diff options
Diffstat (limited to 'src/include/access/spgist_private.h')
| -rw-r--r-- | src/include/access/spgist_private.h | 40 |
1 files changed, 23 insertions, 17 deletions
diff --git a/src/include/access/spgist_private.h b/src/include/access/spgist_private.h index a81bab24ea4..b6f95421d8f 100644 --- a/src/include/access/spgist_private.h +++ b/src/include/access/spgist_private.h @@ -266,6 +266,14 @@ typedef struct SpGistCache * header/optional prefix/array of nodes, which are SpGistNodeTuples * * size and prefixSize must be multiples of MAXALIGN + * + * If the prefix datum is of a pass-by-value type, it is stored in its + * Datum representation, that is its on-disk representation is of length + * sizeof(Datum). This is a fairly unfortunate choice, because in no other + * place does Postgres use Datum as an on-disk representation; it creates + * an unnecessary incompatibility between 32-bit and 64-bit builds. But the + * compatibility loss is mostly theoretical since MAXIMUM_ALIGNOF typically + * differs between such builds, too. Anyway we're stuck with it now. */ typedef struct SpGistInnerTupleData { @@ -307,8 +315,7 @@ typedef SpGistInnerTupleData *SpGistInnerTuple; * Node tuples use the same header as ordinary Postgres IndexTuples, but * we do not use a null bitmap, because we know there is only one column * so the INDEX_NULL_MASK bit suffices. Also, pass-by-value datums are - * stored as a full Datum, the same convention as for inner tuple prefixes - * and leaf tuple datums. + * stored in Datum form, the same convention as for inner tuple prefixes. */ typedef IndexTupleData SpGistNodeTupleData; @@ -322,12 +329,15 @@ typedef SpGistNodeTupleData *SpGistNodeTuple; PointerGetDatum(SGNTDATAPTR(x))) /* - * SPGiST leaf tuple: carries a datum and a heap tuple TID + * SPGiST leaf tuple: carries a leaf datum and a heap tuple TID * - * In the simplest case, the datum is the same as the indexed value; but - * it could also be a suffix or some other sort of delta that permits + * In the simplest case, the leaf datum is the same as the indexed value; + * but it could also be a suffix or some other sort of delta that permits * reconstruction given knowledge of the prefix path traversed to get here. * + * If the leaf datum is NULL, it's not stored. This is not represented + * explicitly; we infer it from the tuple being stored on a nulls page. + * * The size field is wider than could possibly be needed for an on-disk leaf * tuple, but this allows us to form leaf tuples even when the datum is too * wide to be stored immediately, and it costs nothing because of alignment @@ -339,13 +349,8 @@ typedef SpGistNodeTupleData *SpGistNodeTuple; * * size must be a multiple of MAXALIGN; also, it must be at least SGDTSIZE * so that the tuple can be converted to REDIRECT status later. (This - * restriction only adds bytes for the null-datum case, otherwise alignment - * restrictions force it anyway.) - * - * In a leaf tuple for a NULL indexed value, there's no useful datum value; - * however, the SGDTSIZE limit ensures that's there's a Datum word there - * anyway, so SGLTDATUM can be applied safely as long as you don't do - * anything with the result. + * restriction only adds bytes for a NULL leaf datum stored on a 32-bit + * machine; otherwise alignment restrictions force it anyway.) */ typedef struct SpGistLeafTupleData { @@ -353,16 +358,16 @@ typedef struct SpGistLeafTupleData size:30; /* large enough for any palloc'able value */ OffsetNumber nextOffset; /* next tuple in chain, or InvalidOffsetNumber */ ItemPointerData heapPtr; /* TID of represented heap tuple */ - /* leaf datum follows */ + /* leaf datum follows on a MAXALIGN boundary */ } SpGistLeafTupleData; typedef SpGistLeafTupleData *SpGistLeafTuple; #define SGLTHDRSZ MAXALIGN(sizeof(SpGistLeafTupleData)) #define SGLTDATAPTR(x) (((char *) (x)) + SGLTHDRSZ) -#define SGLTDATUM(x, s) ((s)->attLeafType.attbyval ? \ - *(Datum *) SGLTDATAPTR(x) : \ - PointerGetDatum(SGLTDATAPTR(x))) +#define SGLTDATUM(x, s) fetch_att(SGLTDATAPTR(x), \ + (s)->attLeafType.attbyval, \ + (s)->attLeafType.attlen) /* * SPGiST dead tuple: declaration for examining non-live tuples @@ -455,7 +460,8 @@ extern void SpGistSetLastUsedPage(Relation index, Buffer buffer); extern void SpGistInitPage(Page page, uint16 f); extern void SpGistInitBuffer(Buffer b, uint16 f); extern void SpGistInitMetapage(Page page); -extern unsigned int SpGistGetTypeSize(SpGistTypeDesc *att, Datum datum); +extern unsigned int SpGistGetInnerTypeSize(SpGistTypeDesc *att, Datum datum); +extern unsigned int SpGistGetLeafTypeSize(SpGistTypeDesc *att, Datum datum); extern SpGistLeafTuple spgFormLeafTuple(SpGistState *state, ItemPointer heapPtr, Datum datum, bool isnull); |