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Fix oversight in previous error-reporting patch; mustn't pfree path string
[PostgreSQL.git] / src / backend / optimizer / prep / preptlist.c
blob3136410458a178ba63daff8af3d3036f1c90dd17
1 /*-------------------------------------------------------------------------
2 *
3 * preptlist.c
4 * Routines to preprocess the parse tree target list
5 *
6 * This module takes care of altering the query targetlist as needed for
7 * INSERT, UPDATE, and DELETE queries. For INSERT and UPDATE queries,
8 * the targetlist must contain an entry for each attribute of the target
9 * relation in the correct order. For both UPDATE and DELETE queries,
10 * we need a junk targetlist entry holding the CTID attribute --- the
11 * executor relies on this to find the tuple to be replaced/deleted.
12 * We may also need junk tlist entries for Vars used in the RETURNING list.
13 *
14 *
15 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
16 * Portions Copyright (c) 1994, Regents of the University of California
17 *
18 * IDENTIFICATION
19 * $PostgreSQL$
20 *
21 *-------------------------------------------------------------------------
22 */
23
24 #include "postgres.h"
25
26 #include "access/heapam.h"
27 #include "access/sysattr.h"
28 #include "catalog/pg_type.h"
29 #include "nodes/makefuncs.h"
30 #include "optimizer/prep.h"
31 #include "optimizer/subselect.h"
32 #include "optimizer/tlist.h"
33 #include "optimizer/var.h"
34 #include "parser/analyze.h"
35 #include "parser/parsetree.h"
36 #include "parser/parse_coerce.h"
37 #include "utils/rel.h"
38
39
40 static List *expand_targetlist(List *tlist, int command_type,
41 Index result_relation, List *range_table);
42
43
44 /*
45 * preprocess_targetlist
46 * Driver for preprocessing the parse tree targetlist.
47 *
48 * Returns the new targetlist.
49 */
50 List *
51 preprocess_targetlist(PlannerInfo *root, List *tlist)
52 {
53 Query *parse = root->parse;
54 int result_relation = parse->resultRelation;
55 List *range_table = parse->rtable;
56 CmdType command_type = parse->commandType;
57
58 /*
59 * Sanity check: if there is a result relation, it'd better be a real
60 * relation not a subquery. Else parser or rewriter messed up.
61 */
62 if (result_relation)
63 {
64 RangeTblEntry *rte = rt_fetch(result_relation, range_table);
65
66 if (rte->subquery != NULL || rte->relid == InvalidOid)
67 elog(ERROR, "subquery cannot be result relation");
68 }
69
70 /*
71 * for heap_form_tuple to work, the targetlist must match the exact order
72 * of the attributes. We also need to fill in any missing attributes. -ay
73 * 10/94
74 */
75 if (command_type == CMD_INSERT || command_type == CMD_UPDATE)
76 tlist = expand_targetlist(tlist, command_type,
77 result_relation, range_table);
78
79 /*
80 * for "update" and "delete" queries, add ctid of the result relation into
81 * the target list so that the ctid will propagate through execution and
82 * ExecutePlan() will be able to identify the right tuple to replace or
83 * delete. This extra field is marked "junk" so that it is not stored
84 * back into the tuple.
85 */
86 if (command_type == CMD_UPDATE || command_type == CMD_DELETE)
87 {
88 TargetEntry *tle;
89 Var *var;
90
91 var = makeVar(result_relation, SelfItemPointerAttributeNumber,
92 TIDOID, -1, 0);
93
94 tle = makeTargetEntry((Expr *) var,
95 list_length(tlist) + 1,
96 pstrdup("ctid"),
97 true);
98
99 /*
100 * For an UPDATE, expand_targetlist already created a fresh tlist. For
101 * DELETE, better do a listCopy so that we don't destructively modify
102 * the original tlist (is this really necessary?).
103 */
104 if (command_type == CMD_DELETE)
105 tlist = list_copy(tlist);
106
107 tlist = lappend(tlist, tle);
108 }
109
110 /*
111 * Add TID targets for rels selected FOR UPDATE/SHARE. The executor uses
112 * the TID to know which rows to lock, much as for UPDATE or DELETE.
113 */
114 if (parse->rowMarks)
115 {
116 ListCell *l;
117
118 /*
119 * We've got trouble if the FOR UPDATE/SHARE appears inside grouping,
120 * since grouping renders a reference to individual tuple CTIDs
121 * invalid. This is also checked at parse time, but that's
122 * insufficient because of rule substitution, query pullup, etc.
123 */
124 CheckSelectLocking(parse);
125
126 /*
127 * Currently the executor only supports FOR UPDATE/SHARE at top level
128 */
129 if (root->query_level > 1)
130 ereport(ERROR,
131 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
132 errmsg("SELECT FOR UPDATE/SHARE is not allowed in subqueries")));
133
134 foreach(l, parse->rowMarks)
135 {
136 RowMarkClause *rc = (RowMarkClause *) lfirst(l);
137 Var *var;
138 char *resname;
139 TargetEntry *tle;
140
141 var = makeVar(rc->rti,
142 SelfItemPointerAttributeNumber,
143 TIDOID,
144 -1,
145 0);
146
147 resname = (char *) palloc(32);
148 snprintf(resname, 32, "ctid%u", rc->rti);
149
150 tle = makeTargetEntry((Expr *) var,
151 list_length(tlist) + 1,
152 resname,
153 true);
154
155 tlist = lappend(tlist, tle);
156 }
157 }
158
159 /*
160 * If the query has a RETURNING list, add resjunk entries for any Vars
161 * used in RETURNING that belong to other relations. We need to do this
162 * to make these Vars available for the RETURNING calculation. Vars that
163 * belong to the result rel don't need to be added, because they will be
164 * made to refer to the actual heap tuple.
165 */
166 if (parse->returningList && list_length(parse->rtable) > 1)
167 {
168 List *vars;
169 ListCell *l;
170
171 vars = pull_var_clause((Node *) parse->returningList, true);
172 foreach(l, vars)
173 {
174 Var *var = (Var *) lfirst(l);
175 TargetEntry *tle;
176
177 if (IsA(var, Var) &&
178 var->varno == result_relation)
179 continue; /* don't need it */
180
181 if (tlist_member((Node *) var, tlist))
182 continue; /* already got it */
183
184 tle = makeTargetEntry((Expr *) var,
185 list_length(tlist) + 1,
186 NULL,
187 true);
188
189 tlist = lappend(tlist, tle);
190 }
191 list_free(vars);
192 }
193
194 return tlist;
195 }
196
197 /*****************************************************************************
198 *
199 * TARGETLIST EXPANSION
200 *
201 *****************************************************************************/
202
203 /*
204 * expand_targetlist
205 * Given a target list as generated by the parser and a result relation,
206 * add targetlist entries for any missing attributes, and ensure the
207 * non-junk attributes appear in proper field order.
208 *
209 * NOTE: if you are tempted to put more processing here, consider whether
210 * it shouldn't go in the rewriter's rewriteTargetList() instead.
211 */
212 static List *
213 expand_targetlist(List *tlist, int command_type,
214 Index result_relation, List *range_table)
215 {
216 List *new_tlist = NIL;
217 ListCell *tlist_item;
218 Relation rel;
219 int attrno,
220 numattrs;
221
222 tlist_item = list_head(tlist);
223
224 /*
225 * The rewriter should have already ensured that the TLEs are in correct
226 * order; but we have to insert TLEs for any missing attributes.
227 *
228 * Scan the tuple description in the relation's relcache entry to make
229 * sure we have all the user attributes in the right order. We assume
230 * that the rewriter already acquired at least AccessShareLock on the
231 * relation, so we need no lock here.
232 */
233 rel = heap_open(getrelid(result_relation, range_table), NoLock);
234
235 numattrs = RelationGetNumberOfAttributes(rel);
236
237 for (attrno = 1; attrno <= numattrs; attrno++)
238 {
239 Form_pg_attribute att_tup = rel->rd_att->attrs[attrno - 1];
240 TargetEntry *new_tle = NULL;
241
242 if (tlist_item != NULL)
243 {
244 TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
245
246 if (!old_tle->resjunk && old_tle->resno == attrno)
247 {
248 new_tle = old_tle;
249 tlist_item = lnext(tlist_item);
250 }
251 }
252
253 if (new_tle == NULL)
254 {
255 /*
256 * Didn't find a matching tlist entry, so make one.
257 *
258 * For INSERT, generate a NULL constant. (We assume the rewriter
259 * would have inserted any available default value.) Also, if the
260 * column isn't dropped, apply any domain constraints that might
261 * exist --- this is to catch domain NOT NULL.
262 *
263 * For UPDATE, generate a Var reference to the existing value of
264 * the attribute, so that it gets copied to the new tuple. But
265 * generate a NULL for dropped columns (we want to drop any old
266 * values).
267 *
268 * When generating a NULL constant for a dropped column, we label
269 * it INT4 (any other guaranteed-to-exist datatype would do as
270 * well). We can't label it with the dropped column's datatype
271 * since that might not exist anymore. It does not really matter
272 * what we claim the type is, since NULL is NULL --- its
273 * representation is datatype-independent. This could perhaps
274 * confuse code comparing the finished plan to the target
275 * relation, however.
276 */
277 Oid atttype = att_tup->atttypid;
278 int32 atttypmod = att_tup->atttypmod;
279 Node *new_expr;
280
281 switch (command_type)
282 {
283 case CMD_INSERT:
284 if (!att_tup->attisdropped)
285 {
286 new_expr = (Node *) makeConst(atttype,
287 -1,
288 att_tup->attlen,
289 (Datum) 0,
290 true, /* isnull */
291 att_tup->attbyval);
292 new_expr = coerce_to_domain(new_expr,
293 InvalidOid, -1,
294 atttype,
295 COERCE_IMPLICIT_CAST,
296 -1,
297 false,
298 false);
299 }
300 else
301 {
302 /* Insert NULL for dropped column */
303 new_expr = (Node *) makeConst(INT4OID,
304 -1,
305 sizeof(int32),
306 (Datum) 0,
307 true, /* isnull */
308 true /* byval */ );
309 }
310 break;
311 case CMD_UPDATE:
312 if (!att_tup->attisdropped)
313 {
314 new_expr = (Node *) makeVar(result_relation,
315 attrno,
316 atttype,
317 atttypmod,
318 0);
319 }
320 else
321 {
322 /* Insert NULL for dropped column */
323 new_expr = (Node *) makeConst(INT4OID,
324 -1,
325 sizeof(int32),
326 (Datum) 0,
327 true, /* isnull */
328 true /* byval */ );
329 }
330 break;
331 default:
332 elog(ERROR, "unrecognized command_type: %d",
333 (int) command_type);
334 new_expr = NULL; /* keep compiler quiet */
335 break;
336 }
337
338 new_tle = makeTargetEntry((Expr *) new_expr,
339 attrno,
340 pstrdup(NameStr(att_tup->attname)),
341 false);
342 }
343
344 new_tlist = lappend(new_tlist, new_tle);
345 }
346
347 /*
348 * The remaining tlist entries should be resjunk; append them all to the
349 * end of the new tlist, making sure they have resnos higher than the last
350 * real attribute. (Note: although the rewriter already did such
351 * renumbering, we have to do it again here in case we are doing an UPDATE
352 * in a table with dropped columns, or an inheritance child table with
353 * extra columns.)
354 */
355 while (tlist_item)
356 {
357 TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
358
359 if (!old_tle->resjunk)
360 elog(ERROR, "targetlist is not sorted correctly");
361 /* Get the resno right, but don't copy unnecessarily */
362 if (old_tle->resno != attrno)
363 {
364 old_tle = flatCopyTargetEntry(old_tle);
365 old_tle->resno = attrno;
366 }
367 new_tlist = lappend(new_tlist, old_tle);
368 attrno++;
369 tlist_item = lnext(tlist_item);
370 }
371
372 heap_close(rel, NoLock);
373
374 return new_tlist;
375 }
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