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Revise the planner's handling of "pseudoconstant" WHERE clauses, that is

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clauses containing no variables and no volatile functions.  Such a clause
can be used as a one-time qual in a gating Result plan node, to suppress
plan execution entirely when it is false.  Even when the clause is true,
putting it in a gating node wins by avoiding repeated evaluation of the
clause.  In previous PG releases, query_planner() would do this for
pseudoconstant clauses appearing at the top level of the jointree, but
there was no ability to generate a gating Result deeper in the plan tree.
To fix it, get rid of the special case in query_planner(), and instead
process pseudoconstant clauses through the normal RestrictInfo qual
distribution mechanism.  When a pseudoconstant clause is found attached to
a path node in create_plan(), pull it out and generate a gating Result at
that point.  This requires special-casing pseudoconstants in selectivity
estimation and cost_qual_eval, but on the whole it's pretty clean.
It probably even makes the planner a bit faster than before for the normal
case of no pseudoconstants, since removing pull_constant_clauses saves one
useless traversal of the qual tree.  Per gripe from Phil Frost.
This commit is contained in:
Tom Lane
2006-07-01 18:38:33 +00:00
parent 68628fc38e
commit cffd89ca73
20 changed files with 464 additions and 294 deletions
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118
src/backend/optimizer/util/restrictinfo.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.47 2006/04/07 17:05:39 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.48 2006/07/01 18:38:33 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -26,10 +26,12 @@ static RestrictInfo *make_restrictinfo_internal(Expr *clause,
Expr *orclause,
bool is_pushed_down,
bool outerjoin_delayed,
bool pseudoconstant,
Relids required_relids);
static Expr *make_sub_restrictinfos(Expr *clause,
bool is_pushed_down,
bool outerjoin_delayed,
bool pseudoconstant,
Relids required_relids);
static RestrictInfo *join_clause_is_redundant(PlannerInfo *root,
RestrictInfo *rinfo,
@@ -42,9 +44,10 @@ static RestrictInfo *join_clause_is_redundant(PlannerInfo *root,
*
* Build a RestrictInfo node containing the given subexpression.
*
* The is_pushed_down and outerjoin_delayed flags must be supplied by the
* caller. required_relids can be NULL, in which case it defaults to the
* actual clause contents (i.e., clause_relids).
* The is_pushed_down, outerjoin_delayed, and pseudoconstant flags for the
* RestrictInfo must be supplied by the caller. required_relids can be NULL,
* in which case it defaults to the actual clause contents (i.e.,
* clause_relids).
*
* We initialize fields that depend only on the given subexpression, leaving
* others that depend on context (or may never be needed at all) to be filled
@@ -54,6 +57,7 @@ RestrictInfo *
make_restrictinfo(Expr *clause,
bool is_pushed_down,
bool outerjoin_delayed,
bool pseudoconstant,
Relids required_relids)
{
/*
@@ -64,13 +68,17 @@ make_restrictinfo(Expr *clause,
return (RestrictInfo *) make_sub_restrictinfos(clause,
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
required_relids);
/* Shouldn't be an AND clause, else AND/OR flattening messed up */
Assert(!and_clause((Node *) clause));
return make_restrictinfo_internal(clause, NULL,
is_pushed_down, outerjoin_delayed,
return make_restrictinfo_internal(clause,
NULL,
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
required_relids);
}
@@ -85,7 +93,8 @@ make_restrictinfo(Expr *clause,
* RestrictInfos.
*
* The caller must pass is_pushed_down, but we assume outerjoin_delayed
* is false (no such qual should ever get into a bitmapqual).
* and pseudoconstant are false (no such qual should ever get into a
* bitmapqual).
*
* If include_predicates is true, we add any partial index predicates to
* the explicit index quals. When this is not true, we return a condition
@@ -214,6 +223,7 @@ make_restrictinfo_from_bitmapqual(Path *bitmapqual,
make_orclause(withris),
is_pushed_down,
false,
false,
NULL));
}
}
@@ -239,6 +249,7 @@ make_restrictinfo_from_bitmapqual(Path *bitmapqual,
make_restrictinfo(pred,
is_pushed_down,
false,
false,
NULL));
}
}
@@ -258,8 +269,11 @@ make_restrictinfo_from_bitmapqual(Path *bitmapqual,
* Common code for the main entry points and the recursive cases.
*/
static RestrictInfo *
make_restrictinfo_internal(Expr *clause, Expr *orclause,
bool is_pushed_down, bool outerjoin_delayed,
make_restrictinfo_internal(Expr *clause,
Expr *orclause,
bool is_pushed_down,
bool outerjoin_delayed,
bool pseudoconstant,
Relids required_relids)
{
RestrictInfo *restrictinfo = makeNode(RestrictInfo);
@@ -268,6 +282,7 @@ make_restrictinfo_internal(Expr *clause, Expr *orclause,
restrictinfo->orclause = orclause;
restrictinfo->is_pushed_down = is_pushed_down;
restrictinfo->outerjoin_delayed = outerjoin_delayed;
restrictinfo->pseudoconstant = pseudoconstant;
restrictinfo->can_join = false; /* may get set below */
/*
@@ -292,7 +307,11 @@ make_restrictinfo_internal(Expr *clause, Expr *orclause,
!bms_is_empty(restrictinfo->right_relids) &&
!bms_overlap(restrictinfo->left_relids,
restrictinfo->right_relids))
{
restrictinfo->can_join = true;
/* pseudoconstant should certainly not be true */
Assert(!restrictinfo->pseudoconstant);
}
}
else
{
@@ -346,13 +365,18 @@ make_restrictinfo_internal(Expr *clause, Expr *orclause,
* implicit-AND lists at top level of RestrictInfo lists. Only ORs and
* simple clauses are valid RestrictInfos.
*
* The same is_pushed_down, outerjoin_delayed, and pseudoconstant flag
* values can be applied to all RestrictInfo nodes in the result.
*
* The given required_relids are attached to our top-level output,
* but any OR-clause constituents are allowed to default to just the
* contained rels.
*/
static Expr *
make_sub_restrictinfos(Expr *clause,
bool is_pushed_down, bool outerjoin_delayed,
bool is_pushed_down,
bool outerjoin_delayed,
bool pseudoconstant,
Relids required_relids)
{
if (or_clause((Node *) clause))
@@ -365,11 +389,13 @@ make_sub_restrictinfos(Expr *clause,
make_sub_restrictinfos(lfirst(temp),
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
NULL));
return (Expr *) make_restrictinfo_internal(clause,
make_orclause(orlist),
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
required_relids);
}
else if (and_clause((Node *) clause))
@@ -382,6 +408,7 @@ make_sub_restrictinfos(Expr *clause,
make_sub_restrictinfos(lfirst(temp),
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
required_relids));
return make_andclause(andlist);
}
@@ -390,6 +417,7 @@ make_sub_restrictinfos(Expr *clause,
NULL,
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
required_relids);
}
@@ -411,47 +439,91 @@ restriction_is_or_clause(RestrictInfo *restrictinfo)
* get_actual_clauses
*
* Returns a list containing the bare clauses from 'restrictinfo_list'.
*
* This is only to be used in cases where none of the RestrictInfos can
* be pseudoconstant clauses (for instance, it's OK on indexqual lists).
*/
List *
get_actual_clauses(List *restrictinfo_list)
{
List *result = NIL;
ListCell *temp;
ListCell *l;
foreach(temp, restrictinfo_list)
foreach(l, restrictinfo_list)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(temp);
RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
Assert(IsA(rinfo, RestrictInfo));
Assert(!rinfo->pseudoconstant);
result = lappend(result, rinfo->clause);
}
return result;
}
/*
* get_actual_join_clauses
* extract_actual_clauses
*
* Extract clauses from 'restrictinfo_list', separating those that
* Extract bare clauses from 'restrictinfo_list', returning either the
* regular ones or the pseudoconstant ones per 'pseudoconstant'.
*/
List *
extract_actual_clauses(List *restrictinfo_list,
bool pseudoconstant)
{
List *result = NIL;
ListCell *l;
foreach(l, restrictinfo_list)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
Assert(IsA(rinfo, RestrictInfo));
if (rinfo->pseudoconstant == pseudoconstant)
result = lappend(result, rinfo->clause);
}
return result;
}
/*
* extract_actual_join_clauses
*
* Extract bare clauses from 'restrictinfo_list', separating those that
* syntactically match the join level from those that were pushed down.
* Pseudoconstant clauses are excluded from the results.
*
* This is only used at outer joins, since for plain joins we don't care
* about pushed-down-ness.
*/
void
get_actual_join_clauses(List *restrictinfo_list,
List **joinquals, List **otherquals)
extract_actual_join_clauses(List *restrictinfo_list,
List **joinquals,
List **otherquals)
{
ListCell *temp;
ListCell *l;
*joinquals = NIL;
*otherquals = NIL;
foreach(temp, restrictinfo_list)
foreach(l, restrictinfo_list)
{
RestrictInfo *clause = (RestrictInfo *) lfirst(temp);
RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
if (clause->is_pushed_down)
*otherquals = lappend(*otherquals, clause->clause);
Assert(IsA(rinfo, RestrictInfo));
if (rinfo->is_pushed_down)
{
if (!rinfo->pseudoconstant)
*otherquals = lappend(*otherquals, rinfo->clause);
}
else
*joinquals = lappend(*joinquals, clause->clause);
{
/* joinquals shouldn't have been marked pseudoconstant */
Assert(!rinfo->pseudoconstant);
*joinquals = lappend(*joinquals, rinfo->clause);
}
}
}