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restrictinfo.c
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1 /*-------------------------------------------------------------------------
2  *
3  * restrictinfo.c
4  * RestrictInfo node manipulation routines.
5  *
6  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  *
10  * IDENTIFICATION
11  * src/backend/optimizer/util/restrictinfo.c
12  *
13  *-------------------------------------------------------------------------
14  */
15 #include "postgres.h"
16 
17 #include "optimizer/clauses.h"
18 #include "optimizer/restrictinfo.h"
19 #include "optimizer/var.h"
20 
21 
23  Expr *orclause,
24  bool is_pushed_down,
25  bool outerjoin_delayed,
26  bool pseudoconstant,
27  Index security_level,
28  Relids required_relids,
29  Relids outer_relids,
30  Relids nullable_relids);
31 static Expr *make_sub_restrictinfos(Expr *clause,
32  bool is_pushed_down,
33  bool outerjoin_delayed,
34  bool pseudoconstant,
35  Index security_level,
36  Relids required_relids,
37  Relids outer_relids,
38  Relids nullable_relids);
39 
40 
41 /*
42  * make_restrictinfo
43  *
44  * Build a RestrictInfo node containing the given subexpression.
45  *
46  * The is_pushed_down, outerjoin_delayed, and pseudoconstant flags for the
47  * RestrictInfo must be supplied by the caller, as well as the correct values
48  * for security_level, outer_relids, and nullable_relids.
49  * required_relids can be NULL, in which case it defaults to the actual clause
50  * contents (i.e., clause_relids).
51  *
52  * We initialize fields that depend only on the given subexpression, leaving
53  * others that depend on context (or may never be needed at all) to be filled
54  * later.
55  */
58  bool is_pushed_down,
59  bool outerjoin_delayed,
60  bool pseudoconstant,
61  Index security_level,
62  Relids required_relids,
63  Relids outer_relids,
64  Relids nullable_relids)
65 {
66  /*
67  * If it's an OR clause, build a modified copy with RestrictInfos inserted
68  * above each subclause of the top-level AND/OR structure.
69  */
70  if (or_clause((Node *) clause))
71  return (RestrictInfo *) make_sub_restrictinfos(clause,
72  is_pushed_down,
73  outerjoin_delayed,
74  pseudoconstant,
75  security_level,
76  required_relids,
77  outer_relids,
78  nullable_relids);
79 
80  /* Shouldn't be an AND clause, else AND/OR flattening messed up */
81  Assert(!and_clause((Node *) clause));
82 
83  return make_restrictinfo_internal(clause,
84  NULL,
85  is_pushed_down,
86  outerjoin_delayed,
87  pseudoconstant,
88  security_level,
89  required_relids,
90  outer_relids,
91  nullable_relids);
92 }
93 
94 /*
95  * make_restrictinfo_internal
96  *
97  * Common code for the main entry points and the recursive cases.
98  */
99 static RestrictInfo *
101  Expr *orclause,
102  bool is_pushed_down,
103  bool outerjoin_delayed,
104  bool pseudoconstant,
105  Index security_level,
106  Relids required_relids,
107  Relids outer_relids,
108  Relids nullable_relids)
109 {
110  RestrictInfo *restrictinfo = makeNode(RestrictInfo);
111 
112  restrictinfo->clause = clause;
113  restrictinfo->orclause = orclause;
114  restrictinfo->is_pushed_down = is_pushed_down;
115  restrictinfo->outerjoin_delayed = outerjoin_delayed;
116  restrictinfo->pseudoconstant = pseudoconstant;
117  restrictinfo->can_join = false; /* may get set below */
118  restrictinfo->security_level = security_level;
119  restrictinfo->outer_relids = outer_relids;
120  restrictinfo->nullable_relids = nullable_relids;
121 
122  /*
123  * If it's potentially delayable by lower-level security quals, figure out
124  * whether it's leakproof. We can skip testing this for level-zero quals,
125  * since they would never get delayed on security grounds anyway.
126  */
127  if (security_level > 0)
128  restrictinfo->leakproof = !contain_leaked_vars((Node *) clause);
129  else
130  restrictinfo->leakproof = false; /* really, "don't know" */
131 
132  /*
133  * If it's a binary opclause, set up left/right relids info. In any case
134  * set up the total clause relids info.
135  */
136  if (is_opclause(clause) && list_length(((OpExpr *) clause)->args) == 2)
137  {
138  restrictinfo->left_relids = pull_varnos(get_leftop(clause));
139  restrictinfo->right_relids = pull_varnos(get_rightop(clause));
140 
141  restrictinfo->clause_relids = bms_union(restrictinfo->left_relids,
142  restrictinfo->right_relids);
143 
144  /*
145  * Does it look like a normal join clause, i.e., a binary operator
146  * relating expressions that come from distinct relations? If so we
147  * might be able to use it in a join algorithm. Note that this is a
148  * purely syntactic test that is made regardless of context.
149  */
150  if (!bms_is_empty(restrictinfo->left_relids) &&
151  !bms_is_empty(restrictinfo->right_relids) &&
152  !bms_overlap(restrictinfo->left_relids,
153  restrictinfo->right_relids))
154  {
155  restrictinfo->can_join = true;
156  /* pseudoconstant should certainly not be true */
157  Assert(!restrictinfo->pseudoconstant);
158  }
159  }
160  else
161  {
162  /* Not a binary opclause, so mark left/right relid sets as empty */
163  restrictinfo->left_relids = NULL;
164  restrictinfo->right_relids = NULL;
165  /* and get the total relid set the hard way */
166  restrictinfo->clause_relids = pull_varnos((Node *) clause);
167  }
168 
169  /* required_relids defaults to clause_relids */
170  if (required_relids != NULL)
171  restrictinfo->required_relids = required_relids;
172  else
173  restrictinfo->required_relids = restrictinfo->clause_relids;
174 
175  /*
176  * Fill in all the cacheable fields with "not yet set" markers. None of
177  * these will be computed until/unless needed. Note in particular that we
178  * don't mark a binary opclause as mergejoinable or hashjoinable here;
179  * that happens only if it appears in the right context (top level of a
180  * joinclause list).
181  */
182  restrictinfo->parent_ec = NULL;
183 
184  restrictinfo->eval_cost.startup = -1;
185  restrictinfo->norm_selec = -1;
186  restrictinfo->outer_selec = -1;
187 
188  restrictinfo->mergeopfamilies = NIL;
189 
190  restrictinfo->left_ec = NULL;
191  restrictinfo->right_ec = NULL;
192  restrictinfo->left_em = NULL;
193  restrictinfo->right_em = NULL;
194  restrictinfo->scansel_cache = NIL;
195 
196  restrictinfo->outer_is_left = false;
197 
198  restrictinfo->hashjoinoperator = InvalidOid;
199 
200  restrictinfo->left_bucketsize = -1;
201  restrictinfo->right_bucketsize = -1;
202  restrictinfo->left_mcvfreq = -1;
203  restrictinfo->right_mcvfreq = -1;
204 
205  return restrictinfo;
206 }
207 
208 /*
209  * Recursively insert sub-RestrictInfo nodes into a boolean expression.
210  *
211  * We put RestrictInfos above simple (non-AND/OR) clauses and above
212  * sub-OR clauses, but not above sub-AND clauses, because there's no need.
213  * This may seem odd but it is closely related to the fact that we use
214  * implicit-AND lists at top level of RestrictInfo lists. Only ORs and
215  * simple clauses are valid RestrictInfos.
216  *
217  * The same is_pushed_down, outerjoin_delayed, and pseudoconstant flag
218  * values can be applied to all RestrictInfo nodes in the result. Likewise
219  * for security_level, outer_relids, and nullable_relids.
220  *
221  * The given required_relids are attached to our top-level output,
222  * but any OR-clause constituents are allowed to default to just the
223  * contained rels.
224  */
225 static Expr *
227  bool is_pushed_down,
228  bool outerjoin_delayed,
229  bool pseudoconstant,
230  Index security_level,
231  Relids required_relids,
232  Relids outer_relids,
233  Relids nullable_relids)
234 {
235  if (or_clause((Node *) clause))
236  {
237  List *orlist = NIL;
238  ListCell *temp;
239 
240  foreach(temp, ((BoolExpr *) clause)->args)
241  orlist = lappend(orlist,
243  is_pushed_down,
244  outerjoin_delayed,
245  pseudoconstant,
246  security_level,
247  NULL,
248  outer_relids,
249  nullable_relids));
250  return (Expr *) make_restrictinfo_internal(clause,
251  make_orclause(orlist),
252  is_pushed_down,
253  outerjoin_delayed,
254  pseudoconstant,
255  security_level,
256  required_relids,
257  outer_relids,
258  nullable_relids);
259  }
260  else if (and_clause((Node *) clause))
261  {
262  List *andlist = NIL;
263  ListCell *temp;
264 
265  foreach(temp, ((BoolExpr *) clause)->args)
266  andlist = lappend(andlist,
268  is_pushed_down,
269  outerjoin_delayed,
270  pseudoconstant,
271  security_level,
272  required_relids,
273  outer_relids,
274  nullable_relids));
275  return make_andclause(andlist);
276  }
277  else
278  return (Expr *) make_restrictinfo_internal(clause,
279  NULL,
280  is_pushed_down,
281  outerjoin_delayed,
282  pseudoconstant,
283  security_level,
284  required_relids,
285  outer_relids,
286  nullable_relids);
287 }
288 
289 /*
290  * restriction_is_or_clause
291  *
292  * Returns t iff the restrictinfo node contains an 'or' clause.
293  */
294 bool
296 {
297  if (restrictinfo->orclause != NULL)
298  return true;
299  else
300  return false;
301 }
302 
303 /*
304  * restriction_is_securely_promotable
305  *
306  * Returns true if it's okay to evaluate this clause "early", that is before
307  * other restriction clauses attached to the specified relation.
308  */
309 bool
311  RelOptInfo *rel)
312 {
313  /*
314  * It's okay if there are no baserestrictinfo clauses for the rel that
315  * would need to go before this one, *or* if this one is leakproof.
316  */
317  if (restrictinfo->security_level <= rel->baserestrict_min_security ||
318  restrictinfo->leakproof)
319  return true;
320  else
321  return false;
322 }
323 
324 /*
325  * get_actual_clauses
326  *
327  * Returns a list containing the bare clauses from 'restrictinfo_list'.
328  *
329  * This is only to be used in cases where none of the RestrictInfos can
330  * be pseudoconstant clauses (for instance, it's OK on indexqual lists).
331  */
332 List *
333 get_actual_clauses(List *restrictinfo_list)
334 {
335  List *result = NIL;
336  ListCell *l;
337 
338  foreach(l, restrictinfo_list)
339  {
341 
342  Assert(!rinfo->pseudoconstant);
343 
344  result = lappend(result, rinfo->clause);
345  }
346  return result;
347 }
348 
349 /*
350  * extract_actual_clauses
351  *
352  * Extract bare clauses from 'restrictinfo_list', returning either the
353  * regular ones or the pseudoconstant ones per 'pseudoconstant'.
354  */
355 List *
356 extract_actual_clauses(List *restrictinfo_list,
357  bool pseudoconstant)
358 {
359  List *result = NIL;
360  ListCell *l;
361 
362  foreach(l, restrictinfo_list)
363  {
365 
366  if (rinfo->pseudoconstant == pseudoconstant)
367  result = lappend(result, rinfo->clause);
368  }
369  return result;
370 }
371 
372 /*
373  * extract_actual_join_clauses
374  *
375  * Extract bare clauses from 'restrictinfo_list', separating those that
376  * syntactically match the join level from those that were pushed down.
377  * Pseudoconstant clauses are excluded from the results.
378  *
379  * This is only used at outer joins, since for plain joins we don't care
380  * about pushed-down-ness.
381  */
382 void
384  List **joinquals,
385  List **otherquals)
386 {
387  ListCell *l;
388 
389  *joinquals = NIL;
390  *otherquals = NIL;
391 
392  foreach(l, restrictinfo_list)
393  {
395 
396  if (rinfo->is_pushed_down)
397  {
398  if (!rinfo->pseudoconstant)
399  *otherquals = lappend(*otherquals, rinfo->clause);
400  }
401  else
402  {
403  /* joinquals shouldn't have been marked pseudoconstant */
404  Assert(!rinfo->pseudoconstant);
405  *joinquals = lappend(*joinquals, rinfo->clause);
406  }
407  }
408 }
409 
410 
411 /*
412  * join_clause_is_movable_to
413  * Test whether a join clause is a safe candidate for parameterization
414  * of a scan on the specified base relation.
415  *
416  * A movable join clause is one that can safely be evaluated at a rel below
417  * its normal semantic level (ie, its required_relids), if the values of
418  * variables that it would need from other rels are provided.
419  *
420  * We insist that the clause actually reference the target relation; this
421  * prevents undesirable movement of degenerate join clauses, and ensures
422  * that there is a unique place that a clause can be moved down to.
423  *
424  * We cannot move an outer-join clause into the non-nullable side of its
425  * outer join, as that would change the results (rows would be suppressed
426  * rather than being null-extended).
427  *
428  * Also there must not be an outer join below the clause that would null the
429  * Vars coming from the target relation. Otherwise the clause might give
430  * results different from what it would give at its normal semantic level.
431  *
432  * Also, the join clause must not use any relations that have LATERAL
433  * references to the target relation, since we could not put such rels on
434  * the outer side of a nestloop with the target relation.
435  */
436 bool
438 {
439  /* Clause must physically reference target rel */
440  if (!bms_is_member(baserel->relid, rinfo->clause_relids))
441  return false;
442 
443  /* Cannot move an outer-join clause into the join's outer side */
444  if (bms_is_member(baserel->relid, rinfo->outer_relids))
445  return false;
446 
447  /* Target rel must not be nullable below the clause */
448  if (bms_is_member(baserel->relid, rinfo->nullable_relids))
449  return false;
450 
451  /* Clause must not use any rels with LATERAL references to this rel */
452  if (bms_overlap(baserel->lateral_referencers, rinfo->clause_relids))
453  return false;
454 
455  return true;
456 }
457 
458 /*
459  * join_clause_is_movable_into
460  * Test whether a join clause is movable and can be evaluated within
461  * the current join context.
462  *
463  * currentrelids: the relids of the proposed evaluation location
464  * current_and_outer: the union of currentrelids and the required_outer
465  * relids (parameterization's outer relations)
466  *
467  * The API would be a bit clearer if we passed the current relids and the
468  * outer relids separately and did bms_union internally; but since most
469  * callers need to apply this function to multiple clauses, we make the
470  * caller perform the union.
471  *
472  * Obviously, the clause must only refer to Vars available from the current
473  * relation plus the outer rels. We also check that it does reference at
474  * least one current Var, ensuring that the clause will be pushed down to
475  * a unique place in a parameterized join tree. And we check that we're
476  * not pushing the clause into its outer-join outer side, nor down into
477  * a lower outer join's inner side.
478  *
479  * The check about pushing a clause down into a lower outer join's inner side
480  * is only approximate; it sometimes returns "false" when actually it would
481  * be safe to use the clause here because we're still above the outer join
482  * in question. This is okay as long as the answers at different join levels
483  * are consistent: it just means we might sometimes fail to push a clause as
484  * far down as it could safely be pushed. It's unclear whether it would be
485  * worthwhile to do this more precisely. (But if it's ever fixed to be
486  * exactly accurate, there's an Assert in get_joinrel_parampathinfo() that
487  * should be re-enabled.)
488  *
489  * There's no check here equivalent to join_clause_is_movable_to's test on
490  * lateral_referencers. We assume the caller wouldn't be inquiring unless
491  * it'd verified that the proposed outer rels don't have lateral references
492  * to the current rel(s). (If we are considering join paths with the outer
493  * rels on the outside and the current rels on the inside, then this should
494  * have been checked at the outset of such consideration; see join_is_legal
495  * and the path parameterization checks in joinpath.c.) On the other hand,
496  * in join_clause_is_movable_to we are asking whether the clause could be
497  * moved for some valid set of outer rels, so we don't have the benefit of
498  * relying on prior checks for lateral-reference validity.
499  *
500  * Note: if this returns true, it means that the clause could be moved to
501  * this join relation, but that doesn't mean that this is the lowest join
502  * it could be moved to. Caller may need to make additional calls to verify
503  * that this doesn't succeed on either of the inputs of a proposed join.
504  *
505  * Note: get_joinrel_parampathinfo depends on the fact that if
506  * current_and_outer is NULL, this function will always return false
507  * (since one or the other of the first two tests must fail).
508  */
509 bool
511  Relids currentrelids,
512  Relids current_and_outer)
513 {
514  /* Clause must be evaluable given available context */
515  if (!bms_is_subset(rinfo->clause_relids, current_and_outer))
516  return false;
517 
518  /* Clause must physically reference at least one target rel */
519  if (!bms_overlap(currentrelids, rinfo->clause_relids))
520  return false;
521 
522  /* Cannot move an outer-join clause into the join's outer side */
523  if (bms_overlap(currentrelids, rinfo->outer_relids))
524  return false;
525 
526  /*
527  * Target rel(s) must not be nullable below the clause. This is
528  * approximate, in the safe direction, because the current join might be
529  * above the join where the nulling would happen, in which case the clause
530  * would work correctly here. But we don't have enough info to be sure.
531  */
532  if (bms_overlap(currentrelids, rinfo->nullable_relids))
533  return false;
534 
535  return true;
536 }
QualCost eval_cost
Definition: relation.h:1784
#define NIL
Definition: pg_list.h:69
bool contain_leaked_vars(Node *clause)
Definition: clauses.c:1481
Index security_level
Definition: relation.h:1759
RestrictInfo * make_restrictinfo(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Index security_level, Relids required_relids, Relids outer_relids, Relids nullable_relids)
Definition: restrictinfo.c:57
Relids required_relids
Definition: relation.h:1765
void extract_actual_join_clauses(List *restrictinfo_list, List **joinquals, List **otherquals)
Definition: restrictinfo.c:383
Selectivity right_mcvfreq
Definition: relation.h:1811
bool leakproof
Definition: relation.h:1757
Expr * orclause
Definition: relation.h:1778
static RestrictInfo * make_restrictinfo_internal(Expr *clause, Expr *orclause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Index security_level, Relids required_relids, Relids outer_relids, Relids nullable_relids)
Definition: restrictinfo.c:100
Relids clause_relids
Definition: relation.h:1762
bool pseudoconstant
Definition: relation.h:1755
Definition: nodes.h:509
List * get_actual_clauses(List *restrictinfo_list)
Definition: restrictinfo.c:333
Relids left_relids
Definition: relation.h:1774
return result
Definition: formatting.c:1633
EquivalenceClass * right_ec
Definition: relation.h:1796
Index baserestrict_min_security
Definition: relation.h:587
List * mergeopfamilies
Definition: relation.h:1792
bool restriction_is_or_clause(RestrictInfo *restrictinfo)
Definition: restrictinfo.c:295
Cost startup
Definition: relation.h:45
Relids outer_relids
Definition: relation.h:1768
Selectivity norm_selec
Definition: relation.h:1785
#define is_opclause(clause)
Definition: clauses.h:20
EquivalenceMember * left_em
Definition: relation.h:1797
Node * get_leftop(const Expr *clause)
Definition: clauses.c:199
EquivalenceClass * parent_ec
Definition: relation.h:1781
bool can_join
Definition: relation.h:1753
bool bms_is_subset(const Bitmapset *a, const Bitmapset *b)
Definition: bitmapset.c:308
bool outerjoin_delayed
Definition: relation.h:1751
#define lfirst_node(type, lc)
Definition: pg_list.h:109
bool and_clause(Node *clause)
Definition: clauses.c:314
bool outer_is_left
Definition: relation.h:1802
Selectivity outer_selec
Definition: relation.h:1788
bool join_clause_is_movable_into(RestrictInfo *rinfo, Relids currentrelids, Relids current_and_outer)
Definition: restrictinfo.c:510
Relids pull_varnos(Node *node)
Definition: var.c:95
Index relid
Definition: relation.h:553
List * lappend(List *list, void *datum)
Definition: list.c:128
Relids lateral_referencers
Definition: relation.h:561
EquivalenceMember * right_em
Definition: relation.h:1798
Expr * clause
Definition: relation.h:1747
bool bms_is_empty(const Bitmapset *a)
Definition: bitmapset.c:663
Relids nullable_relids
Definition: relation.h:1771
bool or_clause(Node *clause)
Definition: clauses.c:280
unsigned int Index
Definition: c.h:359
static Expr * make_sub_restrictinfos(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Index security_level, Relids required_relids, Relids outer_relids, Relids nullable_relids)
Definition: restrictinfo.c:226
#define InvalidOid
Definition: postgres_ext.h:36
bool is_pushed_down
Definition: relation.h:1749
Selectivity left_bucketsize
Definition: relation.h:1808
#define makeNode(_type_)
Definition: nodes.h:557
Relids right_relids
Definition: relation.h:1775
#define Assert(condition)
Definition: c.h:664
#define lfirst(lc)
Definition: pg_list.h:106
bool restriction_is_securely_promotable(RestrictInfo *restrictinfo, RelOptInfo *rel)
Definition: restrictinfo.c:310
Selectivity left_mcvfreq
Definition: relation.h:1810
Bitmapset * bms_union(const Bitmapset *a, const Bitmapset *b)
Definition: bitmapset.c:218
Oid hashjoinoperator
Definition: relation.h:1805
static int list_length(const List *l)
Definition: pg_list.h:89
List * extract_actual_clauses(List *restrictinfo_list, bool pseudoconstant)
Definition: restrictinfo.c:356
Node * get_rightop(const Expr *clause)
Definition: clauses.c:216
bool join_clause_is_movable_to(RestrictInfo *rinfo, RelOptInfo *baserel)
Definition: restrictinfo.c:437
bool bms_overlap(const Bitmapset *a, const Bitmapset *b)
Definition: bitmapset.c:443
Selectivity right_bucketsize
Definition: relation.h:1809
EquivalenceClass * left_ec
Definition: relation.h:1795
Expr * make_andclause(List *andclauses)
Definition: clauses.c:327
Definition: pg_list.h:45
bool bms_is_member(int x, const Bitmapset *a)
Definition: bitmapset.c:420
Expr * make_orclause(List *orclauses)
Definition: clauses.c:293
List * scansel_cache
Definition: relation.h:1799