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/*------------------------------------------------------------------------- * * htup.h * POSTGRES heap tuple definitions. * * * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/include/access/htup.h * *------------------------------------------------------------------------- */ #ifndef HTUP_H #define HTUP_H #include "storage/itemptr.h" /* typedefs and forward declarations for structs defined in htup_details.h */ typedef struct HeapTupleHeaderData HeapTupleHeaderData; typedef HeapTupleHeaderData *HeapTupleHeader; typedef struct MinimalTupleData MinimalTupleData; typedef MinimalTupleData *MinimalTuple; /* * HeapTupleData is an in-memory data structure that points to a tuple. * * There are several ways in which this data structure is used: * * * Pointer to a tuple in a disk buffer: t_data points directly into the * buffer (which the code had better be holding a pin on, but this is not * reflected in HeapTupleData itself). * * * Pointer to nothing: t_data is NULL. This is used as a failure indication * in some functions. * * * Part of a palloc'd tuple: the HeapTupleData itself and the tuple * form a single palloc'd chunk. t_data points to the memory location * immediately following the HeapTupleData struct (at offset HEAPTUPLESIZE). * This is the output format of heap_form_tuple and related routines. * * * Separately allocated tuple: t_data points to a palloc'd chunk that * is not adjacent to the HeapTupleData. (This case is deprecated since * it's difficult to tell apart from case #1. It should be used only in * limited contexts where the code knows that case #1 will never apply.) * * * Separately allocated minimal tuple: t_data points MINIMAL_TUPLE_OFFSET * bytes before the start of a MinimalTuple. As with the previous case, * this can't be told apart from case #1 by inspection; code setting up * or destroying this representation has to know what it's doing. * * t_len should always be valid, except in the pointer-to-nothing case. * t_self and t_tableOid should be valid if the HeapTupleData points to * a disk buffer, or if it represents a copy of a tuple on disk. They * should be explicitly set invalid in manufactured tuples. */ typedef struct HeapTupleData { uint32 t_len; /* length of *t_data */ ItemPointerData t_self; /* SelfItemPointer */ Oid t_tableOid; /* table the tuple came from */ HeapTupleHeader t_data; /* -> tuple header and data */ } HeapTupleData; typedef HeapTupleData *HeapTuple; #define HEAPTUPLESIZE MAXALIGN(sizeof(HeapTupleData)) /* * Accessor macros to be used with HeapTuple pointers. */ #define HeapTupleIsValid(tuple) PointerIsValid(tuple) /* HeapTupleHeader functions implemented in utils/time/combocid.c */ extern CommandId HeapTupleHeaderGetCmin(HeapTupleHeader tup); extern CommandId HeapTupleHeaderGetCmax(HeapTupleHeader tup); extern void HeapTupleHeaderAdjustCmax(HeapTupleHeader tup, CommandId *cmax, bool *iscombo); /* Prototype for HeapTupleHeader accessors in heapam.c */ extern TransactionId HeapTupleGetUpdateXid(HeapTupleHeader tuple); #endif /* HTUP_H */