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partcache.c
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1 /*-------------------------------------------------------------------------
2  *
3  * partcache.c
4  * Support routines for manipulating partition information cached in
5  * relcache
6  *
7  * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  * IDENTIFICATION
11  * src/backend/utils/cache/partcache.c
12  *
13  *-------------------------------------------------------------------------
14 */
15 #include "postgres.h"
16 
17 #include "access/hash.h"
18 #include "access/htup_details.h"
19 #include "access/nbtree.h"
20 #include "access/relation.h"
21 #include "catalog/partition.h"
22 #include "catalog/pg_inherits.h"
23 #include "catalog/pg_opclass.h"
25 #include "miscadmin.h"
26 #include "nodes/makefuncs.h"
27 #include "nodes/nodeFuncs.h"
28 #include "optimizer/optimizer.h"
30 #include "rewrite/rewriteHandler.h"
31 #include "utils/builtins.h"
32 #include "utils/datum.h"
33 #include "utils/lsyscache.h"
34 #include "utils/memutils.h"
35 #include "utils/partcache.h"
36 #include "utils/rel.h"
37 #include "utils/syscache.h"
38 
39 
40 static void RelationBuildPartitionKey(Relation relation);
42 
43 /*
44  * RelationGetPartitionKey -- get partition key, if relation is partitioned
45  *
46  * Note: partition keys are not allowed to change after the partitioned rel
47  * is created. RelationClearRelation knows this and preserves rd_partkey
48  * across relcache rebuilds, as long as the relation is open. Therefore,
49  * even though we hand back a direct pointer into the relcache entry, it's
50  * safe for callers to continue to use that pointer as long as they hold
51  * the relation open.
52  */
55 {
56  if (rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
57  return NULL;
58 
59  if (unlikely(rel->rd_partkey == NULL))
61 
62  return rel->rd_partkey;
63 }
64 
65 /*
66  * RelationBuildPartitionKey
67  * Build partition key data of relation, and attach to relcache
68  *
69  * Partitioning key data is a complex structure; to avoid complicated logic to
70  * free individual elements whenever the relcache entry is flushed, we give it
71  * its own memory context, a child of CacheMemoryContext, which can easily be
72  * deleted on its own. To avoid leaking memory in that context in case of an
73  * error partway through this function, the context is initially created as a
74  * child of CurTransactionContext and only re-parented to CacheMemoryContext
75  * at the end, when no further errors are possible. Also, we don't make this
76  * context the current context except in very brief code sections, out of fear
77  * that some of our callees allocate memory on their own which would be leaked
78  * permanently.
79  */
80 static void
82 {
84  HeapTuple tuple;
85  bool isnull;
86  int i;
88  AttrNumber *attrs;
89  oidvector *opclass;
90  oidvector *collation;
91  ListCell *partexprs_item;
92  Datum datum;
93  MemoryContext partkeycxt,
94  oldcxt;
95  int16 procnum;
96 
97  tuple = SearchSysCache1(PARTRELID,
99 
100  if (!HeapTupleIsValid(tuple))
101  elog(ERROR, "cache lookup failed for partition key of relation %u",
102  RelationGetRelid(relation));
103 
105  "partition key",
108  RelationGetRelationName(relation));
109 
110  key = (PartitionKey) MemoryContextAllocZero(partkeycxt,
111  sizeof(PartitionKeyData));
112 
113  /* Fixed-length attributes */
114  form = (Form_pg_partitioned_table) GETSTRUCT(tuple);
115  key->strategy = form->partstrat;
116  key->partnatts = form->partnatts;
117 
118  /*
119  * We can rely on the first variable-length attribute being mapped to the
120  * relevant field of the catalog's C struct, because all previous
121  * attributes are non-nullable and fixed-length.
122  */
123  attrs = form->partattrs.values;
124 
125  /* But use the hard way to retrieve further variable-length attributes */
126  /* Operator class */
127  datum = SysCacheGetAttr(PARTRELID, tuple,
128  Anum_pg_partitioned_table_partclass, &isnull);
129  Assert(!isnull);
130  opclass = (oidvector *) DatumGetPointer(datum);
131 
132  /* Collation */
133  datum = SysCacheGetAttr(PARTRELID, tuple,
134  Anum_pg_partitioned_table_partcollation, &isnull);
135  Assert(!isnull);
136  collation = (oidvector *) DatumGetPointer(datum);
137 
138  /* Expressions */
139  datum = SysCacheGetAttr(PARTRELID, tuple,
140  Anum_pg_partitioned_table_partexprs, &isnull);
141  if (!isnull)
142  {
143  char *exprString;
144  Node *expr;
145 
146  exprString = TextDatumGetCString(datum);
147  expr = stringToNode(exprString);
148  pfree(exprString);
149 
150  /*
151  * Run the expressions through const-simplification since the planner
152  * will be comparing them to similarly-processed qual clause operands,
153  * and may fail to detect valid matches without this step; fix
154  * opfuncids while at it. We don't need to bother with
155  * canonicalize_qual() though, because partition expressions should be
156  * in canonical form already (ie, no need for OR-merging or constant
157  * elimination).
158  */
159  expr = eval_const_expressions(NULL, expr);
160  fix_opfuncids(expr);
161 
162  oldcxt = MemoryContextSwitchTo(partkeycxt);
163  key->partexprs = (List *) copyObject(expr);
164  MemoryContextSwitchTo(oldcxt);
165  }
166 
167  /* Allocate assorted arrays in the partkeycxt, which we'll fill below */
168  oldcxt = MemoryContextSwitchTo(partkeycxt);
169  key->partattrs = (AttrNumber *) palloc0(key->partnatts * sizeof(AttrNumber));
170  key->partopfamily = (Oid *) palloc0(key->partnatts * sizeof(Oid));
171  key->partopcintype = (Oid *) palloc0(key->partnatts * sizeof(Oid));
172  key->partsupfunc = (FmgrInfo *) palloc0(key->partnatts * sizeof(FmgrInfo));
173 
174  key->partcollation = (Oid *) palloc0(key->partnatts * sizeof(Oid));
175  key->parttypid = (Oid *) palloc0(key->partnatts * sizeof(Oid));
176  key->parttypmod = (int32 *) palloc0(key->partnatts * sizeof(int32));
177  key->parttyplen = (int16 *) palloc0(key->partnatts * sizeof(int16));
178  key->parttypbyval = (bool *) palloc0(key->partnatts * sizeof(bool));
179  key->parttypalign = (char *) palloc0(key->partnatts * sizeof(char));
180  key->parttypcoll = (Oid *) palloc0(key->partnatts * sizeof(Oid));
181  MemoryContextSwitchTo(oldcxt);
182 
183  /* determine support function number to search for */
184  procnum = (key->strategy == PARTITION_STRATEGY_HASH) ?
186 
187  /* Copy partattrs and fill other per-attribute info */
188  memcpy(key->partattrs, attrs, key->partnatts * sizeof(int16));
189  partexprs_item = list_head(key->partexprs);
190  for (i = 0; i < key->partnatts; i++)
191  {
192  AttrNumber attno = key->partattrs[i];
193  HeapTuple opclasstup;
194  Form_pg_opclass opclassform;
195  Oid funcid;
196 
197  /* Collect opfamily information */
198  opclasstup = SearchSysCache1(CLAOID,
199  ObjectIdGetDatum(opclass->values[i]));
200  if (!HeapTupleIsValid(opclasstup))
201  elog(ERROR, "cache lookup failed for opclass %u", opclass->values[i]);
202 
203  opclassform = (Form_pg_opclass) GETSTRUCT(opclasstup);
204  key->partopfamily[i] = opclassform->opcfamily;
205  key->partopcintype[i] = opclassform->opcintype;
206 
207  /* Get a support function for the specified opfamily and datatypes */
208  funcid = get_opfamily_proc(opclassform->opcfamily,
209  opclassform->opcintype,
210  opclassform->opcintype,
211  procnum);
212  if (!OidIsValid(funcid))
213  ereport(ERROR,
214  (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
215  errmsg("operator class \"%s\" of access method %s is missing support function %d for type %s",
216  NameStr(opclassform->opcname),
218  "hash" : "btree",
219  procnum,
220  format_type_be(opclassform->opcintype))));
221 
222  fmgr_info_cxt(funcid, &key->partsupfunc[i], partkeycxt);
223 
224  /* Collation */
225  key->partcollation[i] = collation->values[i];
226 
227  /* Collect type information */
228  if (attno != 0)
229  {
230  Form_pg_attribute att = TupleDescAttr(relation->rd_att, attno - 1);
231 
232  key->parttypid[i] = att->atttypid;
233  key->parttypmod[i] = att->atttypmod;
234  key->parttypcoll[i] = att->attcollation;
235  }
236  else
237  {
238  if (partexprs_item == NULL)
239  elog(ERROR, "wrong number of partition key expressions");
240 
241  key->parttypid[i] = exprType(lfirst(partexprs_item));
242  key->parttypmod[i] = exprTypmod(lfirst(partexprs_item));
243  key->parttypcoll[i] = exprCollation(lfirst(partexprs_item));
244 
245  partexprs_item = lnext(key->partexprs, partexprs_item);
246  }
248  &key->parttyplen[i],
249  &key->parttypbyval[i],
250  &key->parttypalign[i]);
251 
252  ReleaseSysCache(opclasstup);
253  }
254 
255  ReleaseSysCache(tuple);
256 
257  /* Assert that we're not leaking any old data during assignments below */
258  Assert(relation->rd_partkeycxt == NULL);
259  Assert(relation->rd_partkey == NULL);
260 
261  /*
262  * Success --- reparent our context and make the relcache point to the
263  * newly constructed key
264  */
266  relation->rd_partkeycxt = partkeycxt;
267  relation->rd_partkey = key;
268 }
269 
270 /*
271  * RelationGetPartitionQual
272  *
273  * Returns a list of partition quals
274  */
275 List *
277 {
278  /* Quick exit */
279  if (!rel->rd_rel->relispartition)
280  return NIL;
281 
282  return generate_partition_qual(rel);
283 }
284 
285 /*
286  * get_partition_qual_relid
287  *
288  * Returns an expression tree describing the passed-in relation's partition
289  * constraint.
290  *
291  * If the relation is not found, or is not a partition, or there is no
292  * partition constraint, return NULL. We must guard against the first two
293  * cases because this supports a SQL function that could be passed any OID.
294  * The last case can happen even if relispartition is true, when a default
295  * partition is the only partition.
296  */
297 Expr *
299 {
300  Expr *result = NULL;
301 
302  /* Do the work only if this relation exists and is a partition. */
303  if (get_rel_relispartition(relid))
304  {
305  Relation rel = relation_open(relid, AccessShareLock);
306  List *and_args;
307 
308  and_args = generate_partition_qual(rel);
309 
310  /* Convert implicit-AND list format to boolean expression */
311  if (and_args == NIL)
312  result = NULL;
313  else if (list_length(and_args) > 1)
314  result = makeBoolExpr(AND_EXPR, and_args, -1);
315  else
316  result = linitial(and_args);
317 
318  /* Keep the lock, to allow safe deparsing against the rel by caller. */
319  relation_close(rel, NoLock);
320  }
321 
322  return result;
323 }
324 
325 /*
326  * generate_partition_qual
327  *
328  * Generate partition predicate from rel's partition bound expression. The
329  * function returns a NIL list if there is no predicate.
330  *
331  * We cache a copy of the result in the relcache entry, after constructing
332  * it using the caller's context. This approach avoids leaking any data
333  * into long-lived cache contexts, especially if we fail partway through.
334  */
335 static List *
337 {
338  HeapTuple tuple;
339  MemoryContext oldcxt;
340  Datum boundDatum;
341  bool isnull;
342  List *my_qual = NIL,
343  *result = NIL;
344  Relation parent;
345 
346  /* Guard against stack overflow due to overly deep partition tree */
348 
349  /* If we already cached the result, just return a copy */
350  if (rel->rd_partcheckvalid)
351  return copyObject(rel->rd_partcheck);
352 
353  /* Grab at least an AccessShareLock on the parent table */
356 
357  /* Get pg_class.relpartbound */
358  tuple = SearchSysCache1(RELOID, RelationGetRelid(rel));
359  if (!HeapTupleIsValid(tuple))
360  elog(ERROR, "cache lookup failed for relation %u",
361  RelationGetRelid(rel));
362 
363  boundDatum = SysCacheGetAttr(RELOID, tuple,
364  Anum_pg_class_relpartbound,
365  &isnull);
366  if (!isnull)
367  {
368  PartitionBoundSpec *bound;
369 
371  stringToNode(TextDatumGetCString(boundDatum)));
372 
373  my_qual = get_qual_from_partbound(rel, parent, bound);
374  }
375 
376  ReleaseSysCache(tuple);
377 
378  /* Add the parent's quals to the list (if any) */
379  if (parent->rd_rel->relispartition)
380  result = list_concat(generate_partition_qual(parent), my_qual);
381  else
382  result = my_qual;
383 
384  /*
385  * Change Vars to have partition's attnos instead of the parent's. We do
386  * this after we concatenate the parent's quals, because we want every Var
387  * in it to bear this relation's attnos. It's safe to assume varno = 1
388  * here.
389  */
390  result = map_partition_varattnos(result, 1, rel, parent);
391 
392  /* Assert that we're not leaking any old data during assignments below */
393  Assert(rel->rd_partcheckcxt == NULL);
394  Assert(rel->rd_partcheck == NIL);
395 
396  /*
397  * Save a copy in the relcache. The order of these operations is fairly
398  * critical to avoid memory leaks and ensure that we don't leave a corrupt
399  * relcache entry if we fail partway through copyObject.
400  *
401  * If, as is definitely possible, the partcheck list is NIL, then we do
402  * not need to make a context to hold it.
403  */
404  if (result != NIL)
405  {
407  "partition constraint",
411  oldcxt = MemoryContextSwitchTo(rel->rd_partcheckcxt);
412  rel->rd_partcheck = copyObject(result);
413  MemoryContextSwitchTo(oldcxt);
414  }
415  else
416  rel->rd_partcheck = NIL;
417  rel->rd_partcheckvalid = true;
418 
419  /* Keep the parent locked until commit */
420  relation_close(parent, NoLock);
421 
422  /* Return the working copy to the caller */
423  return result;
424 }
signed short int16
Definition: c.h:361
#define NIL
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signed int int32
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