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7ced1d1247
For any interesting JIT target, fields inside structs need to be
accessed. b96d550e contains infrastructure for syncing the definition
of types between postgres C code and runtime code generation with
LLVM. But that doesn't sync the number or names of fields inside
structs, just the types (including padding etc).
One option would be to hardcode the offset numbers in the JIT code,
but that'd be hard to keep in sync. Instead add macros indicating the
field offset to the fields that need to be accessed. Not pretty, but
manageable.
Author: Andres Freund
Discussion: https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de
90 lines
3.2 KiB
C
90 lines
3.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* htup.h
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* POSTGRES heap tuple definitions.
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*
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*
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* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/access/htup.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef HTUP_H
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#define HTUP_H
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#include "storage/itemptr.h"
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/* typedefs and forward declarations for structs defined in htup_details.h */
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typedef struct HeapTupleHeaderData HeapTupleHeaderData;
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typedef HeapTupleHeaderData *HeapTupleHeader;
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typedef struct MinimalTupleData MinimalTupleData;
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typedef MinimalTupleData *MinimalTuple;
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/*
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* HeapTupleData is an in-memory data structure that points to a tuple.
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*
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* There are several ways in which this data structure is used:
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*
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* * Pointer to a tuple in a disk buffer: t_data points directly into the
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* buffer (which the code had better be holding a pin on, but this is not
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* reflected in HeapTupleData itself).
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*
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* * Pointer to nothing: t_data is NULL. This is used as a failure indication
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* in some functions.
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*
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* * Part of a palloc'd tuple: the HeapTupleData itself and the tuple
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* form a single palloc'd chunk. t_data points to the memory location
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* immediately following the HeapTupleData struct (at offset HEAPTUPLESIZE).
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* This is the output format of heap_form_tuple and related routines.
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*
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* * Separately allocated tuple: t_data points to a palloc'd chunk that
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* is not adjacent to the HeapTupleData. (This case is deprecated since
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* it's difficult to tell apart from case #1. It should be used only in
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* limited contexts where the code knows that case #1 will never apply.)
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*
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* * Separately allocated minimal tuple: t_data points MINIMAL_TUPLE_OFFSET
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* bytes before the start of a MinimalTuple. As with the previous case,
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* this can't be told apart from case #1 by inspection; code setting up
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* or destroying this representation has to know what it's doing.
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*
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* t_len should always be valid, except in the pointer-to-nothing case.
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* t_self and t_tableOid should be valid if the HeapTupleData points to
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* a disk buffer, or if it represents a copy of a tuple on disk. They
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* should be explicitly set invalid in manufactured tuples.
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*/
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typedef struct HeapTupleData
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{
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uint32 t_len; /* length of *t_data */
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ItemPointerData t_self; /* SelfItemPointer */
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Oid t_tableOid; /* table the tuple came from */
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#define FIELDNO_HEAPTUPLEDATA_DATA 3
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HeapTupleHeader t_data; /* -> tuple header and data */
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} HeapTupleData;
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typedef HeapTupleData *HeapTuple;
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#define HEAPTUPLESIZE MAXALIGN(sizeof(HeapTupleData))
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/*
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* Accessor macros to be used with HeapTuple pointers.
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*/
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#define HeapTupleIsValid(tuple) PointerIsValid(tuple)
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/* HeapTupleHeader functions implemented in utils/time/combocid.c */
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extern CommandId HeapTupleHeaderGetCmin(HeapTupleHeader tup);
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extern CommandId HeapTupleHeaderGetCmax(HeapTupleHeader tup);
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extern void HeapTupleHeaderAdjustCmax(HeapTupleHeader tup,
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CommandId *cmax, bool *iscombo);
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/* Prototype for HeapTupleHeader accessors in heapam.c */
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extern TransactionId HeapTupleGetUpdateXid(HeapTupleHeader tuple);
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#endif /* HTUP_H */
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