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1 : /*-------------------------------------------------------------------------
2 : *
3 : * tuptable.h
4 : * tuple table support stuff
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * src/include/executor/tuptable.h
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 : #ifndef TUPTABLE_H
15 : #define TUPTABLE_H
16 :
17 : #include "access/htup.h"
18 : #include "access/htup_details.h"
19 : #include "access/sysattr.h"
20 : #include "access/tupdesc.h"
21 : #include "storage/buf.h"
22 :
23 : /*----------
24 : * The executor stores tuples in a "tuple table" which is a List of
25 : * independent TupleTableSlots.
26 : *
27 : * There's various different types of tuple table slots, each being able to
28 : * store different types of tuples. Additional types of slots can be added
29 : * without modifying core code. The type of a slot is determined by the
30 : * TupleTableSlotOps* passed to the slot creation routine. The builtin types
31 : * of slots are
32 : *
33 : * 1. physical tuple in a disk buffer page (TTSOpsBufferHeapTuple)
34 : * 2. physical tuple constructed in palloc'ed memory (TTSOpsHeapTuple)
35 : * 3. "minimal" physical tuple constructed in palloc'ed memory
36 : * (TTSOpsMinimalTuple)
37 : * 4. "virtual" tuple consisting of Datum/isnull arrays (TTSOpsVirtual)
38 : *
39 : *
40 : * The first two cases are similar in that they both deal with "materialized"
41 : * tuples, but resource management is different. For a tuple in a disk page
42 : * we need to hold a pin on the buffer until the TupleTableSlot's reference
43 : * to the tuple is dropped; while for a palloc'd tuple we usually want the
44 : * tuple pfree'd when the TupleTableSlot's reference is dropped.
45 : *
46 : * A "minimal" tuple is handled similarly to a palloc'd regular tuple.
47 : * At present, minimal tuples never are stored in buffers, so there is no
48 : * parallel to case 1. Note that a minimal tuple has no "system columns".
49 : * (Actually, it could have an OID, but we have no need to access the OID.)
50 : *
51 : * A "virtual" tuple is an optimization used to minimize physical data copying
52 : * in a nest of plan nodes. Until materialized pass-by-reference Datums in
53 : * the slot point to storage that is not directly associated with the
54 : * TupleTableSlot; generally they will point to part of a tuple stored in a
55 : * lower plan node's output TupleTableSlot, or to a function result
56 : * constructed in a plan node's per-tuple econtext. It is the responsibility
57 : * of the generating plan node to be sure these resources are not released for
58 : * as long as the virtual tuple needs to be valid or is materialized. Note
59 : * also that a virtual tuple does not have any "system columns".
60 : *
61 : * The Datum/isnull arrays of a TupleTableSlot serve double duty. For virtual
62 : * slots they are the authoritative data. For the other builtin slots,
63 : * the arrays contain data extracted from the tuple. (In this state, any
64 : * pass-by-reference Datums point into the physical tuple.) The extracted
65 : * information is built "lazily", ie, only as needed. This serves to avoid
66 : * repeated extraction of data from the physical tuple.
67 : *
68 : * A TupleTableSlot can also be "empty", indicated by flag TTS_FLAG_EMPTY set
69 : * in tts_flags, holding no valid data. This is the only valid state for a
70 : * freshly-created slot that has not yet had a tuple descriptor assigned to
71 : * it. In this state, TTS_SHOULDFREE should not be set in tts_flags, tts_tuple
72 : * must be NULL and tts_nvalid zero.
73 : *
74 : * The tupleDescriptor is simply referenced, not copied, by the TupleTableSlot
75 : * code. The caller of ExecSetSlotDescriptor() is responsible for providing
76 : * a descriptor that will live as long as the slot does. (Typically, both
77 : * slots and descriptors are in per-query memory and are freed by memory
78 : * context deallocation at query end; so it's not worth providing any extra
79 : * mechanism to do more. However, the slot will increment the tupdesc
80 : * reference count if a reference-counted tupdesc is supplied.)
81 : *
82 : * When TTS_SHOULDFREE is set in tts_flags, the physical tuple is "owned" by
83 : * the slot and should be freed when the slot's reference to the tuple is
84 : * dropped.
85 : *
86 : * tts_values/tts_isnull are allocated either when the slot is created (when
87 : * the descriptor is provided), or when a descriptor is assigned to the slot;
88 : * they are of length equal to the descriptor's natts.
89 : *
90 : * The TTS_FLAG_SLOW flag is saved state for
91 : * slot_deform_heap_tuple, and should not be touched by any other code.
92 : *----------
93 : */
94 :
95 : /* true = slot is empty */
96 : #define TTS_FLAG_EMPTY (1 << 1)
97 : #define TTS_EMPTY(slot) (((slot)->tts_flags & TTS_FLAG_EMPTY) != 0)
98 :
99 : /* should pfree tuple "owned" by the slot? */
100 : #define TTS_FLAG_SHOULDFREE (1 << 2)
101 : #define TTS_SHOULDFREE(slot) (((slot)->tts_flags & TTS_FLAG_SHOULDFREE) != 0)
102 :
103 : /* saved state for slot_deform_heap_tuple */
104 : #define TTS_FLAG_SLOW (1 << 3)
105 : #define TTS_SLOW(slot) (((slot)->tts_flags & TTS_FLAG_SLOW) != 0)
106 :
107 : /* fixed tuple descriptor */
108 : #define TTS_FLAG_FIXED (1 << 4)
109 : #define TTS_FIXED(slot) (((slot)->tts_flags & TTS_FLAG_FIXED) != 0)
110 :
111 : struct TupleTableSlotOps;
112 : typedef struct TupleTableSlotOps TupleTableSlotOps;
113 :
114 : /* base tuple table slot type */
115 : typedef struct TupleTableSlot
116 : {
117 : NodeTag type;
118 : #define FIELDNO_TUPLETABLESLOT_FLAGS 1
119 : uint16 tts_flags; /* Boolean states */
120 : #define FIELDNO_TUPLETABLESLOT_NVALID 2
121 : AttrNumber tts_nvalid; /* # of valid values in tts_values */
122 : const TupleTableSlotOps *const tts_ops; /* implementation of slot */
123 : #define FIELDNO_TUPLETABLESLOT_TUPLEDESCRIPTOR 4
124 : TupleDesc tts_tupleDescriptor; /* slot's tuple descriptor */
125 : #define FIELDNO_TUPLETABLESLOT_VALUES 5
126 : Datum *tts_values; /* current per-attribute values */
127 : #define FIELDNO_TUPLETABLESLOT_ISNULL 6
128 : bool *tts_isnull; /* current per-attribute isnull flags */
129 : MemoryContext tts_mcxt; /* slot itself is in this context */
130 : ItemPointerData tts_tid; /* stored tuple's tid */
131 : Oid tts_tableOid; /* table oid of tuple */
132 : } TupleTableSlot;
133 :
134 : /* routines for a TupleTableSlot implementation */
135 : struct TupleTableSlotOps
136 : {
137 : /* Minimum size of the slot */
138 : size_t base_slot_size;
139 :
140 : /* Initialization. */
141 : void (*init) (TupleTableSlot *slot);
142 :
143 : /* Destruction. */
144 : void (*release) (TupleTableSlot *slot);
145 :
146 : /*
147 : * Clear the contents of the slot. Only the contents are expected to be
148 : * cleared and not the tuple descriptor. Typically an implementation of
149 : * this callback should free the memory allocated for the tuple contained
150 : * in the slot.
151 : */
152 : void (*clear) (TupleTableSlot *slot);
153 :
154 : /*
155 : * Fill up first natts entries of tts_values and tts_isnull arrays with
156 : * values from the tuple contained in the slot. The function may be called
157 : * with natts more than the number of attributes available in the tuple,
158 : * in which case it should set tts_nvalid to the number of returned
159 : * columns.
160 : */
161 : void (*getsomeattrs) (TupleTableSlot *slot, int natts);
162 :
163 : /*
164 : * Returns value of the given system attribute as a datum and sets isnull
165 : * to false, if it's not NULL. Throws an error if the slot type does not
166 : * support system attributes.
167 : */
168 : Datum (*getsysattr) (TupleTableSlot *slot, int attnum, bool *isnull);
169 :
170 : /*
171 : * Make the contents of the slot solely depend on the slot, and not on
172 : * underlying resources (like another memory context, buffers, etc).
173 : */
174 : void (*materialize) (TupleTableSlot *slot);
175 :
176 : /*
177 : * Copy the contents of the source slot into the destination slot's own
178 : * context. Invoked using callback of the destination slot.
179 : */
180 : void (*copyslot) (TupleTableSlot *dstslot, TupleTableSlot *srcslot);
181 :
182 : /*
183 : * Return a heap tuple "owned" by the slot. It is slot's responsibility to
184 : * free the memory consumed by the heap tuple. If the slot can not "own" a
185 : * heap tuple, it should not implement this callback and should set it as
186 : * NULL.
187 : */
188 : HeapTuple (*get_heap_tuple) (TupleTableSlot *slot);
189 :
190 : /*
191 : * Return a minimal tuple "owned" by the slot. It is slot's responsibility
192 : * to free the memory consumed by the minimal tuple. If the slot can not
193 : * "own" a minimal tuple, it should not implement this callback and should
194 : * set it as NULL.
195 : */
196 : MinimalTuple (*get_minimal_tuple) (TupleTableSlot *slot);
197 :
198 : /*
199 : * Return a copy of heap tuple representing the contents of the slot. The
200 : * copy needs to be palloc'd in the current memory context. The slot
201 : * itself is expected to remain unaffected. It is *not* expected to have
202 : * meaningful "system columns" in the copy. The copy is not be "owned" by
203 : * the slot i.e. the caller has to take responsibility to free memory
204 : * consumed by the slot.
205 : */
206 : HeapTuple (*copy_heap_tuple) (TupleTableSlot *slot);
207 :
208 : /*
209 : * Return a copy of minimal tuple representing the contents of the slot.
210 : * The copy needs to be palloc'd in the current memory context. The slot
211 : * itself is expected to remain unaffected. It is *not* expected to have
212 : * meaningful "system columns" in the copy. The copy is not be "owned" by
213 : * the slot i.e. the caller has to take responsibility to free memory
214 : * consumed by the slot.
215 : */
216 : MinimalTuple (*copy_minimal_tuple) (TupleTableSlot *slot);
217 : };
218 :
219 : /*
220 : * Predefined TupleTableSlotOps for various types of TupleTableSlotOps. The
221 : * same are used to identify the type of a given slot.
222 : */
223 : extern PGDLLIMPORT const TupleTableSlotOps TTSOpsVirtual;
224 : extern PGDLLIMPORT const TupleTableSlotOps TTSOpsHeapTuple;
225 : extern PGDLLIMPORT const TupleTableSlotOps TTSOpsMinimalTuple;
226 : extern PGDLLIMPORT const TupleTableSlotOps TTSOpsBufferHeapTuple;
227 :
228 : #define TTS_IS_VIRTUAL(slot) ((slot)->tts_ops == &TTSOpsVirtual)
229 : #define TTS_IS_HEAPTUPLE(slot) ((slot)->tts_ops == &TTSOpsHeapTuple)
230 : #define TTS_IS_MINIMALTUPLE(slot) ((slot)->tts_ops == &TTSOpsMinimalTuple)
231 : #define TTS_IS_BUFFERTUPLE(slot) ((slot)->tts_ops == &TTSOpsBufferHeapTuple)
232 :
233 :
234 : /*
235 : * Tuple table slot implementations.
236 : */
237 :
238 : typedef struct VirtualTupleTableSlot
239 : {
240 : TupleTableSlot base;
241 :
242 : char *data; /* data for materialized slots */
243 : } VirtualTupleTableSlot;
244 :
245 : typedef struct HeapTupleTableSlot
246 : {
247 : TupleTableSlot base;
248 :
249 : #define FIELDNO_HEAPTUPLETABLESLOT_TUPLE 1
250 : HeapTuple tuple; /* physical tuple */
251 : #define FIELDNO_HEAPTUPLETABLESLOT_OFF 2
252 : uint32 off; /* saved state for slot_deform_heap_tuple */
253 : HeapTupleData tupdata; /* optional workspace for storing tuple */
254 : } HeapTupleTableSlot;
255 :
256 : /* heap tuple residing in a buffer */
257 : typedef struct BufferHeapTupleTableSlot
258 : {
259 : HeapTupleTableSlot base;
260 :
261 : /*
262 : * If buffer is not InvalidBuffer, then the slot is holding a pin on the
263 : * indicated buffer page; drop the pin when we release the slot's
264 : * reference to that buffer. (TTS_FLAG_SHOULDFREE should not be set in
265 : * such a case, since presumably tts_tuple is pointing into the buffer.)
266 : */
267 : Buffer buffer; /* tuple's buffer, or InvalidBuffer */
268 : } BufferHeapTupleTableSlot;
269 :
270 : typedef struct MinimalTupleTableSlot
271 : {
272 : TupleTableSlot base;
273 :
274 : /*
275 : * In a minimal slot tuple points at minhdr and the fields of that struct
276 : * are set correctly for access to the minimal tuple; in particular,
277 : * minhdr.t_data points MINIMAL_TUPLE_OFFSET bytes before mintuple. This
278 : * allows column extraction to treat the case identically to regular
279 : * physical tuples.
280 : */
281 : #define FIELDNO_MINIMALTUPLETABLESLOT_TUPLE 1
282 : HeapTuple tuple; /* tuple wrapper */
283 : MinimalTuple mintuple; /* minimal tuple, or NULL if none */
284 : HeapTupleData minhdr; /* workspace for minimal-tuple-only case */
285 : #define FIELDNO_MINIMALTUPLETABLESLOT_OFF 4
286 : uint32 off; /* saved state for slot_deform_heap_tuple */
287 : } MinimalTupleTableSlot;
288 :
289 : /*
290 : * TupIsNull -- is a TupleTableSlot empty?
291 : */
292 : #define TupIsNull(slot) \
293 : ((slot) == NULL || TTS_EMPTY(slot))
294 :
295 : /* in executor/execTuples.c */
296 : extern TupleTableSlot *MakeTupleTableSlot(TupleDesc tupleDesc,
297 : const TupleTableSlotOps *tts_ops);
298 : extern TupleTableSlot *ExecAllocTableSlot(List **tupleTable, TupleDesc desc,
299 : const TupleTableSlotOps *tts_ops);
300 : extern void ExecResetTupleTable(List *tupleTable, bool shouldFree);
301 : extern TupleTableSlot *MakeSingleTupleTableSlot(TupleDesc tupdesc,
302 : const TupleTableSlotOps *tts_ops);
303 : extern void ExecDropSingleTupleTableSlot(TupleTableSlot *slot);
304 : extern void ExecSetSlotDescriptor(TupleTableSlot *slot, TupleDesc tupdesc);
305 : extern TupleTableSlot *ExecStoreHeapTuple(HeapTuple tuple,
306 : TupleTableSlot *slot,
307 : bool shouldFree);
308 : extern void ExecForceStoreHeapTuple(HeapTuple tuple,
309 : TupleTableSlot *slot,
310 : bool shouldFree);
311 : extern TupleTableSlot *ExecStoreBufferHeapTuple(HeapTuple tuple,
312 : TupleTableSlot *slot,
313 : Buffer buffer);
314 : extern TupleTableSlot *ExecStorePinnedBufferHeapTuple(HeapTuple tuple,
315 : TupleTableSlot *slot,
316 : Buffer buffer);
317 : extern TupleTableSlot *ExecStoreMinimalTuple(MinimalTuple mtup,
318 : TupleTableSlot *slot,
319 : bool shouldFree);
320 : extern void ExecForceStoreMinimalTuple(MinimalTuple mtup, TupleTableSlot *slot,
321 : bool shouldFree);
322 : extern TupleTableSlot *ExecStoreVirtualTuple(TupleTableSlot *slot);
323 : extern TupleTableSlot *ExecStoreAllNullTuple(TupleTableSlot *slot);
324 : extern void ExecStoreHeapTupleDatum(Datum data, TupleTableSlot *slot);
325 : extern HeapTuple ExecFetchSlotHeapTuple(TupleTableSlot *slot, bool materialize, bool *shouldFree);
326 : extern MinimalTuple ExecFetchSlotMinimalTuple(TupleTableSlot *slot,
327 : bool *shouldFree);
328 : extern Datum ExecFetchSlotHeapTupleDatum(TupleTableSlot *slot);
329 : extern void slot_getmissingattrs(TupleTableSlot *slot, int startAttNum,
330 : int lastAttNum);
331 : extern void slot_getsomeattrs_int(TupleTableSlot *slot, int attnum);
332 :
333 :
334 : #ifndef FRONTEND
335 :
336 : /*
337 : * This function forces the entries of the slot's Datum/isnull arrays to be
338 : * valid at least up through the attnum'th entry.
339 : */
340 : static inline void
341 178440468 : slot_getsomeattrs(TupleTableSlot *slot, int attnum)
342 : {
343 178440468 : if (slot->tts_nvalid < attnum)
344 154951558 : slot_getsomeattrs_int(slot, attnum);
345 178440468 : }
346 :
347 : /*
348 : * slot_getallattrs
349 : * This function forces all the entries of the slot's Datum/isnull
350 : * arrays to be valid. The caller may then extract data directly
351 : * from those arrays instead of using slot_getattr.
352 : */
353 : static inline void
354 6594970 : slot_getallattrs(TupleTableSlot *slot)
355 : {
356 6594970 : slot_getsomeattrs(slot, slot->tts_tupleDescriptor->natts);
357 6594970 : }
358 :
359 :
360 : /*
361 : * slot_attisnull
362 : *
363 : * Detect whether an attribute of the slot is null, without actually fetching
364 : * it.
365 : */
366 : static inline bool
367 24002118 : slot_attisnull(TupleTableSlot *slot, int attnum)
368 : {
369 : AssertArg(attnum > 0);
370 :
371 24002118 : if (attnum > slot->tts_nvalid)
372 22963270 : slot_getsomeattrs(slot, attnum);
373 :
374 24002118 : return slot->tts_isnull[attnum - 1];
375 : }
376 :
377 : /*
378 : * slot_getattr - fetch one attribute of the slot's contents.
379 : */
380 : static inline Datum
381 90256924 : slot_getattr(TupleTableSlot *slot, int attnum,
382 : bool *isnull)
383 : {
384 : AssertArg(attnum > 0);
385 :
386 90256924 : if (attnum > slot->tts_nvalid)
387 55882288 : slot_getsomeattrs(slot, attnum);
388 :
389 90256924 : *isnull = slot->tts_isnull[attnum - 1];
390 :
391 90256924 : return slot->tts_values[attnum - 1];
392 : }
393 :
394 : /*
395 : * slot_getsysattr - fetch a system attribute of the slot's current tuple.
396 : *
397 : * If the slot type does not contain system attributes, this will throw an
398 : * error. Hence before calling this function, callers should make sure that
399 : * the slot type is the one that supports system attributes.
400 : */
401 : static inline Datum
402 5374138 : slot_getsysattr(TupleTableSlot *slot, int attnum, bool *isnull)
403 : {
404 : AssertArg(attnum < 0); /* caller error */
405 :
406 5374138 : if (attnum == TableOidAttributeNumber)
407 : {
408 3116818 : *isnull = false;
409 3116818 : return ObjectIdGetDatum(slot->tts_tableOid);
410 : }
411 2257320 : else if (attnum == SelfItemPointerAttributeNumber)
412 : {
413 2256500 : *isnull = false;
414 2256500 : return PointerGetDatum(&slot->tts_tid);
415 : }
416 :
417 : /* Fetch the system attribute from the underlying tuple. */
418 820 : return slot->tts_ops->getsysattr(slot, attnum, isnull);
419 : }
420 :
421 : /*
422 : * ExecClearTuple - clear the slot's contents
423 : */
424 : static inline TupleTableSlot *
425 112361874 : ExecClearTuple(TupleTableSlot *slot)
426 : {
427 112361874 : slot->tts_ops->clear(slot);
428 :
429 112361874 : return slot;
430 : }
431 :
432 : /* ExecMaterializeSlot - force a slot into the "materialized" state.
433 : *
434 : * This causes the slot's tuple to be a local copy not dependent on any
435 : * external storage (i.e. pointing into a Buffer, or having allocations in
436 : * another memory context).
437 : *
438 : * A typical use for this operation is to prepare a computed tuple for being
439 : * stored on disk. The original data may or may not be virtual, but in any
440 : * case we need a private copy for heap_insert to scribble on.
441 : */
442 : static inline void
443 13435820 : ExecMaterializeSlot(TupleTableSlot *slot)
444 : {
445 13435820 : slot->tts_ops->materialize(slot);
446 13435820 : }
447 :
448 : /*
449 : * ExecCopySlotHeapTuple - return HeapTuple allocated in caller's context
450 : */
451 : static inline HeapTuple
452 28609126 : ExecCopySlotHeapTuple(TupleTableSlot *slot)
453 : {
454 : Assert(!TTS_EMPTY(slot));
455 :
456 28609126 : return slot->tts_ops->copy_heap_tuple(slot);
457 : }
458 :
459 : /*
460 : * ExecCopySlotMinimalTuple - return MinimalTuple allocated in caller's context
461 : */
462 : static inline MinimalTuple
463 9986538 : ExecCopySlotMinimalTuple(TupleTableSlot *slot)
464 : {
465 9986538 : return slot->tts_ops->copy_minimal_tuple(slot);
466 : }
467 :
468 : /*
469 : * ExecCopySlot - copy one slot's contents into another.
470 : *
471 : * If a source's system attributes are supposed to be accessed in the target
472 : * slot, the target slot and source slot types need to match.
473 : */
474 : static inline TupleTableSlot *
475 12049936 : ExecCopySlot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
476 : {
477 : Assert(!TTS_EMPTY(srcslot));
478 : AssertArg(srcslot != dstslot);
479 :
480 12049936 : dstslot->tts_ops->copyslot(dstslot, srcslot);
481 :
482 12049936 : return dstslot;
483 : }
484 :
485 : #endif /* FRONTEND */
486 :
487 : #endif /* TUPTABLE_H */
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