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Diffstat (limited to 'src/include/executor/tuptable.h')
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diff --git a/src/include/executor/tuptable.h b/src/include/executor/tuptable.h new file mode 100644 index 0000000..f7df70b --- /dev/null +++ b/src/include/executor/tuptable.h @@ -0,0 +1,487 @@ +/*------------------------------------------------------------------------- + * + * tuptable.h + * tuple table support stuff + * + * + * Portions Copyright (c) 1996-2020, 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". + * (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. 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_SHOULDFREE should not be set in tts_flags, tts_tuple + * must be NULL 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. + * + * 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 +{ + TupleTableSlot base; + + char *data; /* data for materialized slots */ +} VirtualTupleTableSlot; + +typedef struct HeapTupleTableSlot +{ + 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 +{ + 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 tts_tuple is pointing into the buffer.) + */ + Buffer buffer; /* tuple's buffer, or InvalidBuffer */ +} BufferHeapTupleTableSlot; + +typedef struct MinimalTupleTableSlot +{ + 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) +{ + AssertArg(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) +{ + AssertArg(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) +{ + AssertArg(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)); + AssertArg(srcslot != dstslot); + + dstslot->tts_ops->copyslot(dstslot, srcslot); + + return dstslot; +} + +#endif /* FRONTEND */ + +#endif /* TUPTABLE_H */ |