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/*-------------------------------------------------------------------------
*
* tuptable.h
* tuple table support stuff
*
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/executor/tuptable.h
*
*-------------------------------------------------------------------------
*/
#ifndef TUPTABLE_H
#define TUPTABLE_H
#include "access/htup.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/tupdesc.h"
#include "storage/buf.h"
/*----------
* The executor stores tuples in a "tuple table" which is a List of
* independent TupleTableSlots.
*
* There's various different types of tuple table slots, each being able to
* store different types of tuples. Additional types of slots can be added
* without modifying core code. The type of a slot is determined by the
* TupleTableSlotOps* passed to the slot creation routine. The builtin types
* of slots are
*
* 1. physical tuple in a disk buffer page (TTSOpsBufferHeapTuple)
* 2. physical tuple constructed in palloc'ed memory (TTSOpsHeapTuple)
* 3. "minimal" physical tuple constructed in palloc'ed memory
* (TTSOpsMinimalTuple)
* 4. "virtual" tuple consisting of Datum/isnull arrays (TTSOpsVirtual)
*
*
* 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".
*
* A "virtual" tuple is an optimization used to minimize physical data copying
* in a nest of plan nodes. Until materialized pass-by-reference Datums in
* the slot 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 or is materialized. Note
* also that a virtual tuple does not have any "system columns".
*
* The Datum/isnull arrays of a TupleTableSlot serve double duty. For virtual
* slots they are the authoritative data. For the other builtin slots,
* 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_FLAG_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_FLAG_SHOULDFREE should not be set in tts_flags and
* tts_nvalid should be set to 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_FLAG_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.
*
* tts_values/tts_isnull are allocated either when the slot is created (when
* the descriptor is provided), or when a descriptor is assigned to the slot;
* they are of length equal to the descriptor's natts.
*
* The TTS_FLAG_SLOW flag is saved state for
* slot_deform_heap_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 tuple "owned" by the slot? */
#define TTS_FLAG_SHOULDFREE (1 << 2)
#define TTS_SHOULDFREE(slot) (((slot)->tts_flags & TTS_FLAG_SHOULDFREE) != 0)
/* saved state for slot_deform_heap_tuple */
#define TTS_FLAG_SLOW (1 << 3)
#define TTS_SLOW(slot) (((slot)->tts_flags & TTS_FLAG_SLOW) != 0)
/* fixed tuple descriptor */
#define TTS_FLAG_FIXED (1 << 4)
#define TTS_FIXED(slot) (((slot)->tts_flags & TTS_FLAG_FIXED) != 0)
struct TupleTableSlotOps;
typedef struct TupleTableSlotOps TupleTableSlotOps;
/* base tuple table slot type */
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 */
const TupleTableSlotOps *const tts_ops; /* implementation of slot */
#define FIELDNO_TUPLETABLESLOT_TUPLEDESCRIPTOR 4
TupleDesc tts_tupleDescriptor; /* slot's tuple descriptor */
#define FIELDNO_TUPLETABLESLOT_VALUES 5
Datum *tts_values; /* current per-attribute values */
#define FIELDNO_TUPLETABLESLOT_ISNULL 6
bool *tts_isnull; /* current per-attribute isnull flags */
MemoryContext tts_mcxt; /* slot itself is in this context */
ItemPointerData tts_tid; /* stored tuple's tid */
Oid tts_tableOid; /* table oid of tuple */
} TupleTableSlot;
/* routines for a TupleTableSlot implementation */
struct TupleTableSlotOps
{
/* Minimum size of the slot */
size_t base_slot_size;
/* Initialization. */
void (*init) (TupleTableSlot *slot);
/* Destruction. */
void (*release) (TupleTableSlot *slot);
/*
* Clear the contents of the slot. Only the contents are expected to be
* cleared and not the tuple descriptor. Typically an implementation of
* this callback should free the memory allocated for the tuple contained
* in the slot.
*/
void (*clear) (TupleTableSlot *slot);
/*
* Fill up first natts entries of tts_values and tts_isnull arrays with
* values from the tuple contained in the slot. The function may be called
* with natts more than the number of attributes available in the tuple,
* in which case it should set tts_nvalid to the number of returned
* columns.
*/
void (*getsomeattrs) (TupleTableSlot *slot, int natts);
/*
* Returns value of the given system attribute as a datum and sets isnull
* to false, if it's not NULL. Throws an error if the slot type does not
* support system attributes.
*/
Datum (*getsysattr) (TupleTableSlot *slot, int attnum, bool *isnull);
/*
* Make the contents of the slot solely depend on the slot, and not on
* underlying resources (like another memory context, buffers, etc).
*/
void (*materialize) (TupleTableSlot *slot);
/*
* Copy the contents of the source slot into the destination slot's own
* context. Invoked using callback of the destination slot.
*/
void (*copyslot) (TupleTableSlot *dstslot, TupleTableSlot *srcslot);
/*
* Return a heap tuple "owned" by the slot. It is slot's responsibility to
* free the memory consumed by the heap tuple. If the slot can not "own" a
* heap tuple, it should not implement this callback and should set it as
* NULL.
*/
HeapTuple (*get_heap_tuple) (TupleTableSlot *slot);
/*
* Return a minimal tuple "owned" by the slot. It is slot's responsibility
* to free the memory consumed by the minimal tuple. If the slot can not
* "own" a minimal tuple, it should not implement this callback and should
* set it as NULL.
*/
MinimalTuple (*get_minimal_tuple) (TupleTableSlot *slot);
/*
* Return a copy of heap tuple representing the contents of the slot. The
* copy needs to be palloc'd in the current memory context. The slot
* itself is expected to remain unaffected. It is *not* expected to have
* meaningful "system columns" in the copy. The copy is not be "owned" by
* the slot i.e. the caller has to take responsibility to free memory
* consumed by the slot.
*/
HeapTuple (*copy_heap_tuple) (TupleTableSlot *slot);
/*
* Return a copy of minimal tuple representing the contents of the slot.
* The copy needs to be palloc'd in the current memory context. The slot
* itself is expected to remain unaffected. It is *not* expected to have
* meaningful "system columns" in the copy. The copy is not be "owned" by
* the slot i.e. the caller has to take responsibility to free memory
* consumed by the slot.
*/
MinimalTuple (*copy_minimal_tuple) (TupleTableSlot *slot);
};
/*
* Predefined TupleTableSlotOps for various types of TupleTableSlotOps. The
* same are used to identify the type of a given slot.
*/
extern PGDLLIMPORT const TupleTableSlotOps TTSOpsVirtual;
extern PGDLLIMPORT const TupleTableSlotOps TTSOpsHeapTuple;
extern PGDLLIMPORT const TupleTableSlotOps TTSOpsMinimalTuple;
extern PGDLLIMPORT const TupleTableSlotOps TTSOpsBufferHeapTuple;
#define TTS_IS_VIRTUAL(slot) ((slot)->tts_ops == &TTSOpsVirtual)
#define TTS_IS_HEAPTUPLE(slot) ((slot)->tts_ops == &TTSOpsHeapTuple)
#define TTS_IS_MINIMALTUPLE(slot) ((slot)->tts_ops == &TTSOpsMinimalTuple)
#define TTS_IS_BUFFERTUPLE(slot) ((slot)->tts_ops == &TTSOpsBufferHeapTuple)
/*
* Tuple table slot implementations.
*/
typedef struct VirtualTupleTableSlot
{
pg_node_attr(abstract)
TupleTableSlot base;
char *data; /* data for materialized slots */
} VirtualTupleTableSlot;
typedef struct HeapTupleTableSlot
{
pg_node_attr(abstract)
TupleTableSlot base;
#define FIELDNO_HEAPTUPLETABLESLOT_TUPLE 1
HeapTuple tuple; /* physical tuple */
#define FIELDNO_HEAPTUPLETABLESLOT_OFF 2
uint32 off; /* saved state for slot_deform_heap_tuple */
HeapTupleData tupdata; /* optional workspace for storing tuple */
} HeapTupleTableSlot;
/* heap tuple residing in a buffer */
typedef struct BufferHeapTupleTableSlot
{
pg_node_attr(abstract)
HeapTupleTableSlot base;
/*
* If 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_FLAG_SHOULDFREE should not be set in
* such a case, since presumably base.tuple is pointing into the buffer.)
*/
Buffer buffer; /* tuple's buffer, or InvalidBuffer */
} BufferHeapTupleTableSlot;
typedef struct MinimalTupleTableSlot
{
pg_node_attr(abstract)
TupleTableSlot base;
/*
* In a minimal slot tuple points at minhdr and the fields of that struct
* are set correctly for access to the minimal tuple; in particular,
* minhdr.t_data points MINIMAL_TUPLE_OFFSET bytes before mintuple. This
* allows column extraction to treat the case identically to regular
* physical tuples.
*/
#define FIELDNO_MINIMALTUPLETABLESLOT_TUPLE 1
HeapTuple tuple; /* tuple wrapper */
MinimalTuple mintuple; /* minimal tuple, or NULL if none */
HeapTupleData minhdr; /* workspace for minimal-tuple-only case */
#define FIELDNO_MINIMALTUPLETABLESLOT_OFF 4
uint32 off; /* saved state for slot_deform_heap_tuple */
} MinimalTupleTableSlot;
/*
* TupIsNull -- is a TupleTableSlot empty?
*/
#define TupIsNull(slot) \
((slot) == NULL || TTS_EMPTY(slot))
/* in executor/execTuples.c */
extern TupleTableSlot *MakeTupleTableSlot(TupleDesc tupleDesc,
const TupleTableSlotOps *tts_ops);
extern TupleTableSlot *ExecAllocTableSlot(List **tupleTable, TupleDesc desc,
const TupleTableSlotOps *tts_ops);
extern void ExecResetTupleTable(List *tupleTable, bool shouldFree);
extern TupleTableSlot *MakeSingleTupleTableSlot(TupleDesc tupdesc,
const TupleTableSlotOps *tts_ops);
extern void ExecDropSingleTupleTableSlot(TupleTableSlot *slot);
extern void ExecSetSlotDescriptor(TupleTableSlot *slot, TupleDesc tupdesc);
extern TupleTableSlot *ExecStoreHeapTuple(HeapTuple tuple,
TupleTableSlot *slot,
bool shouldFree);
extern void ExecForceStoreHeapTuple(HeapTuple tuple,
TupleTableSlot *slot,
bool shouldFree);
extern TupleTableSlot *ExecStoreBufferHeapTuple(HeapTuple tuple,
TupleTableSlot *slot,
Buffer buffer);
extern TupleTableSlot *ExecStorePinnedBufferHeapTuple(HeapTuple tuple,
TupleTableSlot *slot,
Buffer buffer);
extern TupleTableSlot *ExecStoreMinimalTuple(MinimalTuple mtup,
TupleTableSlot *slot,
bool shouldFree);
extern void ExecForceStoreMinimalTuple(MinimalTuple mtup, TupleTableSlot *slot,
bool shouldFree);
extern TupleTableSlot *ExecStoreVirtualTuple(TupleTableSlot *slot);
extern TupleTableSlot *ExecStoreAllNullTuple(TupleTableSlot *slot);
extern void ExecStoreHeapTupleDatum(Datum data, TupleTableSlot *slot);
extern HeapTuple ExecFetchSlotHeapTuple(TupleTableSlot *slot, bool materialize, bool *shouldFree);
extern MinimalTuple ExecFetchSlotMinimalTuple(TupleTableSlot *slot,
bool *shouldFree);
extern Datum ExecFetchSlotHeapTupleDatum(TupleTableSlot *slot);
extern void slot_getmissingattrs(TupleTableSlot *slot, int startAttNum,
int lastAttNum);
extern void slot_getsomeattrs_int(TupleTableSlot *slot, int attnum);
#ifndef FRONTEND
/*
* This function forces the entries of the slot's Datum/isnull arrays to be
* valid at least up through the attnum'th entry.
*/
static inline void
slot_getsomeattrs(TupleTableSlot *slot, int attnum)
{
if (slot->tts_nvalid < attnum)
slot_getsomeattrs_int(slot, attnum);
}
/*
* 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);
}
/*
* slot_attisnull
*
* Detect whether an attribute of the slot is null, without actually fetching
* it.
*/
static inline bool
slot_attisnull(TupleTableSlot *slot, int attnum)
{
Assert(attnum > 0);
if (attnum > slot->tts_nvalid)
slot_getsomeattrs(slot, attnum);
return slot->tts_isnull[attnum - 1];
}
/*
* slot_getattr - fetch one attribute of the slot's contents.
*/
static inline Datum
slot_getattr(TupleTableSlot *slot, int attnum,
bool *isnull)
{
Assert(attnum > 0);
if (attnum > slot->tts_nvalid)
slot_getsomeattrs(slot, attnum);
*isnull = slot->tts_isnull[attnum - 1];
return slot->tts_values[attnum - 1];
}
/*
* slot_getsysattr - fetch a system attribute of the slot's current tuple.
*
* If the slot type does not contain system attributes, this will throw an
* error. Hence before calling this function, callers should make sure that
* the slot type is the one that supports system attributes.
*/
static inline Datum
slot_getsysattr(TupleTableSlot *slot, int attnum, bool *isnull)
{
Assert(attnum < 0); /* caller error */
if (attnum == TableOidAttributeNumber)
{
*isnull = false;
return ObjectIdGetDatum(slot->tts_tableOid);
}
else if (attnum == SelfItemPointerAttributeNumber)
{
*isnull = false;
return PointerGetDatum(&slot->tts_tid);
}
/* Fetch the system attribute from the underlying tuple. */
return slot->tts_ops->getsysattr(slot, attnum, isnull);
}
/*
* ExecClearTuple - clear the slot's contents
*/
static inline TupleTableSlot *
ExecClearTuple(TupleTableSlot *slot)
{
slot->tts_ops->clear(slot);
return slot;
}
/* ExecMaterializeSlot - force a slot into the "materialized" state.
*
* This causes the slot's tuple to be a local copy not dependent on any
* external storage (i.e. pointing into a Buffer, or having allocations in
* another memory context).
*
* A typical use for this operation is to prepare a computed tuple for being
* stored on disk. The original data may or may not be virtual, but in any
* case we need a private copy for heap_insert to scribble on.
*/
static inline void
ExecMaterializeSlot(TupleTableSlot *slot)
{
slot->tts_ops->materialize(slot);
}
/*
* ExecCopySlotHeapTuple - return HeapTuple allocated in caller's context
*/
static inline HeapTuple
ExecCopySlotHeapTuple(TupleTableSlot *slot)
{
Assert(!TTS_EMPTY(slot));
return slot->tts_ops->copy_heap_tuple(slot);
}
/*
* ExecCopySlotMinimalTuple - return MinimalTuple allocated in caller's context
*/
static inline MinimalTuple
ExecCopySlotMinimalTuple(TupleTableSlot *slot)
{
return slot->tts_ops->copy_minimal_tuple(slot);
}
/*
* ExecCopySlot - copy one slot's contents into another.
*
* If a source's system attributes are supposed to be accessed in the target
* slot, the target slot and source slot types need to match.
*/
static inline TupleTableSlot *
ExecCopySlot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
{
Assert(!TTS_EMPTY(srcslot));
Assert(srcslot != dstslot);
dstslot->tts_ops->copyslot(dstslot, srcslot);
return dstslot;
}
#endif /* FRONTEND */
#endif /* TUPTABLE_H */