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postgresql/src/backend/optimizer/util/restrictinfo.c

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/*-------------------------------------------------------------------------
*
* restrictinfo.c
* RestrictInfo node manipulation routines.
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/util/restrictinfo.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/optimizer.h"
#include "optimizer/restrictinfo.h"
static RestrictInfo *make_restrictinfo_internal(PlannerInfo *root,
Expr *clause,
Expr *orclause,
bool is_pushed_down,
bool has_clone,
bool is_clone,
bool pseudoconstant,
Index security_level,
Relids required_relids,
Relids incompatible_relids,
Relids outer_relids);
static Expr *make_sub_restrictinfos(PlannerInfo *root,
Expr *clause,
bool is_pushed_down,
bool has_clone,
bool is_clone,
bool pseudoconstant,
Index security_level,
Relids required_relids,
Relids incompatible_relids,
Relids outer_relids);
/*
* make_restrictinfo
*
* Build a RestrictInfo node containing the given subexpression.
*
* The is_pushed_down, has_clone, is_clone, and pseudoconstant flags for the
* RestrictInfo must be supplied by the caller, as well as the correct values
* for security_level, incompatible_relids, and outer_relids.
* 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
* later.
*/
RestrictInfo *
make_restrictinfo(PlannerInfo *root,
Expr *clause,
bool is_pushed_down,
bool has_clone,
bool is_clone,
bool pseudoconstant,
Index security_level,
Relids required_relids,
Relids incompatible_relids,
Relids outer_relids)
{
/*
* If it's an OR clause, build a modified copy with RestrictInfos inserted
* above each subclause of the top-level AND/OR structure.
*/
if (is_orclause(clause))
return (RestrictInfo *) make_sub_restrictinfos(root,
clause,
is_pushed_down,
has_clone,
is_clone,
pseudoconstant,
security_level,
required_relids,
incompatible_relids,
outer_relids);
/* Shouldn't be an AND clause, else AND/OR flattening messed up */
Assert(!is_andclause(clause));
return make_restrictinfo_internal(root,
clause,
NULL,
is_pushed_down,
has_clone,
is_clone,
pseudoconstant,
security_level,
required_relids,
incompatible_relids,
outer_relids);
}
/*
* make_restrictinfo_internal
*
* Common code for the main entry points and the recursive cases.
*/
static RestrictInfo *
make_restrictinfo_internal(PlannerInfo *root,
Expr *clause,
Expr *orclause,
bool is_pushed_down,
bool has_clone,
bool is_clone,
bool pseudoconstant,
Index security_level,
Relids required_relids,
Relids incompatible_relids,
Relids outer_relids)
{
RestrictInfo *restrictinfo = makeNode(RestrictInfo);
Relids baserels;
restrictinfo->clause = clause;
restrictinfo->orclause = orclause;
restrictinfo->is_pushed_down = is_pushed_down;
restrictinfo->pseudoconstant = pseudoconstant;
restrictinfo->has_clone = has_clone;
restrictinfo->is_clone = is_clone;
restrictinfo->can_join = false; /* may get set below */
restrictinfo->security_level = security_level;
restrictinfo->incompatible_relids = incompatible_relids;
restrictinfo->outer_relids = outer_relids;
/*
* If it's potentially delayable by lower-level security quals, figure out
* whether it's leakproof. We can skip testing this for level-zero quals,
* since they would never get delayed on security grounds anyway.
*/
if (security_level > 0)
restrictinfo->leakproof = !contain_leaked_vars((Node *) clause);
else
restrictinfo->leakproof = false; /* really, "don't know" */
/*
* Mark volatility as unknown. The contain_volatile_functions function
* will determine if there are any volatile functions when called for the
* first time with this RestrictInfo.
*/
restrictinfo->has_volatile = VOLATILITY_UNKNOWN;
/*
* If it's a binary opclause, set up left/right relids info. In any case
* set up the total clause relids info.
*/
if (is_opclause(clause) && list_length(((OpExpr *) clause)->args) == 2)
{
restrictinfo->left_relids = pull_varnos(root, get_leftop(clause));
restrictinfo->right_relids = pull_varnos(root, get_rightop(clause));
restrictinfo->clause_relids = bms_union(restrictinfo->left_relids,
restrictinfo->right_relids);
/*
* Does it look like a normal join clause, i.e., a binary operator
* relating expressions that come from distinct relations? If so we
* might be able to use it in a join algorithm. Note that this is a
* purely syntactic test that is made regardless of context.
*/
if (!bms_is_empty(restrictinfo->left_relids) &&
!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
{
/* Not a binary opclause, so mark left/right relid sets as empty */
restrictinfo->left_relids = NULL;
restrictinfo->right_relids = NULL;
/* and get the total relid set the hard way */
restrictinfo->clause_relids = pull_varnos(root, (Node *) clause);
}
/* required_relids defaults to clause_relids */
if (required_relids != NULL)
restrictinfo->required_relids = required_relids;
else
restrictinfo->required_relids = restrictinfo->clause_relids;
/*
* Count the number of base rels appearing in clause_relids. To do this,
* we just delete rels mentioned in root->outer_join_rels and count the
* survivors. Because we are called during deconstruct_jointree which is
* the same tree walk that populates outer_join_rels, this is a little bit
* unsafe-looking; but it should be fine because the recursion in
* deconstruct_jointree should already have visited any outer join that
* could be mentioned in this clause.
*/
baserels = bms_difference(restrictinfo->clause_relids,
root->outer_join_rels);
restrictinfo->num_base_rels = bms_num_members(baserels);
bms_free(baserels);
/*
* Label this RestrictInfo with a fresh serial number.
*/
restrictinfo->rinfo_serial = ++(root->last_rinfo_serial);
/*
* Fill in all the cacheable fields with "not yet set" markers. None of
* these will be computed until/unless needed. Note in particular that we
* don't mark a binary opclause as mergejoinable or hashjoinable here;
* that happens only if it appears in the right context (top level of a
* joinclause list).
*/
restrictinfo->parent_ec = NULL;
restrictinfo->eval_cost.startup = -1;
restrictinfo->norm_selec = -1;
restrictinfo->outer_selec = -1;
restrictinfo->mergeopfamilies = NIL;
restrictinfo->left_ec = NULL;
restrictinfo->right_ec = NULL;
restrictinfo->left_em = NULL;
restrictinfo->right_em = NULL;
restrictinfo->scansel_cache = NIL;
restrictinfo->outer_is_left = false;
restrictinfo->hashjoinoperator = InvalidOid;
restrictinfo->left_bucketsize = -1;
restrictinfo->right_bucketsize = -1;
restrictinfo->left_mcvfreq = -1;
restrictinfo->right_mcvfreq = -1;
restrictinfo->left_hasheqoperator = InvalidOid;
restrictinfo->right_hasheqoperator = InvalidOid;
return restrictinfo;
}
/*
* Recursively insert sub-RestrictInfo nodes into a boolean expression.
*
* We put RestrictInfos above simple (non-AND/OR) clauses and above
* sub-OR clauses, but not above sub-AND clauses, because there's no need.
* This may seem odd but it is closely related to the fact that we use
* implicit-AND lists at top level of RestrictInfo lists. Only ORs and
* simple clauses are valid RestrictInfos.
*
* The same is_pushed_down, has_clone, is_clone, and pseudoconstant flag
* values can be applied to all RestrictInfo nodes in the result. Likewise
* for security_level, incompatible_relids, and outer_relids.
*
* 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(PlannerInfo *root,
Expr *clause,
bool is_pushed_down,
bool has_clone,
bool is_clone,
bool pseudoconstant,
Index security_level,
Relids required_relids,
Relids incompatible_relids,
Relids outer_relids)
{
if (is_orclause(clause))
{
List *orlist = NIL;
ListCell *temp;
foreach(temp, ((BoolExpr *) clause)->args)
orlist = lappend(orlist,
make_sub_restrictinfos(root,
lfirst(temp),
is_pushed_down,
has_clone,
is_clone,
pseudoconstant,
security_level,
NULL,
incompatible_relids,
outer_relids));
return (Expr *) make_restrictinfo_internal(root,
clause,
make_orclause(orlist),
is_pushed_down,
has_clone,
is_clone,
pseudoconstant,
security_level,
required_relids,
incompatible_relids,
outer_relids);
}
else if (is_andclause(clause))
{
List *andlist = NIL;
ListCell *temp;
foreach(temp, ((BoolExpr *) clause)->args)
andlist = lappend(andlist,
make_sub_restrictinfos(root,
lfirst(temp),
is_pushed_down,
has_clone,
is_clone,
pseudoconstant,
security_level,
required_relids,
incompatible_relids,
outer_relids));
return make_andclause(andlist);
}
else
return (Expr *) make_restrictinfo_internal(root,
clause,
NULL,
is_pushed_down,
has_clone,
is_clone,
pseudoconstant,
security_level,
required_relids,
incompatible_relids,
outer_relids);
}
/*
* commute_restrictinfo
*
* Given a RestrictInfo containing a binary opclause, produce a RestrictInfo
* representing the commutation of that clause. The caller must pass the
* OID of the commutator operator (which it's presumably looked up, else
* it would not know this is valid).
*
* Beware that the result shares sub-structure with the given RestrictInfo.
* That's okay for the intended usage with derived index quals, but might
* be hazardous if the source is subject to change. Also notice that we
* assume without checking that the commutator op is a member of the same
* btree and hash opclasses as the original op.
*/
RestrictInfo *
commute_restrictinfo(RestrictInfo *rinfo, Oid comm_op)
{
RestrictInfo *result;
OpExpr *newclause;
OpExpr *clause = castNode(OpExpr, rinfo->clause);
Assert(list_length(clause->args) == 2);
/* flat-copy all the fields of clause ... */
newclause = makeNode(OpExpr);
memcpy(newclause, clause, sizeof(OpExpr));
/* ... and adjust those we need to change to commute it */
newclause->opno = comm_op;
newclause->opfuncid = InvalidOid;
newclause->args = list_make2(lsecond(clause->args),
linitial(clause->args));
/* likewise, flat-copy all the fields of rinfo ... */
result = makeNode(RestrictInfo);
memcpy(result, rinfo, sizeof(RestrictInfo));
/*
* ... and adjust those we need to change. Note in particular that we can
* preserve any cached selectivity or cost estimates, since those ought to
* be the same for the new clause. Likewise we can keep the source's
* parent_ec. It's also important that we keep the same rinfo_serial.
*/
result->clause = (Expr *) newclause;
result->left_relids = rinfo->right_relids;
result->right_relids = rinfo->left_relids;
Assert(result->orclause == NULL);
result->left_ec = rinfo->right_ec;
result->right_ec = rinfo->left_ec;
result->left_em = rinfo->right_em;
result->right_em = rinfo->left_em;
result->scansel_cache = NIL; /* not worth updating this */
if (rinfo->hashjoinoperator == clause->opno)
result->hashjoinoperator = comm_op;
else
result->hashjoinoperator = InvalidOid;
result->left_bucketsize = rinfo->right_bucketsize;
result->right_bucketsize = rinfo->left_bucketsize;
result->left_mcvfreq = rinfo->right_mcvfreq;
result->right_mcvfreq = rinfo->left_mcvfreq;
result->left_hasheqoperator = InvalidOid;
result->right_hasheqoperator = InvalidOid;
return result;
}
/*
* restriction_is_or_clause
*
* Returns t iff the restrictinfo node contains an 'or' clause.
*/
bool
restriction_is_or_clause(RestrictInfo *restrictinfo)
{
if (restrictinfo->orclause != NULL)
return true;
else
return false;
}
/*
* restriction_is_securely_promotable
*
* Returns true if it's okay to evaluate this clause "early", that is before
* other restriction clauses attached to the specified relation.
*/
bool
restriction_is_securely_promotable(RestrictInfo *restrictinfo,
RelOptInfo *rel)
{
/*
* It's okay if there are no baserestrictinfo clauses for the rel that
* would need to go before this one, *or* if this one is leakproof.
*/
if (restrictinfo->security_level <= rel->baserestrict_min_security ||
restrictinfo->leakproof)
return true;
else
return false;
}
/*
* Detect whether a RestrictInfo's clause is constant TRUE (note that it's
* surely of type boolean). No such WHERE clause could survive qual
* canonicalization, but equivclass.c may generate such RestrictInfos for
* reasons discussed therein. We should drop them again when creating
* the finished plan, which is handled by the next few functions.
*/
static inline bool
rinfo_is_constant_true(RestrictInfo *rinfo)
{
return IsA(rinfo->clause, Const) &&
!((Const *) rinfo->clause)->constisnull &&
DatumGetBool(((Const *) rinfo->clause)->constvalue);
}
/*
* 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 *l;
foreach(l, restrictinfo_list)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
Assert(!rinfo->pseudoconstant);
Assert(!rinfo_is_constant_true(rinfo));
result = lappend(result, rinfo->clause);
}
return result;
}
/*
* extract_actual_clauses
*
* Extract bare clauses from 'restrictinfo_list', returning either the
* regular ones or the pseudoconstant ones per 'pseudoconstant'.
* Constant-TRUE clauses are dropped in any case.
*/
List *
extract_actual_clauses(List *restrictinfo_list,
bool pseudoconstant)
{
List *result = NIL;
ListCell *l;
foreach(l, restrictinfo_list)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
if (rinfo->pseudoconstant == pseudoconstant &&
!rinfo_is_constant_true(rinfo))
result = lappend(result, rinfo->clause);
}
return result;
}
/*
* extract_actual_join_clauses
*
* Extract bare clauses from 'restrictinfo_list', separating those that
* semantically match the join level from those that were pushed down.
* Pseudoconstant and constant-TRUE 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
extract_actual_join_clauses(List *restrictinfo_list,
Relids joinrelids,
List **joinquals,
List **otherquals)
{
ListCell *l;
*joinquals = NIL;
*otherquals = NIL;
foreach(l, restrictinfo_list)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
if (RINFO_IS_PUSHED_DOWN(rinfo, joinrelids))
{
if (!rinfo->pseudoconstant &&
!rinfo_is_constant_true(rinfo))
*otherquals = lappend(*otherquals, rinfo->clause);
}
else
{
/* joinquals shouldn't have been marked pseudoconstant */
Assert(!rinfo->pseudoconstant);
if (!rinfo_is_constant_true(rinfo))
*joinquals = lappend(*joinquals, rinfo->clause);
}
}
}
/*
* join_clause_is_movable_to
* Test whether a join clause is a safe candidate for parameterization
* of a scan on the specified base relation.
*
* A movable join clause is one that can safely be evaluated at a rel below
* its normal semantic level (ie, its required_relids), if the values of
* variables that it would need from other rels are provided.
*
* We insist that the clause actually reference the target relation; this
* prevents undesirable movement of degenerate join clauses, and ensures
* that there is a unique place that a clause can be moved down to.
*
* We cannot move an outer-join clause into the non-nullable side of its
* outer join, as that would change the results (rows would be suppressed
* rather than being null-extended).
*
* Also there must not be an outer join below the clause that would null the
* Vars coming from the target relation. Otherwise the clause might give
* results different from what it would give at its normal semantic level.
*
* Also, the join clause must not use any relations that have LATERAL
* references to the target relation, since we could not put such rels on
* the outer side of a nestloop with the target relation.
*
* Also, we reject is_clone versions of outer-join clauses. This has the
* effect of preventing us from generating variant parameterized paths
* that differ only in which outer joins null the parameterization rel(s).
* Generating one path from the minimally-parameterized has_clone version
* is sufficient.
*/
bool
join_clause_is_movable_to(RestrictInfo *rinfo, RelOptInfo *baserel)
{
/* Clause must physically reference target rel */
if (!bms_is_member(baserel->relid, rinfo->clause_relids))
return false;
/* Cannot move an outer-join clause into the join's outer side */
if (bms_is_member(baserel->relid, rinfo->outer_relids))
return false;
/*
* Target rel's Vars must not be nulled by any outer join. We can check
* this without groveling through the individual Vars by seeing whether
* clause_relids (which includes all such Vars' varnullingrels) includes
* any outer join that can null the target rel. You might object that
* this could reject the clause on the basis of an OJ relid that came from
* some other rel's Var. However, that would still mean that the clause
* came from above that outer join and shouldn't be pushed down; so there
* should be no false positives.
*/
if (bms_overlap(rinfo->clause_relids, baserel->nulling_relids))
return false;
/* Clause must not use any rels with LATERAL references to this rel */
if (bms_overlap(baserel->lateral_referencers, rinfo->clause_relids))
return false;
/* Ignore clones, too */
if (rinfo->is_clone)
return false;
return true;
}
/*
* join_clause_is_movable_into
* Test whether a join clause is movable and can be evaluated within
* the current join context.
*
* currentrelids: the relids of the proposed evaluation location
* current_and_outer: the union of currentrelids and the required_outer
* relids (parameterization's outer relations)
*
* The API would be a bit clearer if we passed the current relids and the
* outer relids separately and did bms_union internally; but since most
* callers need to apply this function to multiple clauses, we make the
* caller perform the union.
*
* Obviously, the clause must only refer to Vars available from the current
* relation plus the outer rels. We also check that it does reference at
* least one current Var, ensuring that the clause will be pushed down to
* a unique place in a parameterized join tree. And we check that we're
* not pushing the clause into its outer-join outer side.
*
* We used to need to check that we're not pushing the clause into a lower
* outer join's inner side. However, now that clause_relids includes
* references to potentially-nulling outer joins, the other tests handle that
* concern. If the clause references any Var coming from the inside of a
* lower outer join, its clause_relids will mention that outer join, causing
* the evaluability check to fail; while if it references no such Vars, the
* references-a-target-rel check will fail.
*
* There's no check here equivalent to join_clause_is_movable_to's test on
* lateral_referencers. We assume the caller wouldn't be inquiring unless
* it'd verified that the proposed outer rels don't have lateral references
* to the current rel(s). (If we are considering join paths with the outer
* rels on the outside and the current rels on the inside, then this should
* have been checked at the outset of such consideration; see join_is_legal
* and the path parameterization checks in joinpath.c.) On the other hand,
* in join_clause_is_movable_to we are asking whether the clause could be
* moved for some valid set of outer rels, so we don't have the benefit of
* relying on prior checks for lateral-reference validity.
*
* Likewise, we don't check is_clone here: rejecting the inappropriate
* variants of a cloned clause must be handled upstream.
*
* Note: if this returns true, it means that the clause could be moved to
* this join relation, but that doesn't mean that this is the lowest join
* it could be moved to. Caller may need to make additional calls to verify
* that this doesn't succeed on either of the inputs of a proposed join.
*
* Note: get_joinrel_parampathinfo depends on the fact that if
* current_and_outer is NULL, this function will always return false
* (since one or the other of the first two tests must fail).
*/
bool
join_clause_is_movable_into(RestrictInfo *rinfo,
Relids currentrelids,
Relids current_and_outer)
{
/* Clause must be evaluable given available context */
if (!bms_is_subset(rinfo->clause_relids, current_and_outer))
return false;
/* Clause must physically reference at least one target rel */
if (!bms_overlap(currentrelids, rinfo->clause_relids))
return false;
/* Cannot move an outer-join clause into the join's outer side */
if (bms_overlap(currentrelids, rinfo->outer_relids))
return false;
return true;
}
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