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postgres.h
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1 /*-------------------------------------------------------------------------
2  *
3  * postgres.h
4  * Primary include file for PostgreSQL server .c files
5  *
6  * This should be the first file included by PostgreSQL backend modules.
7  * Client-side code should include postgres_fe.h instead.
8  *
9  *
10  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
11  * Portions Copyright (c) 1995, Regents of the University of California
12  *
13  * src/include/postgres.h
14  *
15  *-------------------------------------------------------------------------
16  */
17 /*
18  *----------------------------------------------------------------
19  * TABLE OF CONTENTS
20  *
21  * When adding stuff to this file, please try to put stuff
22  * into the relevant section, or add new sections as appropriate.
23  *
24  * section description
25  * ------- ------------------------------------------------
26  * 1) variable-length datatypes (TOAST support)
27  * 2) Datum type + support macros
28  *
29  * NOTES
30  *
31  * In general, this file should contain declarations that are widely needed
32  * in the backend environment, but are of no interest outside the backend.
33  *
34  * Simple type definitions live in c.h, where they are shared with
35  * postgres_fe.h. We do that since those type definitions are needed by
36  * frontend modules that want to deal with binary data transmission to or
37  * from the backend. Type definitions in this file should be for
38  * representations that never escape the backend, such as Datum or
39  * TOASTed varlena objects.
40  *
41  *----------------------------------------------------------------
42  */
43 #ifndef POSTGRES_H
44 #define POSTGRES_H
45 
46 #include "c.h"
47 #include "utils/elog.h"
48 #include "utils/palloc.h"
49 
50 /* ----------------------------------------------------------------
51  * Section 1: variable-length datatypes (TOAST support)
52  * ----------------------------------------------------------------
53  */
54 
55 /*
56  * struct varatt_external is a traditional "TOAST pointer", that is, the
57  * information needed to fetch a Datum stored out-of-line in a TOAST table.
58  * The data is compressed if and only if the external size stored in
59  * va_extinfo is less than va_rawsize - VARHDRSZ.
60  *
61  * This struct must not contain any padding, because we sometimes compare
62  * these pointers using memcmp.
63  *
64  * Note that this information is stored unaligned within actual tuples, so
65  * you need to memcpy from the tuple into a local struct variable before
66  * you can look at these fields! (The reason we use memcmp is to avoid
67  * having to do that just to detect equality of two TOAST pointers...)
68  */
69 typedef struct varatt_external
70 {
71  int32 va_rawsize; /* Original data size (includes header) */
72  uint32 va_extinfo; /* External saved size (without header) and
73  * compression method */
74  Oid va_valueid; /* Unique ID of value within TOAST table */
75  Oid va_toastrelid; /* RelID of TOAST table containing it */
77 
78 /*
79  * These macros define the "saved size" portion of va_extinfo. Its remaining
80  * two high-order bits identify the compression method.
81  */
82 #define VARLENA_EXTSIZE_BITS 30
83 #define VARLENA_EXTSIZE_MASK ((1U << VARLENA_EXTSIZE_BITS) - 1)
84 
85 /*
86  * struct varatt_indirect is a "TOAST pointer" representing an out-of-line
87  * Datum that's stored in memory, not in an external toast relation.
88  * The creator of such a Datum is entirely responsible that the referenced
89  * storage survives for as long as referencing pointer Datums can exist.
90  *
91  * Note that just as for struct varatt_external, this struct is stored
92  * unaligned within any containing tuple.
93  */
94 typedef struct varatt_indirect
95 {
96  struct varlena *pointer; /* Pointer to in-memory varlena */
98 
99 /*
100  * struct varatt_expanded is a "TOAST pointer" representing an out-of-line
101  * Datum that is stored in memory, in some type-specific, not necessarily
102  * physically contiguous format that is convenient for computation not
103  * storage. APIs for this, in particular the definition of struct
104  * ExpandedObjectHeader, are in src/include/utils/expandeddatum.h.
105  *
106  * Note that just as for struct varatt_external, this struct is stored
107  * unaligned within any containing tuple.
108  */
110 
111 typedef struct varatt_expanded
112 {
115 
116 /*
117  * Type tag for the various sorts of "TOAST pointer" datums. The peculiar
118  * value for VARTAG_ONDISK comes from a requirement for on-disk compatibility
119  * with a previous notion that the tag field was the pointer datum's length.
120  */
121 typedef enum vartag_external
122 {
128 
129 /* this test relies on the specific tag values above */
130 #define VARTAG_IS_EXPANDED(tag) \
131  (((tag) & ~1) == VARTAG_EXPANDED_RO)
132 
133 #define VARTAG_SIZE(tag) \
134  ((tag) == VARTAG_INDIRECT ? sizeof(varatt_indirect) : \
135  VARTAG_IS_EXPANDED(tag) ? sizeof(varatt_expanded) : \
136  (tag) == VARTAG_ONDISK ? sizeof(varatt_external) : \
137  TrapMacro(true, "unrecognized TOAST vartag"))
138 
139 /*
140  * These structs describe the header of a varlena object that may have been
141  * TOASTed. Generally, don't reference these structs directly, but use the
142  * macros below.
143  *
144  * We use separate structs for the aligned and unaligned cases because the
145  * compiler might otherwise think it could generate code that assumes
146  * alignment while touching fields of a 1-byte-header varlena.
147  */
148 typedef union
149 {
150  struct /* Normal varlena (4-byte length) */
151  {
153  char va_data[FLEXIBLE_ARRAY_MEMBER];
154  } va_4byte;
155  struct /* Compressed-in-line format */
156  {
157  uint32 va_header;
158  uint32 va_tcinfo; /* Original data size (excludes header) and
159  * compression method; see va_extinfo */
160  char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Compressed data */
161  } va_compressed;
162 } varattrib_4b;
163 
164 typedef struct
165 {
167  char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Data begins here */
168 } varattrib_1b;
169 
170 /* TOAST pointers are a subset of varattrib_1b with an identifying tag byte */
171 typedef struct
172 {
173  uint8 va_header; /* Always 0x80 or 0x01 */
174  uint8 va_tag; /* Type of datum */
175  char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Type-specific data */
177 
178 /*
179  * Bit layouts for varlena headers on big-endian machines:
180  *
181  * 00xxxxxx 4-byte length word, aligned, uncompressed data (up to 1G)
182  * 01xxxxxx 4-byte length word, aligned, *compressed* data (up to 1G)
183  * 10000000 1-byte length word, unaligned, TOAST pointer
184  * 1xxxxxxx 1-byte length word, unaligned, uncompressed data (up to 126b)
185  *
186  * Bit layouts for varlena headers on little-endian machines:
187  *
188  * xxxxxx00 4-byte length word, aligned, uncompressed data (up to 1G)
189  * xxxxxx10 4-byte length word, aligned, *compressed* data (up to 1G)
190  * 00000001 1-byte length word, unaligned, TOAST pointer
191  * xxxxxxx1 1-byte length word, unaligned, uncompressed data (up to 126b)
192  *
193  * The "xxx" bits are the length field (which includes itself in all cases).
194  * In the big-endian case we mask to extract the length, in the little-endian
195  * case we shift. Note that in both cases the flag bits are in the physically
196  * first byte. Also, it is not possible for a 1-byte length word to be zero;
197  * this lets us disambiguate alignment padding bytes from the start of an
198  * unaligned datum. (We now *require* pad bytes to be filled with zero!)
199  *
200  * In TOAST pointers the va_tag field (see varattrib_1b_e) is used to discern
201  * the specific type and length of the pointer datum.
202  */
203 
204 /*
205  * Endian-dependent macros. These are considered internal --- use the
206  * external macros below instead of using these directly.
207  *
208  * Note: IS_1B is true for external toast records but VARSIZE_1B will return 0
209  * for such records. Hence you should usually check for IS_EXTERNAL before
210  * checking for IS_1B.
211  */
212 
213 #ifdef WORDS_BIGENDIAN
214 
215 #define VARATT_IS_4B(PTR) \
216  ((((varattrib_1b *) (PTR))->va_header & 0x80) == 0x00)
217 #define VARATT_IS_4B_U(PTR) \
218  ((((varattrib_1b *) (PTR))->va_header & 0xC0) == 0x00)
219 #define VARATT_IS_4B_C(PTR) \
220  ((((varattrib_1b *) (PTR))->va_header & 0xC0) == 0x40)
221 #define VARATT_IS_1B(PTR) \
222  ((((varattrib_1b *) (PTR))->va_header & 0x80) == 0x80)
223 #define VARATT_IS_1B_E(PTR) \
224  ((((varattrib_1b *) (PTR))->va_header) == 0x80)
225 #define VARATT_NOT_PAD_BYTE(PTR) \
226  (*((uint8 *) (PTR)) != 0)
227 
228 /* VARSIZE_4B() should only be used on known-aligned data */
229 #define VARSIZE_4B(PTR) \
230  (((varattrib_4b *) (PTR))->va_4byte.va_header & 0x3FFFFFFF)
231 #define VARSIZE_1B(PTR) \
232  (((varattrib_1b *) (PTR))->va_header & 0x7F)
233 #define VARTAG_1B_E(PTR) \
234  (((varattrib_1b_e *) (PTR))->va_tag)
235 
236 #define SET_VARSIZE_4B(PTR,len) \
237  (((varattrib_4b *) (PTR))->va_4byte.va_header = (len) & 0x3FFFFFFF)
238 #define SET_VARSIZE_4B_C(PTR,len) \
239  (((varattrib_4b *) (PTR))->va_4byte.va_header = ((len) & 0x3FFFFFFF) | 0x40000000)
240 #define SET_VARSIZE_1B(PTR,len) \
241  (((varattrib_1b *) (PTR))->va_header = (len) | 0x80)
242 #define SET_VARTAG_1B_E(PTR,tag) \
243  (((varattrib_1b_e *) (PTR))->va_header = 0x80, \
244  ((varattrib_1b_e *) (PTR))->va_tag = (tag))
245 
246 #else /* !WORDS_BIGENDIAN */
247 
248 #define VARATT_IS_4B(PTR) \
249  ((((varattrib_1b *) (PTR))->va_header & 0x01) == 0x00)
250 #define VARATT_IS_4B_U(PTR) \
251  ((((varattrib_1b *) (PTR))->va_header & 0x03) == 0x00)
252 #define VARATT_IS_4B_C(PTR) \
253  ((((varattrib_1b *) (PTR))->va_header & 0x03) == 0x02)
254 #define VARATT_IS_1B(PTR) \
255  ((((varattrib_1b *) (PTR))->va_header & 0x01) == 0x01)
256 #define VARATT_IS_1B_E(PTR) \
257  ((((varattrib_1b *) (PTR))->va_header) == 0x01)
258 #define VARATT_NOT_PAD_BYTE(PTR) \
259  (*((uint8 *) (PTR)) != 0)
260 
261 /* VARSIZE_4B() should only be used on known-aligned data */
262 #define VARSIZE_4B(PTR) \
263  ((((varattrib_4b *) (PTR))->va_4byte.va_header >> 2) & 0x3FFFFFFF)
264 #define VARSIZE_1B(PTR) \
265  ((((varattrib_1b *) (PTR))->va_header >> 1) & 0x7F)
266 #define VARTAG_1B_E(PTR) \
267  (((varattrib_1b_e *) (PTR))->va_tag)
268 
269 #define SET_VARSIZE_4B(PTR,len) \
270  (((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2))
271 #define SET_VARSIZE_4B_C(PTR,len) \
272  (((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2) | 0x02)
273 #define SET_VARSIZE_1B(PTR,len) \
274  (((varattrib_1b *) (PTR))->va_header = (((uint8) (len)) << 1) | 0x01)
275 #define SET_VARTAG_1B_E(PTR,tag) \
276  (((varattrib_1b_e *) (PTR))->va_header = 0x01, \
277  ((varattrib_1b_e *) (PTR))->va_tag = (tag))
278 
279 #endif /* WORDS_BIGENDIAN */
280 
281 #define VARDATA_4B(PTR) (((varattrib_4b *) (PTR))->va_4byte.va_data)
282 #define VARDATA_4B_C(PTR) (((varattrib_4b *) (PTR))->va_compressed.va_data)
283 #define VARDATA_1B(PTR) (((varattrib_1b *) (PTR))->va_data)
284 #define VARDATA_1B_E(PTR) (((varattrib_1b_e *) (PTR))->va_data)
285 
286 /*
287  * Externally visible TOAST macros begin here.
288  */
289 
290 #define VARHDRSZ_EXTERNAL offsetof(varattrib_1b_e, va_data)
291 #define VARHDRSZ_COMPRESSED offsetof(varattrib_4b, va_compressed.va_data)
292 #define VARHDRSZ_SHORT offsetof(varattrib_1b, va_data)
293 
294 #define VARATT_SHORT_MAX 0x7F
295 #define VARATT_CAN_MAKE_SHORT(PTR) \
296  (VARATT_IS_4B_U(PTR) && \
297  (VARSIZE(PTR) - VARHDRSZ + VARHDRSZ_SHORT) <= VARATT_SHORT_MAX)
298 #define VARATT_CONVERTED_SHORT_SIZE(PTR) \
299  (VARSIZE(PTR) - VARHDRSZ + VARHDRSZ_SHORT)
300 
301 /*
302  * In consumers oblivious to data alignment, call PG_DETOAST_DATUM_PACKED(),
303  * VARDATA_ANY(), VARSIZE_ANY() and VARSIZE_ANY_EXHDR(). Elsewhere, call
304  * PG_DETOAST_DATUM(), VARDATA() and VARSIZE(). Directly fetching an int16,
305  * int32 or wider field in the struct representing the datum layout requires
306  * aligned data. memcpy() is alignment-oblivious, as are most operations on
307  * datatypes, such as text, whose layout struct contains only char fields.
308  *
309  * Code assembling a new datum should call VARDATA() and SET_VARSIZE().
310  * (Datums begin life untoasted.)
311  *
312  * Other macros here should usually be used only by tuple assembly/disassembly
313  * code and code that specifically wants to work with still-toasted Datums.
314  */
315 #define VARDATA(PTR) VARDATA_4B(PTR)
316 #define VARSIZE(PTR) VARSIZE_4B(PTR)
317 
318 #define VARSIZE_SHORT(PTR) VARSIZE_1B(PTR)
319 #define VARDATA_SHORT(PTR) VARDATA_1B(PTR)
320 
321 #define VARTAG_EXTERNAL(PTR) VARTAG_1B_E(PTR)
322 #define VARSIZE_EXTERNAL(PTR) (VARHDRSZ_EXTERNAL + VARTAG_SIZE(VARTAG_EXTERNAL(PTR)))
323 #define VARDATA_EXTERNAL(PTR) VARDATA_1B_E(PTR)
324 
325 #define VARATT_IS_COMPRESSED(PTR) VARATT_IS_4B_C(PTR)
326 #define VARATT_IS_EXTERNAL(PTR) VARATT_IS_1B_E(PTR)
327 #define VARATT_IS_EXTERNAL_ONDISK(PTR) \
328  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_ONDISK)
329 #define VARATT_IS_EXTERNAL_INDIRECT(PTR) \
330  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_INDIRECT)
331 #define VARATT_IS_EXTERNAL_EXPANDED_RO(PTR) \
332  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_EXPANDED_RO)
333 #define VARATT_IS_EXTERNAL_EXPANDED_RW(PTR) \
334  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_EXPANDED_RW)
335 #define VARATT_IS_EXTERNAL_EXPANDED(PTR) \
336  (VARATT_IS_EXTERNAL(PTR) && VARTAG_IS_EXPANDED(VARTAG_EXTERNAL(PTR)))
337 #define VARATT_IS_EXTERNAL_NON_EXPANDED(PTR) \
338  (VARATT_IS_EXTERNAL(PTR) && !VARTAG_IS_EXPANDED(VARTAG_EXTERNAL(PTR)))
339 #define VARATT_IS_SHORT(PTR) VARATT_IS_1B(PTR)
340 #define VARATT_IS_EXTENDED(PTR) (!VARATT_IS_4B_U(PTR))
341 
342 #define SET_VARSIZE(PTR, len) SET_VARSIZE_4B(PTR, len)
343 #define SET_VARSIZE_SHORT(PTR, len) SET_VARSIZE_1B(PTR, len)
344 #define SET_VARSIZE_COMPRESSED(PTR, len) SET_VARSIZE_4B_C(PTR, len)
345 
346 #define SET_VARTAG_EXTERNAL(PTR, tag) SET_VARTAG_1B_E(PTR, tag)
347 
348 #define VARSIZE_ANY(PTR) \
349  (VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR) : \
350  (VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR) : \
351  VARSIZE_4B(PTR)))
352 
353 /* Size of a varlena data, excluding header */
354 #define VARSIZE_ANY_EXHDR(PTR) \
355  (VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR)-VARHDRSZ_EXTERNAL : \
356  (VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR)-VARHDRSZ_SHORT : \
357  VARSIZE_4B(PTR)-VARHDRSZ))
358 
359 /* caution: this will not work on an external or compressed-in-line Datum */
360 /* caution: this will return a possibly unaligned pointer */
361 #define VARDATA_ANY(PTR) \
362  (VARATT_IS_1B(PTR) ? VARDATA_1B(PTR) : VARDATA_4B(PTR))
363 
364 /* Decompressed size and compression method of an external compressed Datum */
365 #define VARDATA_COMPRESSED_GET_EXTSIZE(PTR) \
366  (((varattrib_4b *) (PTR))->va_compressed.va_tcinfo & VARLENA_EXTSIZE_MASK)
367 #define VARDATA_COMPRESSED_GET_COMPRESS_METHOD(PTR) \
368  (((varattrib_4b *) (PTR))->va_compressed.va_tcinfo >> VARLENA_EXTSIZE_BITS)
369 
370 /* Same, when working directly with a struct varatt_external */
371 #define VARATT_EXTERNAL_GET_EXTSIZE(toast_pointer) \
372  ((toast_pointer).va_extinfo & VARLENA_EXTSIZE_MASK)
373 #define VARATT_EXTERNAL_GET_COMPRESS_METHOD(toast_pointer) \
374  ((toast_pointer).va_extinfo >> VARLENA_EXTSIZE_BITS)
375 
376 #define VARATT_EXTERNAL_SET_SIZE_AND_COMPRESS_METHOD(toast_pointer, len, cm) \
377  do { \
378  Assert((cm) == TOAST_PGLZ_COMPRESSION_ID || \
379  (cm) == TOAST_LZ4_COMPRESSION_ID); \
380  ((toast_pointer).va_extinfo = \
381  (len) | ((uint32) (cm) << VARLENA_EXTSIZE_BITS)); \
382  } while (0)
383 
384 /*
385  * Testing whether an externally-stored value is compressed now requires
386  * comparing size stored in va_extinfo (the actual length of the external data)
387  * to rawsize (the original uncompressed datum's size). The latter includes
388  * VARHDRSZ overhead, the former doesn't. We never use compression unless it
389  * actually saves space, so we expect either equality or less-than.
390  */
391 #define VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) \
392  (VARATT_EXTERNAL_GET_EXTSIZE(toast_pointer) < \
393  (toast_pointer).va_rawsize - VARHDRSZ)
394 
395 
396 /* ----------------------------------------------------------------
397  * Section 2: Datum type + support macros
398  * ----------------------------------------------------------------
399  */
400 
401 /*
402  * A Datum contains either a value of a pass-by-value type or a pointer to a
403  * value of a pass-by-reference type. Therefore, we require:
404  *
405  * sizeof(Datum) == sizeof(void *) == 4 or 8
406  *
407  * The macros below and the analogous macros for other types should be used to
408  * convert between a Datum and the appropriate C type.
409  */
410 
411 typedef uintptr_t Datum;
412 
413 /*
414  * A NullableDatum is used in places where both a Datum and its nullness needs
415  * to be stored. This can be more efficient than storing datums and nullness
416  * in separate arrays, due to better spatial locality, even if more space may
417  * be wasted due to padding.
418  */
419 typedef struct NullableDatum
420 {
421 #define FIELDNO_NULLABLE_DATUM_DATUM 0
423 #define FIELDNO_NULLABLE_DATUM_ISNULL 1
424  bool isnull;
425  /* due to alignment padding this could be used for flags for free */
426 } NullableDatum;
427 
428 #define SIZEOF_DATUM SIZEOF_VOID_P
429 
430 /*
431  * DatumGetBool
432  * Returns boolean value of a datum.
433  *
434  * Note: any nonzero value will be considered true.
435  */
436 
437 #define DatumGetBool(X) ((bool) ((X) != 0))
438 
439 /*
440  * BoolGetDatum
441  * Returns datum representation for a boolean.
442  *
443  * Note: any nonzero value will be considered true.
444  */
445 
446 #define BoolGetDatum(X) ((Datum) ((X) ? 1 : 0))
447 
448 /*
449  * DatumGetChar
450  * Returns character value of a datum.
451  */
452 
453 #define DatumGetChar(X) ((char) (X))
454 
455 /*
456  * CharGetDatum
457  * Returns datum representation for a character.
458  */
459 
460 #define CharGetDatum(X) ((Datum) (X))
461 
462 /*
463  * Int8GetDatum
464  * Returns datum representation for an 8-bit integer.
465  */
466 
467 #define Int8GetDatum(X) ((Datum) (X))
468 
469 /*
470  * DatumGetUInt8
471  * Returns 8-bit unsigned integer value of a datum.
472  */
473 
474 #define DatumGetUInt8(X) ((uint8) (X))
475 
476 /*
477  * UInt8GetDatum
478  * Returns datum representation for an 8-bit unsigned integer.
479  */
480 
481 #define UInt8GetDatum(X) ((Datum) (X))
482 
483 /*
484  * DatumGetInt16
485  * Returns 16-bit integer value of a datum.
486  */
487 
488 #define DatumGetInt16(X) ((int16) (X))
489 
490 /*
491  * Int16GetDatum
492  * Returns datum representation for a 16-bit integer.
493  */
494 
495 #define Int16GetDatum(X) ((Datum) (X))
496 
497 /*
498  * DatumGetUInt16
499  * Returns 16-bit unsigned integer value of a datum.
500  */
501 
502 #define DatumGetUInt16(X) ((uint16) (X))
503 
504 /*
505  * UInt16GetDatum
506  * Returns datum representation for a 16-bit unsigned integer.
507  */
508 
509 #define UInt16GetDatum(X) ((Datum) (X))
510 
511 /*
512  * DatumGetInt32
513  * Returns 32-bit integer value of a datum.
514  */
515 
516 #define DatumGetInt32(X) ((int32) (X))
517 
518 /*
519  * Int32GetDatum
520  * Returns datum representation for a 32-bit integer.
521  */
522 
523 #define Int32GetDatum(X) ((Datum) (X))
524 
525 /*
526  * DatumGetUInt32
527  * Returns 32-bit unsigned integer value of a datum.
528  */
529 
530 #define DatumGetUInt32(X) ((uint32) (X))
531 
532 /*
533  * UInt32GetDatum
534  * Returns datum representation for a 32-bit unsigned integer.
535  */
536 
537 #define UInt32GetDatum(X) ((Datum) (X))
538 
539 /*
540  * DatumGetObjectId
541  * Returns object identifier value of a datum.
542  */
543 
544 #define DatumGetObjectId(X) ((Oid) (X))
545 
546 /*
547  * ObjectIdGetDatum
548  * Returns datum representation for an object identifier.
549  */
550 
551 #define ObjectIdGetDatum(X) ((Datum) (X))
552 
553 /*
554  * DatumGetTransactionId
555  * Returns transaction identifier value of a datum.
556  */
557 
558 #define DatumGetTransactionId(X) ((TransactionId) (X))
559 
560 /*
561  * TransactionIdGetDatum
562  * Returns datum representation for a transaction identifier.
563  */
564 
565 #define TransactionIdGetDatum(X) ((Datum) (X))
566 
567 /*
568  * MultiXactIdGetDatum
569  * Returns datum representation for a multixact identifier.
570  */
571 
572 #define MultiXactIdGetDatum(X) ((Datum) (X))
573 
574 /*
575  * DatumGetCommandId
576  * Returns command identifier value of a datum.
577  */
578 
579 #define DatumGetCommandId(X) ((CommandId) (X))
580 
581 /*
582  * CommandIdGetDatum
583  * Returns datum representation for a command identifier.
584  */
585 
586 #define CommandIdGetDatum(X) ((Datum) (X))
587 
588 /*
589  * DatumGetPointer
590  * Returns pointer value of a datum.
591  */
592 
593 #define DatumGetPointer(X) ((Pointer) (X))
594 
595 /*
596  * PointerGetDatum
597  * Returns datum representation for a pointer.
598  */
599 
600 #define PointerGetDatum(X) ((Datum) (X))
601 
602 /*
603  * DatumGetCString
604  * Returns C string (null-terminated string) value of a datum.
605  *
606  * Note: C string is not a full-fledged Postgres type at present,
607  * but type input functions use this conversion for their inputs.
608  */
609 
610 #define DatumGetCString(X) ((char *) DatumGetPointer(X))
611 
612 /*
613  * CStringGetDatum
614  * Returns datum representation for a C string (null-terminated string).
615  *
616  * Note: C string is not a full-fledged Postgres type at present,
617  * but type output functions use this conversion for their outputs.
618  * Note: CString is pass-by-reference; caller must ensure the pointed-to
619  * value has adequate lifetime.
620  */
621 
622 #define CStringGetDatum(X) PointerGetDatum(X)
623 
624 /*
625  * DatumGetName
626  * Returns name value of a datum.
627  */
628 
629 #define DatumGetName(X) ((Name) DatumGetPointer(X))
630 
631 /*
632  * NameGetDatum
633  * Returns datum representation for a name.
634  *
635  * Note: Name is pass-by-reference; caller must ensure the pointed-to
636  * value has adequate lifetime.
637  */
638 
639 #define NameGetDatum(X) CStringGetDatum(NameStr(*(X)))
640 
641 /*
642  * DatumGetInt64
643  * Returns 64-bit integer value of a datum.
644  *
645  * Note: this macro hides whether int64 is pass by value or by reference.
646  */
647 
648 #ifdef USE_FLOAT8_BYVAL
649 #define DatumGetInt64(X) ((int64) (X))
650 #else
651 #define DatumGetInt64(X) (* ((int64 *) DatumGetPointer(X)))
652 #endif
653 
654 /*
655  * Int64GetDatum
656  * Returns datum representation for a 64-bit integer.
657  *
658  * Note: if int64 is pass by reference, this function returns a reference
659  * to palloc'd space.
660  */
661 
662 #ifdef USE_FLOAT8_BYVAL
663 #define Int64GetDatum(X) ((Datum) (X))
664 #else
665 extern Datum Int64GetDatum(int64 X);
666 #endif
667 
668 /*
669  * DatumGetUInt64
670  * Returns 64-bit unsigned integer value of a datum.
671  *
672  * Note: this macro hides whether int64 is pass by value or by reference.
673  */
674 
675 #ifdef USE_FLOAT8_BYVAL
676 #define DatumGetUInt64(X) ((uint64) (X))
677 #else
678 #define DatumGetUInt64(X) (* ((uint64 *) DatumGetPointer(X)))
679 #endif
680 
681 /*
682  * UInt64GetDatum
683  * Returns datum representation for a 64-bit unsigned integer.
684  *
685  * Note: if int64 is pass by reference, this function returns a reference
686  * to palloc'd space.
687  */
688 
689 #ifdef USE_FLOAT8_BYVAL
690 #define UInt64GetDatum(X) ((Datum) (X))
691 #else
692 #define UInt64GetDatum(X) Int64GetDatum((int64) (X))
693 #endif
694 
695 /*
696  * Float <-> Datum conversions
697  *
698  * These have to be implemented as inline functions rather than macros, when
699  * passing by value, because many machines pass int and float function
700  * parameters/results differently; so we need to play weird games with unions.
701  */
702 
703 /*
704  * DatumGetFloat4
705  * Returns 4-byte floating point value of a datum.
706  */
707 static inline float4
709 {
710  union
711  {
712  int32 value;
713  float4 retval;
714  } myunion;
715 
716  myunion.value = DatumGetInt32(X);
717  return myunion.retval;
718 }
719 
720 /*
721  * Float4GetDatum
722  * Returns datum representation for a 4-byte floating point number.
723  */
724 static inline Datum
726 {
727  union
728  {
729  float4 value;
730  int32 retval;
731  } myunion;
732 
733  myunion.value = X;
734  return Int32GetDatum(myunion.retval);
735 }
736 
737 /*
738  * DatumGetFloat8
739  * Returns 8-byte floating point value of a datum.
740  *
741  * Note: this macro hides whether float8 is pass by value or by reference.
742  */
743 
744 #ifdef USE_FLOAT8_BYVAL
745 static inline float8
747 {
748  union
749  {
750  int64 value;
751  float8 retval;
752  } myunion;
753 
754  myunion.value = DatumGetInt64(X);
755  return myunion.retval;
756 }
757 #else
758 #define DatumGetFloat8(X) (* ((float8 *) DatumGetPointer(X)))
759 #endif
760 
761 /*
762  * Float8GetDatum
763  * Returns datum representation for an 8-byte floating point number.
764  *
765  * Note: if float8 is pass by reference, this function returns a reference
766  * to palloc'd space.
767  */
768 
769 #ifdef USE_FLOAT8_BYVAL
770 static inline Datum
772 {
773  union
774  {
775  float8 value;
776  int64 retval;
777  } myunion;
778 
779  myunion.value = X;
780  return Int64GetDatum(myunion.retval);
781 }
782 #else
783 extern Datum Float8GetDatum(float8 X);
784 #endif
785 
786 
787 /*
788  * Int64GetDatumFast
789  * Float8GetDatumFast
790  *
791  * These macros are intended to allow writing code that does not depend on
792  * whether int64 and float8 are pass-by-reference types, while not
793  * sacrificing performance when they are. The argument must be a variable
794  * that will exist and have the same value for as long as the Datum is needed.
795  * In the pass-by-ref case, the address of the variable is taken to use as
796  * the Datum. In the pass-by-val case, these will be the same as the non-Fast
797  * macros.
798  */
799 
800 #ifdef USE_FLOAT8_BYVAL
801 #define Int64GetDatumFast(X) Int64GetDatum(X)
802 #define Float8GetDatumFast(X) Float8GetDatum(X)
803 #else
804 #define Int64GetDatumFast(X) PointerGetDatum(&(X))
805 #define Float8GetDatumFast(X) PointerGetDatum(&(X))
806 #endif
807 
808 #endif /* POSTGRES_H */
static Datum Float4GetDatum(float4 X)
Definition: postgres.h:725
vartag_external
Definition: postgres.h:121
ExpandedObjectHeader * eohptr
Definition: postgres.h:113
struct varatt_expanded varatt_expanded
static struct @142 value
#define DatumGetInt32(X)
Definition: postgres.h:516
uint8 va_tag
Definition: postgres.h:174
uint32 va_tcinfo
Definition: postgres.h:158
unsigned char uint8
Definition: c.h:439
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:350
Oid va_toastrelid
Definition: postgres.h:75
int32 va_rawsize
Definition: postgres.h:71
unsigned int Oid
Definition: postgres_ext.h:31
struct NullableDatum NullableDatum
signed int int32
Definition: c.h:429
struct varatt_external varatt_external
static float4 DatumGetFloat4(Datum X)
Definition: postgres.h:708
double float8
Definition: c.h:565
Datum Float8GetDatum(float8 X)
Definition: fmgr.c:1706
#define DatumGetInt64(X)
Definition: postgres.h:651
unsigned int uint32
Definition: c.h:441
Datum value
Definition: postgres.h:422
uint8 va_header
Definition: postgres.h:166
float float4
Definition: c.h:564
uint8 va_header
Definition: postgres.h:173
#define DatumGetFloat8(X)
Definition: postgres.h:758
uintptr_t Datum
Definition: postgres.h:411
uint32 va_extinfo
Definition: postgres.h:72
uint32 va_header
Definition: postgres.h:152
struct varlena * pointer
Definition: postgres.h:96
#define Int32GetDatum(X)
Definition: postgres.h:523
Datum Int64GetDatum(int64 X)
Definition: fmgr.c:1697
Definition: c.h:621
struct varatt_indirect varatt_indirect