hoc
checks scattered around the code base.  The enum type is sufficiently
fine-grained that we can still produce error messages of at least the
same specificity as before.

Bringing these error checks together revealed that we'd been none too
consistent about phrasing of the error messages, so standardize the wording
a bit.

Also, rewrite checking of aggregate arguments so that it requires only one
traversal of the arguments, rather than up to three as before.

In passing, clean up some more comments left over from add_missing_from
support, and annotate some tests that I think are dead code now that that's
gone.  (I didn't risk actually removing said dead code, though.)
This commit is contained in:
Tom Lane
2012-08-10 11:35:33 -04:00
parent b3055ab4fb
commit eaccfded98
29 changed files with 956 additions and 785 deletions
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2
src/backend/optimizer/util/clauses.c
View File

@ -596,7 +596,7 @@ count_agg_clauses_walker(Node *node, count_agg_clauses_context *context)
bool
contain_window_function(Node *clause)
{
return checkExprHasWindowFuncs(clause);
return contain_windowfuncs(clause);
}
/*

161
src/backend/optimizer/util/var.c
View File

@ -52,12 +52,6 @@ typedef struct
int sublevels_up;
} locate_var_of_level_context;
typedef struct
{
int min_varlevel;
int sublevels_up;
} find_minimum_var_level_context;
typedef struct
{
List *varlist;
@ -81,8 +75,6 @@ static bool contain_var_clause_walker(Node *node, void *context);
static bool contain_vars_of_level_walker(Node *node, int *sublevels_up);
static bool locate_var_of_level_walker(Node *node,
locate_var_of_level_context *context);
static bool find_minimum_var_level_walker(Node *node,
find_minimum_var_level_context *context);
static bool pull_var_clause_walker(Node *node,
pull_var_clause_context *context);
static Node *flatten_join_alias_vars_mutator(Node *node,
@ -488,159 +480,6 @@ locate_var_of_level_walker(Node *node,
}
/*
* find_minimum_var_level
* Recursively scan a clause to find the lowest variable level it
* contains --- for example, zero is returned if there are any local
* variables, one if there are no local variables but there are
* one-level-up outer references, etc. Subqueries are scanned to see
* if they possess relevant outer references. (But any local variables
* within subqueries are not relevant.)
*
* -1 is returned if the clause has no variables at all.
*
* Will recurse into sublinks. Also, may be invoked directly on a Query.
*/
int
find_minimum_var_level(Node *node)
{
find_minimum_var_level_context context;
context.min_varlevel = -1; /* signifies nothing found yet */
context.sublevels_up = 0;
(void) query_or_expression_tree_walker(node,
find_minimum_var_level_walker,
(void *) &context,
0);
return context.min_varlevel;
}
static bool
find_minimum_var_level_walker(Node *node,
find_minimum_var_level_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
int varlevelsup = ((Var *) node)->varlevelsup;
/* convert levelsup to frame of reference of original query */
varlevelsup -= context->sublevels_up;
/* ignore local vars of subqueries */
if (varlevelsup >= 0)
{
if (context->min_varlevel < 0 ||
context->min_varlevel > varlevelsup)
{
context->min_varlevel = varlevelsup;
/*
* As soon as we find a local variable, we can abort the tree
* traversal, since min_varlevel is then certainly 0.
*/
if (varlevelsup == 0)
return true;
}
}
}
if (IsA(node, CurrentOfExpr))
{
int varlevelsup = 0;
/* convert levelsup to frame of reference of original query */
varlevelsup -= context->sublevels_up;
/* ignore local vars of subqueries */
if (varlevelsup >= 0)
{
if (context->min_varlevel < 0 ||
context->min_varlevel > varlevelsup)
{
context->min_varlevel = varlevelsup;
/*
* As soon as we find a local variable, we can abort the tree
* traversal, since min_varlevel is then certainly 0.
*/
if (varlevelsup == 0)
return true;
}
}
}
/*
* An Aggref must be treated like a Var of its level. Normally we'd get
* the same result from looking at the Vars in the aggregate's argument,
* but this fails in the case of a Var-less aggregate call (COUNT(*)).
*/
if (IsA(node, Aggref))
{
int agglevelsup = ((Aggref *) node)->agglevelsup;
/* convert levelsup to frame of reference of original query */
agglevelsup -= context->sublevels_up;
/* ignore local aggs of subqueries */
if (agglevelsup >= 0)
{
if (context->min_varlevel < 0 ||
context->min_varlevel > agglevelsup)
{
context->min_varlevel = agglevelsup;
/*
* As soon as we find a local aggregate, we can abort the tree
* traversal, since min_varlevel is then certainly 0.
*/
if (agglevelsup == 0)
return true;
}
}
}
/* Likewise, make sure PlaceHolderVar is treated correctly */
if (IsA(node, PlaceHolderVar))
{
int phlevelsup = ((PlaceHolderVar *) node)->phlevelsup;
/* convert levelsup to frame of reference of original query */
phlevelsup -= context->sublevels_up;
/* ignore local vars of subqueries */
if (phlevelsup >= 0)
{
if (context->min_varlevel < 0 ||
context->min_varlevel > phlevelsup)
{
context->min_varlevel = phlevelsup;
/*
* As soon as we find a local variable, we can abort the tree
* traversal, since min_varlevel is then certainly 0.
*/
if (phlevelsup == 0)
return true;
}
}
}
if (IsA(node, Query))
{
/* Recurse into subselects */
bool result;
context->sublevels_up++;
result = query_tree_walker((Query *) node,
find_minimum_var_level_walker,
(void *) context,
0);
context->sublevels_up--;
return result;
}
return expression_tree_walker(node,
find_minimum_var_level_walker,
(void *) context);
}
/*
* pull_var_clause
* Recursively pulls all Var nodes from an expression clause.