1 /*-------------------------------------------------------------------------
2 *
3 * partcache.c
4 * Support routines for manipulating partition information cached in
5 * relcache
6 *
7 * Portions Copyright (c) 1996-2021, 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"
24 #include "catalog/pg_partitioned_table.h"
25 #include "miscadmin.h"
26 #include "nodes/makefuncs.h"
27 #include "nodes/nodeFuncs.h"
28 #include "optimizer/optimizer.h"
29 #include "partitioning/partbounds.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);
41 static List *generate_partition_qual(Relation rel);
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 */
53 PartitionKey
RelationGetPartitionKey(Relation rel)54 RelationGetPartitionKey(Relation rel)
55 {
56 if (rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
57 return NULL;
58
59 if (unlikely(rel->rd_partkey == NULL))
60 RelationBuildPartitionKey(rel);
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
RelationBuildPartitionKey(Relation relation)81 RelationBuildPartitionKey(Relation relation)
82 {
83 Form_pg_partitioned_table form;
84 HeapTuple tuple;
85 bool isnull;
86 int i;
87 PartitionKey key;
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,
98 ObjectIdGetDatum(RelationGetRelid(relation)));
99
100 if (!HeapTupleIsValid(tuple))
101 elog(ERROR, "cache lookup failed for partition key of relation %u",
102 RelationGetRelid(relation));
103
104 partkeycxt = AllocSetContextCreate(CurTransactionContext,
105 "partition key",
106 ALLOCSET_SMALL_SIZES);
107 MemoryContextCopyAndSetIdentifier(partkeycxt,
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) ?
185 HASHEXTENDED_PROC : BTORDER_PROC;
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),
217 (key->strategy == PARTITION_STRATEGY_HASH) ?
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 }
247 get_typlenbyvalalign(key->parttypid[i],
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 */
265 MemoryContextSetParent(partkeycxt, CacheMemoryContext);
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 *
RelationGetPartitionQual(Relation rel)276 RelationGetPartitionQual(Relation rel)
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 *
get_partition_qual_relid(Oid relid)298 get_partition_qual_relid(Oid relid)
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 *
generate_partition_qual(Relation rel)336 generate_partition_qual(Relation rel)
337 {
338 HeapTuple tuple;
339 MemoryContext oldcxt;
340 Datum boundDatum;
341 bool isnull;
342 List *my_qual = NIL,
343 *result = NIL;
344 Oid parentrelid;
345 Relation parent;
346
347 /* Guard against stack overflow due to overly deep partition tree */
348 check_stack_depth();
349
350 /* If we already cached the result, just return a copy */
351 if (rel->rd_partcheckvalid)
352 return copyObject(rel->rd_partcheck);
353
354 /*
355 * Grab at least an AccessShareLock on the parent table. Must do this
356 * even if the partition has been partially detached, because transactions
357 * concurrent with the detach might still be trying to use a partition
358 * descriptor that includes it.
359 */
360 parentrelid = get_partition_parent(RelationGetRelid(rel), true);
361 parent = relation_open(parentrelid, AccessShareLock);
362
363 /* Get pg_class.relpartbound */
364 tuple = SearchSysCache1(RELOID, RelationGetRelid(rel));
365 if (!HeapTupleIsValid(tuple))
366 elog(ERROR, "cache lookup failed for relation %u",
367 RelationGetRelid(rel));
368
369 boundDatum = SysCacheGetAttr(RELOID, tuple,
370 Anum_pg_class_relpartbound,
371 &isnull);
372 if (!isnull)
373 {
374 PartitionBoundSpec *bound;
375
376 bound = castNode(PartitionBoundSpec,
377 stringToNode(TextDatumGetCString(boundDatum)));
378
379 my_qual = get_qual_from_partbound(rel, parent, bound);
380 }
381
382 ReleaseSysCache(tuple);
383
384 /* Add the parent's quals to the list (if any) */
385 if (parent->rd_rel->relispartition)
386 result = list_concat(generate_partition_qual(parent), my_qual);
387 else
388 result = my_qual;
389
390 /*
391 * Change Vars to have partition's attnos instead of the parent's. We do
392 * this after we concatenate the parent's quals, because we want every Var
393 * in it to bear this relation's attnos. It's safe to assume varno = 1
394 * here.
395 */
396 result = map_partition_varattnos(result, 1, rel, parent);
397
398 /* Assert that we're not leaking any old data during assignments below */
399 Assert(rel->rd_partcheckcxt == NULL);
400 Assert(rel->rd_partcheck == NIL);
401
402 /*
403 * Save a copy in the relcache. The order of these operations is fairly
404 * critical to avoid memory leaks and ensure that we don't leave a corrupt
405 * relcache entry if we fail partway through copyObject.
406 *
407 * If, as is definitely possible, the partcheck list is NIL, then we do
408 * not need to make a context to hold it.
409 */
410 if (result != NIL)
411 {
412 rel->rd_partcheckcxt = AllocSetContextCreate(CacheMemoryContext,
413 "partition constraint",
414 ALLOCSET_SMALL_SIZES);
415 MemoryContextCopyAndSetIdentifier(rel->rd_partcheckcxt,
416 RelationGetRelationName(rel));
417 oldcxt = MemoryContextSwitchTo(rel->rd_partcheckcxt);
418 rel->rd_partcheck = copyObject(result);
419 MemoryContextSwitchTo(oldcxt);
420 }
421 else
422 rel->rd_partcheck = NIL;
423 rel->rd_partcheckvalid = true;
424
425 /* Keep the parent locked until commit */
426 relation_close(parent, NoLock);
427
428 /* Return the working copy to the caller */
429 return result;
430 }
431