postgresql/src/include/executor/tuptable.h

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/*-------------------------------------------------------------------------
*
* tuptable.h
* tuple table support stuff
*
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
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* src/include/executor/tuptable.h
*
*-------------------------------------------------------------------------
*/
#ifndef TUPTABLE_H
#define TUPTABLE_H
#include "access/htup.h"
#include "access/tupdesc.h"
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#include "storage/buf.h"
/*----------
* The executor stores tuples in a "tuple table" which is a List of
* independent TupleTableSlots. There are several cases we need to handle:
* 1. physical tuple in a disk buffer page
* 2. physical tuple constructed in palloc'ed memory
* 3. "minimal" physical tuple constructed in palloc'ed memory
* 4. "virtual" tuple consisting of Datum/isnull arrays
*
* The first two cases are similar in that they both deal with "materialized"
* tuples, but resource management is different. For a tuple in a disk page
* we need to hold a pin on the buffer until the TupleTableSlot's reference
* to the tuple is dropped; while for a palloc'd tuple we usually want the
* tuple pfree'd when the TupleTableSlot's reference is dropped.
*
* A "minimal" tuple is handled similarly to a palloc'd regular tuple.
* At present, minimal tuples never are stored in buffers, so there is no
* parallel to case 1. Note that a minimal tuple has no "system columns".
* (Actually, it could have an OID, but we have no need to access the OID.)
*
* A "virtual" tuple is an optimization used to minimize physical data
* copying in a nest of plan nodes. Any pass-by-reference Datums in the
* tuple point to storage that is not directly associated with the
* TupleTableSlot; generally they will point to part of a tuple stored in
* a lower plan node's output TupleTableSlot, or to a function result
* constructed in a plan node's per-tuple econtext. It is the responsibility
* of the generating plan node to be sure these resources are not released
* for as long as the virtual tuple needs to be valid. We only use virtual
* tuples in the result slots of plan nodes --- tuples to be copied anywhere
* else need to be "materialized" into physical tuples. Note also that a
* virtual tuple does not have any "system columns".
*
* It is also possible for a TupleTableSlot to hold both physical and minimal
* copies of a tuple. This is done when the slot is requested to provide
* the format other than the one it currently holds. (Originally we attempted
* to handle such requests by replacing one format with the other, but that
* had the fatal defect of invalidating any pass-by-reference Datums pointing
* into the existing slot contents.) Both copies must contain identical data
* payloads when this is the case.
*
* The Datum/isnull arrays of a TupleTableSlot serve double duty. When the
* slot contains a virtual tuple, they are the authoritative data. When the
* slot contains a physical tuple, the arrays contain data extracted from
* the tuple. (In this state, any pass-by-reference Datums point into
* the physical tuple.) The extracted information is built "lazily",
* ie, only as needed. This serves to avoid repeated extraction of data
* from the physical tuple.
*
* A TupleTableSlot can also be "empty", indicated by flag TTS_EMPTY set in
* tts_flags, holding no valid data. This is the only valid state for a
* freshly-created slot that has not yet had a tuple descriptor assigned to it.
* In this state, TTS_SHOULDFREE should not be set in tts_flag, tts_tuple must
* be NULL, tts_buffer InvalidBuffer, and tts_nvalid zero.
*
* The tupleDescriptor is simply referenced, not copied, by the TupleTableSlot
* code. The caller of ExecSetSlotDescriptor() is responsible for providing
* a descriptor that will live as long as the slot does. (Typically, both
* slots and descriptors are in per-query memory and are freed by memory
* context deallocation at query end; so it's not worth providing any extra
* mechanism to do more. However, the slot will increment the tupdesc
* reference count if a reference-counted tupdesc is supplied.)
*
* When TTS_SHOULDFREE is set in tts_flags, the physical tuple is "owned" by
* the slot and should be freed when the slot's reference to the tuple is
* dropped.
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*
* If tts_buffer is not InvalidBuffer, then the slot is holding a pin
* on the indicated buffer page; drop the pin when we release the
* slot's reference to that buffer. (tts_shouldFree should always be
* false in such a case, since presumably tts_tuple is pointing at the
* buffer page.)
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*
* tts_nvalid indicates the number of valid columns in the tts_values/isnull
* arrays. When the slot is holding a "virtual" tuple this must be equal
* to the descriptor's natts. When the slot is holding a physical tuple
* this is equal to the number of columns we have extracted (we always
* extract columns from left to right, so there are no holes).
*
* tts_values/tts_isnull are allocated when a descriptor is assigned to the
* slot; they are of length equal to the descriptor's natts.
*
* tts_mintuple must always be NULL if the slot does not hold a "minimal"
* tuple. When it does, tts_mintuple points to the actual MinimalTupleData
* object (the thing to be pfree'd if tts_shouldFreeMin is true). If the slot
* has only a minimal and not also a regular physical tuple, then tts_tuple
* points at tts_minhdr and the fields of that struct are set correctly
* for access to the minimal tuple; in particular, tts_minhdr.t_data points
* MINIMAL_TUPLE_OFFSET bytes before tts_mintuple. This allows column
* extraction to treat the case identically to regular physical tuples.
*
* TTS_SLOW flag in tts_flags and tts_off are saved state for
* slot_deform_tuple, and should not be touched by any other code.
*----------
*/
/* true = slot is empty */
#define TTS_FLAG_EMPTY (1 << 1)
#define TTS_EMPTY(slot) (((slot)->tts_flags & TTS_FLAG_EMPTY) != 0)
/* should pfree tts_tuple? */
#define TTS_FLAG_SHOULDFREE (1 << 2)
#define TTS_SHOULDFREE(slot) (((slot)->tts_flags & TTS_FLAG_SHOULDFREE) != 0)
/* should pfree tts_mintuple? */
#define TTS_FLAG_SHOULDFREEMIN (1 << 3)
#define TTS_SHOULDFREEMIN(slot) (((slot)->tts_flags & TTS_FLAG_SHOULDFREEMIN) != 0)
/* saved state for slot_deform_tuple */
#define TTS_FLAG_SLOW (1 << 4)
#define TTS_SLOW(slot) (((slot)->tts_flags & TTS_FLAG_SLOW) != 0)
/* fixed tuple descriptor */
#define TTS_FLAG_FIXED (1 << 5)
#define TTS_FIXED(slot) (((slot)->tts_flags & TTS_FLAG_FIXED) != 0)
typedef struct TupleTableSlot
{
NodeTag type;
#define FIELDNO_TUPLETABLESLOT_FLAGS 1
uint16 tts_flags; /* Boolean states */
#define FIELDNO_TUPLETABLESLOT_NVALID 2
AttrNumber tts_nvalid; /* # of valid values in tts_values */
#define FIELDNO_TUPLETABLESLOT_TUPLE 3
HeapTuple tts_tuple; /* physical tuple, or NULL if virtual */
#define FIELDNO_TUPLETABLESLOT_TUPLEDESCRIPTOR 4
TupleDesc tts_tupleDescriptor; /* slot's tuple descriptor */
MemoryContext tts_mcxt; /* slot itself is in this context */
Buffer tts_buffer; /* tuple's buffer, or InvalidBuffer */
#define FIELDNO_TUPLETABLESLOT_OFF 7
uint32 tts_off; /* saved state for slot_deform_tuple */
#define FIELDNO_TUPLETABLESLOT_VALUES 8
Datum *tts_values; /* current per-attribute values */
#define FIELDNO_TUPLETABLESLOT_ISNULL 9
bool *tts_isnull; /* current per-attribute isnull flags */
MinimalTuple tts_mintuple; /* minimal tuple, or NULL if none */
HeapTupleData tts_minhdr; /* workspace for minimal-tuple-only case */
} TupleTableSlot;
#define TTS_HAS_PHYSICAL_TUPLE(slot) \
((slot)->tts_tuple != NULL && (slot)->tts_tuple != &((slot)->tts_minhdr))
/*
* TupIsNull -- is a TupleTableSlot empty?
*/
#define TupIsNull(slot) \
((slot) == NULL || TTS_EMPTY(slot))
/* in executor/execTuples.c */
extern TupleTableSlot *MakeTupleTableSlot(TupleDesc desc);
extern TupleTableSlot *ExecAllocTableSlot(List **tupleTable, TupleDesc desc);
extern void ExecResetTupleTable(List *tupleTable, bool shouldFree);
extern TupleTableSlot *MakeSingleTupleTableSlot(TupleDesc tupdesc);
extern void ExecDropSingleTupleTableSlot(TupleTableSlot *slot);
extern void ExecSetSlotDescriptor(TupleTableSlot *slot, TupleDesc tupdesc);
extern TupleTableSlot *ExecStoreHeapTuple(HeapTuple tuple,
TupleTableSlot *slot,
bool shouldFree);
extern TupleTableSlot *ExecStoreBufferHeapTuple(HeapTuple tuple,
TupleTableSlot *slot,
Buffer buffer);
extern TupleTableSlot *ExecStoreMinimalTuple(MinimalTuple mtup,
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TupleTableSlot *slot,
bool shouldFree);
extern TupleTableSlot *ExecClearTuple(TupleTableSlot *slot);
extern TupleTableSlot *ExecStoreVirtualTuple(TupleTableSlot *slot);
extern TupleTableSlot *ExecStoreAllNullTuple(TupleTableSlot *slot);
extern HeapTuple ExecCopySlotTuple(TupleTableSlot *slot);
extern MinimalTuple ExecCopySlotMinimalTuple(TupleTableSlot *slot);
extern HeapTuple ExecFetchSlotHeapTuple(TupleTableSlot *slot, bool materialize, bool *shoulFree);
extern MinimalTuple ExecFetchSlotMinimalTuple(TupleTableSlot *slot,
bool *shouldFree);
extern Datum ExecFetchSlotHeapTupleDatum(TupleTableSlot *slot);
extern void ExecMaterializeSlot(TupleTableSlot *slot);
extern TupleTableSlot *ExecCopySlot(TupleTableSlot *dstslot,
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TupleTableSlot *srcslot);
extern void slot_getmissingattrs(TupleTableSlot *slot, int startAttNum,
int lastAttNum);
extern Datum slot_getattr(TupleTableSlot *slot, int attnum,
bool *isnull);
extern void slot_getsomeattrs(TupleTableSlot *slot, int attnum);
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/* in access/common/heaptuple.c */
extern bool slot_attisnull(TupleTableSlot *slot, int attnum);
extern bool slot_getsysattr(TupleTableSlot *slot, int attnum,
Datum *value, bool *isnull);
extern Datum getmissingattr(TupleDesc tupleDesc,
int attnum, bool *isnull);
#ifndef FRONTEND
/*
* slot_getallattrs
* This function forces all the entries of the slot's Datum/isnull
* arrays to be valid. The caller may then extract data directly
* from those arrays instead of using slot_getattr.
*/
static inline void
slot_getallattrs(TupleTableSlot *slot)
{
slot_getsomeattrs(slot, slot->tts_tupleDescriptor->natts);
}
#endif
Phase 2 of pgindent updates. Change pg_bsd_indent to follow upstream rules for placement of comments to the right of code, and remove pgindent hack that caused comments following #endif to not obey the general rule. Commit e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 wasn't actually using the published version of pg_bsd_indent, but a hacked-up version that tried to minimize the amount of movement of comments to the right of code. The situation of interest is where such a comment has to be moved to the right of its default placement at column 33 because there's code there. BSD indent has always moved right in units of tab stops in such cases --- but in the previous incarnation, indent was working in 8-space tab stops, while now it knows we use 4-space tabs. So the net result is that in about half the cases, such comments are placed one tab stop left of before. This is better all around: it leaves more room on the line for comment text, and it means that in such cases the comment uniformly starts at the next 4-space tab stop after the code, rather than sometimes one and sometimes two tabs after. Also, ensure that comments following #endif are indented the same as comments following other preprocessor commands such as #else. That inconsistency turns out to have been self-inflicted damage from a poorly-thought-through post-indent "fixup" in pgindent. This patch is much less interesting than the first round of indent changes, but also bulkier, so I thought it best to separate the effects. Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
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#endif /* TUPTABLE_H */