diff options
Diffstat (limited to 'src/include/executor')
| -rw-r--r-- | src/include/executor/tuptable.h | 32 |
1 files changed, 22 insertions, 10 deletions
diff --git a/src/include/executor/tuptable.h b/src/include/executor/tuptable.h index 1cd624b0859..d712106c524 100644 --- a/src/include/executor/tuptable.h +++ b/src/include/executor/tuptable.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/executor/tuptable.h,v 1.40 2009/01/01 17:23:59 momjian Exp $ + * $PostgreSQL: pgsql/src/include/executor/tuptable.h,v 1.41 2009/03/30 04:08:43 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -49,6 +49,14 @@ * 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 @@ -91,12 +99,12 @@ * * 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_shouldFree is true). In this case - * tts_tuple points at tts_minhdr and the fields of that are set correctly + * 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. (tts_mintuple is therefore - * redundant, but for code simplicity we store it explicitly anyway.) This - * case otherwise behaves identically to the regular-physical-tuple case. + * MINIMAL_TUPLE_OFFSET bytes before tts_mintuple. This allows column + * extraction to treat the case identically to regular physical tuples. * * tts_slow/tts_off are saved state for slot_deform_tuple, and should not * be touched by any other code. @@ -106,20 +114,24 @@ typedef struct TupleTableSlot { NodeTag type; /* vestigial ... allows IsA tests */ bool tts_isempty; /* true = slot is empty */ - bool tts_shouldFree; /* should pfree tuple? */ + bool tts_shouldFree; /* should pfree tts_tuple? */ + bool tts_shouldFreeMin; /* should pfree tts_mintuple? */ bool tts_slow; /* saved state for slot_deform_tuple */ - HeapTuple tts_tuple; /* physical tuple, or NULL if none */ + HeapTuple tts_tuple; /* physical tuple, or NULL if virtual */ TupleDesc tts_tupleDescriptor; /* slot's tuple descriptor */ MemoryContext tts_mcxt; /* slot itself is in this context */ Buffer tts_buffer; /* tuple's buffer, or InvalidBuffer */ int tts_nvalid; /* # of valid values in tts_values */ Datum *tts_values; /* current per-attribute values */ bool *tts_isnull; /* current per-attribute isnull flags */ - MinimalTuple tts_mintuple; /* set if it's a minimal tuple, else NULL */ - HeapTupleData tts_minhdr; /* workspace if it's a minimal tuple */ + MinimalTuple tts_mintuple; /* minimal tuple, or NULL if none */ + HeapTupleData tts_minhdr; /* workspace for minimal-tuple-only case */ long tts_off; /* saved state for slot_deform_tuple */ } TupleTableSlot; +#define TTS_HAS_PHYSICAL_TUPLE(slot) \ + ((slot)->tts_tuple != NULL && (slot)->tts_tuple != &((slot)->tts_minhdr)) + /* * Tuple table data structure: an array of TupleTableSlots. */ |