PostgreSQL Source Code: src/backend/access/common/attmap.c Source File

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attmap.c
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1/*-------------------------------------------------------------------------
2 *
3 * attmap.c
4 * Attribute mapping support.
5 *
6 * This file provides utility routines to build and manage attribute
7 * mappings by comparing input and output TupleDescs. Such mappings
8 * are typically used by DDL operating on inheritance and partition trees
9 * to do a conversion between rowtypes logically equivalent but with
10 * columns in a different order, taking into account dropped columns.
11 * They are also used by the tuple conversion routines in tupconvert.c.
12 *
13 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
14 * Portions Copyright (c) 1994, Regents of the University of California
15 *
16 *
17 * IDENTIFICATION
18 * src/backend/access/common/attmap.c
19 *
20 *-------------------------------------------------------------------------
21 */
22
23#include "postgres.h"
24
25#include "access/attmap.h"
26#include "utils/builtins.h"
27
28
29static bool check_attrmap_match(TupleDesc indesc,
30 TupleDesc outdesc,
31 AttrMap *attrMap);
32
33/*
34 * make_attrmap
35 *
36 * Utility routine to allocate an attribute map in the current memory
37 * context.
38 */
39AttrMap *
40 make_attrmap(int maplen)
41{
42 AttrMap *res;
43
44 res = (AttrMap *) palloc0(sizeof(AttrMap));
45 res->maplen = maplen;
46 res->attnums = (AttrNumber *) palloc0(sizeof(AttrNumber) * maplen);
47 return res;
48}
49
50/*
51 * free_attrmap
52 *
53 * Utility routine to release an attribute map.
54 */
55void
56 free_attrmap(AttrMap *map)
57{
58 pfree(map->attnums);
59 pfree(map);
60}
61
62/*
63 * build_attrmap_by_position
64 *
65 * Return a palloc'd bare attribute map for tuple conversion, matching input
66 * and output columns by position. Dropped columns are ignored in both input
67 * and output, marked as 0. This is normally a subroutine for
68 * convert_tuples_by_position in tupconvert.c, but it can be used standalone.
69 *
70 * Note: the errdetail messages speak of indesc as the "returned" rowtype,
71 * outdesc as the "expected" rowtype. This is okay for current uses but
72 * might need generalization in future.
73 */
74AttrMap *
75 build_attrmap_by_position(TupleDesc indesc,
76 TupleDesc outdesc,
77 const char *msg)
78{
79 AttrMap *attrMap;
80 int nincols;
81 int noutcols;
82 int n;
83 int i;
84 int j;
85 bool same;
86
87 /*
88 * The length is computed as the number of attributes of the expected
89 * rowtype as it includes dropped attributes in its count.
90 */
91 n = outdesc->natts;
92 attrMap = make_attrmap(n);
93
94 j = 0; /* j is next physical input attribute */
95 nincols = noutcols = 0; /* these count non-dropped attributes */
96 same = true;
97 for (i = 0; i < n; i++)
98 {
99 Form_pg_attribute outatt = TupleDescAttr(outdesc, i);
100
101 if (outatt->attisdropped)
102 continue; /* attrMap->attnums[i] is already 0 */
103 noutcols++;
104 for (; j < indesc->natts; j++)
105 {
106 Form_pg_attribute inatt = TupleDescAttr(indesc, j);
107
108 if (inatt->attisdropped)
109 continue;
110 nincols++;
111
112 /* Found matching column, now check type */
113 if (outatt->atttypid != inatt->atttypid ||
114 (outatt->atttypmod != inatt->atttypmod && outatt->atttypmod >= 0))
115 ereport(ERROR,
116 (errcode(ERRCODE_DATATYPE_MISMATCH),
117 errmsg_internal("%s", _(msg)),
118 errdetail("Returned type %s does not match expected type %s in column \"%s\" (position %d).",
119 format_type_with_typemod(inatt->atttypid,
120 inatt->atttypmod),
121 format_type_with_typemod(outatt->atttypid,
122 outatt->atttypmod),
123 NameStr(outatt->attname),
124 noutcols)));
125 attrMap->attnums[i] = (AttrNumber) (j + 1);
126 j++;
127 break;
128 }
129 if (attrMap->attnums[i] == 0)
130 same = false; /* we'll complain below */
131 }
132
133 /* Check for unused input columns */
134 for (; j < indesc->natts; j++)
135 {
136 if (TupleDescCompactAttr(indesc, j)->attisdropped)
137 continue;
138 nincols++;
139 same = false; /* we'll complain below */
140 }
141
142 /* Report column count mismatch using the non-dropped-column counts */
143 if (!same)
144 ereport(ERROR,
145 (errcode(ERRCODE_DATATYPE_MISMATCH),
146 errmsg_internal("%s", _(msg)),
147 errdetail("Number of returned columns (%d) does not match "
148 "expected column count (%d).",
149 nincols, noutcols)));
150
151 /* Check if the map has a one-to-one match */
152 if (check_attrmap_match(indesc, outdesc, attrMap))
153 {
154 /* Runtime conversion is not needed */
155 free_attrmap(attrMap);
156 return NULL;
157 }
158
159 return attrMap;
160}
161
162/*
163 * build_attrmap_by_name
164 *
165 * Return a palloc'd bare attribute map for tuple conversion, matching input
166 * and output columns by name. (Dropped columns are ignored in both input and
167 * output.) This is normally a subroutine for convert_tuples_by_name in
168 * tupconvert.c, but can be used standalone.
169 *
170 * If 'missing_ok' is true, a column from 'outdesc' not being present in
171 * 'indesc' is not flagged as an error; AttrMap.attnums[] entry for such an
172 * outdesc column will be 0 in that case.
173 */
174AttrMap *
175 build_attrmap_by_name(TupleDesc indesc,
176 TupleDesc outdesc,
177 bool missing_ok)
178{
179 AttrMap *attrMap;
180 int outnatts;
181 int innatts;
182 int i;
183 int nextindesc = -1;
184
185 outnatts = outdesc->natts;
186 innatts = indesc->natts;
187
188 attrMap = make_attrmap(outnatts);
189 for (i = 0; i < outnatts; i++)
190 {
191 Form_pg_attribute outatt = TupleDescAttr(outdesc, i);
192 char *attname;
193 Oid atttypid;
194 int32 atttypmod;
195 int j;
196
197 if (outatt->attisdropped)
198 continue; /* attrMap->attnums[i] is already 0 */
199 attname = NameStr(outatt->attname);
200 atttypid = outatt->atttypid;
201 atttypmod = outatt->atttypmod;
202
203 /*
204 * Now search for an attribute with the same name in the indesc. It
205 * seems likely that a partitioned table will have the attributes in
206 * the same order as the partition, so the search below is optimized
207 * for that case. It is possible that columns are dropped in one of
208 * the relations, but not the other, so we use the 'nextindesc'
209 * counter to track the starting point of the search. If the inner
210 * loop encounters dropped columns then it will have to skip over
211 * them, but it should leave 'nextindesc' at the correct position for
212 * the next outer loop.
213 */
214 for (j = 0; j < innatts; j++)
215 {
216 Form_pg_attribute inatt;
217
218 nextindesc++;
219 if (nextindesc >= innatts)
220 nextindesc = 0;
221
222 inatt = TupleDescAttr(indesc, nextindesc);
223 if (inatt->attisdropped)
224 continue;
225 if (strcmp(attname, NameStr(inatt->attname)) == 0)
226 {
227 /* Found it, check type */
228 if (atttypid != inatt->atttypid || atttypmod != inatt->atttypmod)
229 ereport(ERROR,
230 (errcode(ERRCODE_DATATYPE_MISMATCH),
231 errmsg("could not convert row type"),
232 errdetail("Attribute \"%s\" of type %s does not match corresponding attribute of type %s.",
233 attname,
234 format_type_be(outdesc->tdtypeid),
235 format_type_be(indesc->tdtypeid))));
236 attrMap->attnums[i] = inatt->attnum;
237 break;
238 }
239 }
240 if (attrMap->attnums[i] == 0 && !missing_ok)
241 ereport(ERROR,
242 (errcode(ERRCODE_DATATYPE_MISMATCH),
243 errmsg("could not convert row type"),
244 errdetail("Attribute \"%s\" of type %s does not exist in type %s.",
245 attname,
246 format_type_be(outdesc->tdtypeid),
247 format_type_be(indesc->tdtypeid))));
248 }
249 return attrMap;
250}
251
252/*
253 * build_attrmap_by_name_if_req
254 *
255 * Returns mapping created by build_attrmap_by_name, or NULL if no
256 * conversion is required. This is a convenience routine for
257 * convert_tuples_by_name() in tupconvert.c and other functions, but it
258 * can be used standalone.
259 */
260AttrMap *
261 build_attrmap_by_name_if_req(TupleDesc indesc,
262 TupleDesc outdesc,
263 bool missing_ok)
264{
265 AttrMap *attrMap;
266
267 /* Verify compatibility and prepare attribute-number map */
268 attrMap = build_attrmap_by_name(indesc, outdesc, missing_ok);
269
270 /* Check if the map has a one-to-one match */
271 if (check_attrmap_match(indesc, outdesc, attrMap))
272 {
273 /* Runtime conversion is not needed */
274 free_attrmap(attrMap);
275 return NULL;
276 }
277
278 return attrMap;
279}
280
281/*
282 * check_attrmap_match
283 *
284 * Check to see if the map is a one-to-one match, in which case we need
285 * not to do a tuple conversion, and the attribute map is not necessary.
286 */
287static bool
288 check_attrmap_match(TupleDesc indesc,
289 TupleDesc outdesc,
290 AttrMap *attrMap)
291{
292 int i;
293
294 /* no match if attribute numbers are not the same */
295 if (indesc->natts != outdesc->natts)
296 return false;
297
298 for (i = 0; i < attrMap->maplen; i++)
299 {
300 CompactAttribute *inatt = TupleDescCompactAttr(indesc, i);
301 CompactAttribute *outatt;
302
303 /*
304 * If the input column has a missing attribute, we need a conversion.
305 */
306 if (inatt->atthasmissing)
307 return false;
308
309 if (attrMap->attnums[i] == (i + 1))
310 continue;
311
312 outatt = TupleDescCompactAttr(outdesc, i);
313
314 /*
315 * If it's a dropped column and the corresponding input column is also
316 * dropped, we don't need a conversion. However, attlen and
317 * attalignby must agree.
318 */
319 if (attrMap->attnums[i] == 0 &&
320 inatt->attisdropped &&
321 inatt->attlen == outatt->attlen &&
322 inatt->attalignby == outatt->attalignby)
323 continue;
324
325 return false;
326 }
327
328 return true;
329}
void free_attrmap(AttrMap *map)
Definition: attmap.c:56
AttrMap * make_attrmap(int maplen)
Definition: attmap.c:40
AttrMap * build_attrmap_by_name(TupleDesc indesc, TupleDesc outdesc, bool missing_ok)
Definition: attmap.c:175
AttrMap * build_attrmap_by_name_if_req(TupleDesc indesc, TupleDesc outdesc, bool missing_ok)
Definition: attmap.c:261
static bool check_attrmap_match(TupleDesc indesc, TupleDesc outdesc, AttrMap *attrMap)
Definition: attmap.c:288
AttrMap * build_attrmap_by_position(TupleDesc indesc, TupleDesc outdesc, const char *msg)
Definition: attmap.c:75
int16 AttrNumber
Definition: attnum.h:21
#define NameStr(name)
Definition: c.h:751
int32_t int32
Definition: c.h:534
int errmsg_internal(const char *fmt,...)
Definition: elog.c:1161
int errdetail(const char *fmt,...)
Definition: elog.c:1207
int errcode(int sqlerrcode)
Definition: elog.c:854
int errmsg(const char *fmt,...)
Definition: elog.c:1071
_
#define _(x)
Definition: elog.c:91
#define ERROR
Definition: elog.h:39
#define ereport(elevel,...)
Definition: elog.h:150
char * format_type_with_typemod(Oid type_oid, int32 typemod)
Definition: format_type.c:362
char * format_type_be(Oid type_oid)
Definition: format_type.c:343
j
int j
Definition: isn.c:78
i
int i
Definition: isn.c:77
void pfree(void *pointer)
Definition: mcxt.c:1594
void * palloc0(Size size)
Definition: mcxt.c:1395
NameData attname
Definition: pg_attribute.h:41
FormData_pg_attribute * Form_pg_attribute
Definition: pg_attribute.h:202
unsigned int Oid
Definition: postgres_ext.h:32
Definition: attmap.h:35
int maplen
Definition: attmap.h:37
AttrNumber * attnums
Definition: attmap.h:36
uint8 attalignby
Definition: tupdesc.h:80
bool attisdropped
Definition: tupdesc.h:77
int16 attlen
Definition: tupdesc.h:71
bool atthasmissing
Definition: tupdesc.h:76
int natts
Definition: tupdesc.h:137
Oid tdtypeid
Definition: tupdesc.h:138
static FormData_pg_attribute * TupleDescAttr(TupleDesc tupdesc, int i)
Definition: tupdesc.h:160
static CompactAttribute * TupleDescCompactAttr(TupleDesc tupdesc, int i)
Definition: tupdesc.h:175

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