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tupconvert.c
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1 /*-------------------------------------------------------------------------
2  *
3  * tupconvert.c
4  * Tuple conversion support.
5  *
6  * These functions provide conversion between rowtypes that are logically
7  * equivalent but might have columns in a different order or different sets
8  * of dropped columns. There is some overlap of functionality with the
9  * executor's "junkfilter" routines, but these functions work on bare
10  * HeapTuples rather than TupleTableSlots.
11  *
12  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
13  * Portions Copyright (c) 1994, Regents of the University of California
14  *
15  *
16  * IDENTIFICATION
17  * src/backend/access/common/tupconvert.c
18  *
19  *-------------------------------------------------------------------------
20  */
21 #include "postgres.h"
22 
23 #include "access/htup_details.h"
24 #include "access/tupconvert.h"
25 #include "utils/builtins.h"
26 
27 
28 /*
29  * The conversion setup routines have the following common API:
30  *
31  * The setup routine checks whether the given source and destination tuple
32  * descriptors are logically compatible. If not, it throws an error.
33  * If so, it returns NULL if they are physically compatible (ie, no conversion
34  * is needed), else a TupleConversionMap that can be used by do_convert_tuple
35  * to perform the conversion.
36  *
37  * The TupleConversionMap, if needed, is palloc'd in the caller's memory
38  * context. Also, the given tuple descriptors are referenced by the map,
39  * so they must survive as long as the map is needed.
40  *
41  * The caller must supply a suitable primary error message to be used if
42  * a compatibility error is thrown. Recommended coding practice is to use
43  * gettext_noop() on this string, so that it is translatable but won't
44  * actually be translated unless the error gets thrown.
45  *
46  *
47  * Implementation notes:
48  *
49  * The key component of a TupleConversionMap is an attrMap[] array with
50  * one entry per output column. This entry contains the 1-based index of
51  * the corresponding input column, or zero to force a NULL value (for
52  * a dropped output column). The TupleConversionMap also contains workspace
53  * arrays.
54  */
55 
56 
57 /*
58  * Set up for tuple conversion, matching input and output columns by
59  * position. (Dropped columns are ignored in both input and output.)
60  *
61  * Note: the errdetail messages speak of indesc as the "returned" rowtype,
62  * outdesc as the "expected" rowtype. This is okay for current uses but
63  * might need generalization in future.
64  */
67  TupleDesc outdesc,
68  const char *msg)
69 {
70  TupleConversionMap *map;
71  AttrNumber *attrMap;
72  int nincols;
73  int noutcols;
74  int n;
75  int i;
76  int j;
77  bool same;
78 
79  /* Verify compatibility and prepare attribute-number map */
80  n = outdesc->natts;
81  attrMap = (AttrNumber *) palloc0(n * sizeof(AttrNumber));
82  j = 0; /* j is next physical input attribute */
83  nincols = noutcols = 0; /* these count non-dropped attributes */
84  same = true;
85  for (i = 0; i < n; i++)
86  {
87  Form_pg_attribute att = TupleDescAttr(outdesc, i);
88  Oid atttypid;
89  int32 atttypmod;
90 
91  if (att->attisdropped)
92  continue; /* attrMap[i] is already 0 */
93  noutcols++;
94  atttypid = att->atttypid;
95  atttypmod = att->atttypmod;
96  for (; j < indesc->natts; j++)
97  {
98  att = TupleDescAttr(indesc, j);
99  if (att->attisdropped)
100  continue;
101  nincols++;
102  /* Found matching column, check type */
103  if (atttypid != att->atttypid ||
104  (atttypmod != att->atttypmod && atttypmod >= 0))
105  ereport(ERROR,
106  (errcode(ERRCODE_DATATYPE_MISMATCH),
107  errmsg_internal("%s", _(msg)),
108  errdetail("Returned type %s does not match expected type %s in column %d.",
109  format_type_with_typemod(att->atttypid,
110  att->atttypmod),
111  format_type_with_typemod(atttypid,
112  atttypmod),
113  noutcols)));
114  attrMap[i] = (AttrNumber) (j + 1);
115  j++;
116  break;
117  }
118  if (attrMap[i] == 0)
119  same = false; /* we'll complain below */
120  }
121 
122  /* Check for unused input columns */
123  for (; j < indesc->natts; j++)
124  {
125  if (TupleDescAttr(indesc, j)->attisdropped)
126  continue;
127  nincols++;
128  same = false; /* we'll complain below */
129  }
130 
131  /* Report column count mismatch using the non-dropped-column counts */
132  if (!same)
133  ereport(ERROR,
134  (errcode(ERRCODE_DATATYPE_MISMATCH),
135  errmsg_internal("%s", _(msg)),
136  errdetail("Number of returned columns (%d) does not match "
137  "expected column count (%d).",
138  nincols, noutcols)));
139 
140  /*
141  * Check to see if the map is one-to-one, in which case we need not do a
142  * tuple conversion. We must also insist that both tupdescs either
143  * specify or don't specify an OID column, else we need a conversion to
144  * add/remove space for that. (For some callers, presence or absence of
145  * an OID column perhaps would not really matter, but let's be safe.)
146  */
147  if (indesc->natts == outdesc->natts &&
148  indesc->tdhasoid == outdesc->tdhasoid)
149  {
150  for (i = 0; i < n; i++)
151  {
152  Form_pg_attribute inatt;
153  Form_pg_attribute outatt;
154 
155  if (attrMap[i] == (i + 1))
156  continue;
157 
158  /*
159  * If it's a dropped column and the corresponding input column is
160  * also dropped, we needn't convert. However, attlen and attalign
161  * must agree.
162  */
163  inatt = TupleDescAttr(indesc, i);
164  outatt = TupleDescAttr(outdesc, i);
165  if (attrMap[i] == 0 &&
166  inatt->attisdropped &&
167  inatt->attlen == outatt->attlen &&
168  inatt->attalign == outatt->attalign)
169  continue;
170 
171  same = false;
172  break;
173  }
174  }
175  else
176  same = false;
177 
178  if (same)
179  {
180  /* Runtime conversion is not needed */
181  pfree(attrMap);
182  return NULL;
183  }
184 
185  /* Prepare the map structure */
186  map = (TupleConversionMap *) palloc(sizeof(TupleConversionMap));
187  map->indesc = indesc;
188  map->outdesc = outdesc;
189  map->attrMap = attrMap;
190  /* preallocate workspace for Datum arrays */
191  map->outvalues = (Datum *) palloc(n * sizeof(Datum));
192  map->outisnull = (bool *) palloc(n * sizeof(bool));
193  n = indesc->natts + 1; /* +1 for NULL */
194  map->invalues = (Datum *) palloc(n * sizeof(Datum));
195  map->inisnull = (bool *) palloc(n * sizeof(bool));
196  map->invalues[0] = (Datum) 0; /* set up the NULL entry */
197  map->inisnull[0] = true;
198 
199  return map;
200 }
201 
202 /*
203  * Set up for tuple conversion, matching input and output columns by name.
204  * (Dropped columns are ignored in both input and output.) This is intended
205  * for use when the rowtypes are related by inheritance, so we expect an exact
206  * match of both type and typmod. The error messages will be a bit unhelpful
207  * unless both rowtypes are named composite types.
208  */
211  TupleDesc outdesc,
212  const char *msg)
213 {
214  TupleConversionMap *map;
215  AttrNumber *attrMap;
216  int n = outdesc->natts;
217  int i;
218  bool same;
219 
220  /* Verify compatibility and prepare attribute-number map */
221  attrMap = convert_tuples_by_name_map(indesc, outdesc, msg);
222 
223  /*
224  * Check to see if the map is one-to-one, in which case we need not do a
225  * tuple conversion. We must also insist that both tupdescs either
226  * specify or don't specify an OID column, else we need a conversion to
227  * add/remove space for that. (For some callers, presence or absence of
228  * an OID column perhaps would not really matter, but let's be safe.)
229  */
230  if (indesc->natts == outdesc->natts &&
231  indesc->tdhasoid == outdesc->tdhasoid)
232  {
233  same = true;
234  for (i = 0; i < n; i++)
235  {
236  Form_pg_attribute inatt;
237  Form_pg_attribute outatt;
238 
239  if (attrMap[i] == (i + 1))
240  continue;
241 
242  /*
243  * If it's a dropped column and the corresponding input column is
244  * also dropped, we needn't convert. However, attlen and attalign
245  * must agree.
246  */
247  inatt = TupleDescAttr(indesc, i);
248  outatt = TupleDescAttr(outdesc, i);
249  if (attrMap[i] == 0 &&
250  inatt->attisdropped &&
251  inatt->attlen == outatt->attlen &&
252  inatt->attalign == outatt->attalign)
253  continue;
254 
255  same = false;
256  break;
257  }
258  }
259  else
260  same = false;
261 
262  if (same)
263  {
264  /* Runtime conversion is not needed */
265  pfree(attrMap);
266  return NULL;
267  }
268 
269  /* Prepare the map structure */
270  map = (TupleConversionMap *) palloc(sizeof(TupleConversionMap));
271  map->indesc = indesc;
272  map->outdesc = outdesc;
273  map->attrMap = attrMap;
274  /* preallocate workspace for Datum arrays */
275  map->outvalues = (Datum *) palloc(n * sizeof(Datum));
276  map->outisnull = (bool *) palloc(n * sizeof(bool));
277  n = indesc->natts + 1; /* +1 for NULL */
278  map->invalues = (Datum *) palloc(n * sizeof(Datum));
279  map->inisnull = (bool *) palloc(n * sizeof(bool));
280  map->invalues[0] = (Datum) 0; /* set up the NULL entry */
281  map->inisnull[0] = true;
282 
283  return map;
284 }
285 
286 /*
287  * Return a palloc'd bare attribute map for tuple conversion, matching input
288  * and output columns by name. (Dropped columns are ignored in both input and
289  * output.) This is normally a subroutine for convert_tuples_by_name, but can
290  * be used standalone.
291  */
292 AttrNumber *
294  TupleDesc outdesc,
295  const char *msg)
296 {
297  AttrNumber *attrMap;
298  int n;
299  int i;
300 
301  n = outdesc->natts;
302  attrMap = (AttrNumber *) palloc0(n * sizeof(AttrNumber));
303  for (i = 0; i < n; i++)
304  {
305  Form_pg_attribute outatt = TupleDescAttr(outdesc, i);
306  char *attname;
307  Oid atttypid;
308  int32 atttypmod;
309  int j;
310 
311  if (outatt->attisdropped)
312  continue; /* attrMap[i] is already 0 */
313  attname = NameStr(outatt->attname);
314  atttypid = outatt->atttypid;
315  atttypmod = outatt->atttypmod;
316  for (j = 0; j < indesc->natts; j++)
317  {
318  Form_pg_attribute inatt = TupleDescAttr(indesc, j);
319 
320  if (inatt->attisdropped)
321  continue;
322  if (strcmp(attname, NameStr(inatt->attname)) == 0)
323  {
324  /* Found it, check type */
325  if (atttypid != inatt->atttypid || atttypmod != inatt->atttypmod)
326  ereport(ERROR,
327  (errcode(ERRCODE_DATATYPE_MISMATCH),
328  errmsg_internal("%s", _(msg)),
329  errdetail("Attribute \"%s\" of type %s does not match corresponding attribute of type %s.",
330  attname,
331  format_type_be(outdesc->tdtypeid),
332  format_type_be(indesc->tdtypeid))));
333  attrMap[i] = (AttrNumber) (j + 1);
334  break;
335  }
336  }
337  if (attrMap[i] == 0)
338  ereport(ERROR,
339  (errcode(ERRCODE_DATATYPE_MISMATCH),
340  errmsg_internal("%s", _(msg)),
341  errdetail("Attribute \"%s\" of type %s does not exist in type %s.",
342  attname,
343  format_type_be(outdesc->tdtypeid),
344  format_type_be(indesc->tdtypeid))));
345  }
346 
347  return attrMap;
348 }
349 
350 /*
351  * Perform conversion of a tuple according to the map.
352  */
353 HeapTuple
355 {
356  AttrNumber *attrMap = map->attrMap;
357  Datum *invalues = map->invalues;
358  bool *inisnull = map->inisnull;
359  Datum *outvalues = map->outvalues;
360  bool *outisnull = map->outisnull;
361  int outnatts = map->outdesc->natts;
362  int i;
363 
364  /*
365  * Extract all the values of the old tuple, offsetting the arrays so that
366  * invalues[0] is left NULL and invalues[1] is the first source attribute;
367  * this exactly matches the numbering convention in attrMap.
368  */
369  heap_deform_tuple(tuple, map->indesc, invalues + 1, inisnull + 1);
370 
371  /*
372  * Transpose into proper fields of the new tuple.
373  */
374  for (i = 0; i < outnatts; i++)
375  {
376  int j = attrMap[i];
377 
378  outvalues[i] = invalues[j];
379  outisnull[i] = inisnull[j];
380  }
381 
382  /*
383  * Now form the new tuple.
384  */
385  return heap_form_tuple(map->outdesc, outvalues, outisnull);
386 }
387 
388 /*
389  * Free a TupleConversionMap structure.
390  */
391 void
393 {
394  /* indesc and outdesc are not ours to free */
395  pfree(map->attrMap);
396  pfree(map->invalues);
397  pfree(map->inisnull);
398  pfree(map->outvalues);
399  pfree(map->outisnull);
400  pfree(map);
401 }
AttrNumber * attrMap
Definition: tupconvert.h:25
TupleDesc indesc
Definition: tupconvert.h:23
Oid tdtypeid
Definition: tupdesc.h:74
TupleDesc outdesc
Definition: tupconvert.h:24
bool tdhasoid
Definition: tupdesc.h:76
TupleConversionMap * convert_tuples_by_position(TupleDesc indesc, TupleDesc outdesc, const char *msg)
Definition: tupconvert.c:66
#define TupleDescAttr(tupdesc, i)
Definition: tupdesc.h:84
int errcode(int sqlerrcode)
Definition: elog.c:575
char * format_type_be(Oid type_oid)
Definition: format_type.c:94
HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull)
Definition: heaptuple.c:695
unsigned int Oid
Definition: postgres_ext.h:31
int natts
Definition: tupdesc.h:73
signed int int32
Definition: c.h:246
void pfree(void *pointer)
Definition: mcxt.c:949
#define ERROR
Definition: elog.h:43
int errdetail(const char *fmt,...)
Definition: elog.c:873
void free_conversion_map(TupleConversionMap *map)
Definition: tupconvert.c:392
FormData_pg_attribute * Form_pg_attribute
Definition: pg_attribute.h:187
#define ereport(elevel, rest)
Definition: elog.h:122
TupleConversionMap * convert_tuples_by_name(TupleDesc indesc, TupleDesc outdesc, const char *msg)
Definition: tupconvert.c:210
AttrNumber * convert_tuples_by_name_map(TupleDesc indesc, TupleDesc outdesc, const char *msg)
Definition: tupconvert.c:293
char * format_type_with_typemod(Oid type_oid, int32 typemod)
Definition: format_type.c:113
void * palloc0(Size size)
Definition: mcxt.c:877
uintptr_t Datum
Definition: postgres.h:372
int errmsg_internal(const char *fmt,...)
Definition: elog.c:827
HeapTuple do_convert_tuple(HeapTuple tuple, TupleConversionMap *map)
Definition: tupconvert.c:354
void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull)
Definition: heaptuple.c:936
void * palloc(Size size)
Definition: mcxt.c:848
int i
#define NameStr(name)
Definition: c.h:493
int16 AttrNumber
Definition: attnum.h:21
#define _(x)
Definition: elog.c:84