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Recommend wrappers of PG_DETOAST_DATUM_PACKED().

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When commit 3e23b68dac introduced
single-byte varlena headers, its fmgr.h changes presented
PG_GETARG_TEXT_PP() and PG_GETARG_TEXT_P() as equals.  Its postgres.h
changes presented PG_DETOAST_DATUM_PACKED() and VARDATA_ANY() as the
exceptional case.  Now, instead, firmly recommend PG_GETARG_TEXT_PP()
over PG_GETARG_TEXT_P(); likewise for other ...PP() macros.  This shaves
cycles and invites consistency of style.
This commit is contained in:
Noah Misch
2017-03-12 19:35:33 -04:00
parent 944a026b4e
commit 9d7726c2ba
6 changed files with 74 additions and 57 deletions
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34
src/include/fmgr.h
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@@ -178,11 +178,12 @@ extern void fmgr_info_copy(FmgrInfo *dstinfo, FmgrInfo *srcinfo,
* The resulting datum can be accessed using VARSIZE_ANY() and VARDATA_ANY()
* (beware of multiple evaluations in those macros!)
*
* WARNING: It is only safe to use pg_detoast_datum_packed() and
* VARDATA_ANY() if you really don't care about the alignment. Either because
* you're working with something like text where the alignment doesn't matter
* or because you're not going to access its constituent parts and just use
* things like memcpy on it anyways.
* In consumers oblivious to data alignment, call PG_DETOAST_DATUM_PACKED(),
* VARDATA_ANY(), VARSIZE_ANY() and VARSIZE_ANY_EXHDR(). Elsewhere, call
* PG_DETOAST_DATUM(), VARDATA() and VARSIZE(). Directly fetching an int16,
* int32 or wider field in the struct representing the datum layout requires
* aligned data. memcpy() is alignment-oblivious, as are most operations on
* datatypes, such as text, whose layout struct contains only char fields.
*
* Note: it'd be nice if these could be macros, but I see no way to do that
* without evaluating the arguments multiple times, which is NOT acceptable.
@@ -243,13 +244,9 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena * datum);
/* and this if you can handle 1-byte-header datums: */
#define PG_GETARG_VARLENA_PP(n) PG_DETOAST_DATUM_PACKED(PG_GETARG_DATUM(n))
/* DatumGetFoo macros for varlena types will typically look like this: */
#define DatumGetByteaP(X) ((bytea *) PG_DETOAST_DATUM(X))
#define DatumGetByteaPP(X) ((bytea *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetTextP(X) ((text *) PG_DETOAST_DATUM(X))
#define DatumGetTextPP(X) ((text *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetBpCharP(X) ((BpChar *) PG_DETOAST_DATUM(X))
#define DatumGetBpCharPP(X) ((BpChar *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetVarCharP(X) ((VarChar *) PG_DETOAST_DATUM(X))
#define DatumGetVarCharPP(X) ((VarChar *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetHeapTupleHeader(X) ((HeapTupleHeader) PG_DETOAST_DATUM(X))
/* And we also offer variants that return an OK-to-write copy */
@@ -264,13 +261,9 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena * datum);
#define DatumGetBpCharPSlice(X,m,n) ((BpChar *) PG_DETOAST_DATUM_SLICE(X,m,n))
#define DatumGetVarCharPSlice(X,m,n) ((VarChar *) PG_DETOAST_DATUM_SLICE(X,m,n))
/* GETARG macros for varlena types will typically look like this: */
#define PG_GETARG_BYTEA_P(n) DatumGetByteaP(PG_GETARG_DATUM(n))
#define PG_GETARG_BYTEA_PP(n) DatumGetByteaPP(PG_GETARG_DATUM(n))
#define PG_GETARG_TEXT_P(n) DatumGetTextP(PG_GETARG_DATUM(n))
#define PG_GETARG_TEXT_PP(n) DatumGetTextPP(PG_GETARG_DATUM(n))
#define PG_GETARG_BPCHAR_P(n) DatumGetBpCharP(PG_GETARG_DATUM(n))
#define PG_GETARG_BPCHAR_PP(n) DatumGetBpCharPP(PG_GETARG_DATUM(n))
#define PG_GETARG_VARCHAR_P(n) DatumGetVarCharP(PG_GETARG_DATUM(n))
#define PG_GETARG_VARCHAR_PP(n) DatumGetVarCharPP(PG_GETARG_DATUM(n))
#define PG_GETARG_HEAPTUPLEHEADER(n) DatumGetHeapTupleHeader(PG_GETARG_DATUM(n))
/* And we also offer variants that return an OK-to-write copy */
@@ -284,6 +277,21 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena * datum);
#define PG_GETARG_TEXT_P_SLICE(n,a,b) DatumGetTextPSlice(PG_GETARG_DATUM(n),a,b)
#define PG_GETARG_BPCHAR_P_SLICE(n,a,b) DatumGetBpCharPSlice(PG_GETARG_DATUM(n),a,b)
#define PG_GETARG_VARCHAR_P_SLICE(n,a,b) DatumGetVarCharPSlice(PG_GETARG_DATUM(n),a,b)
/*
* Obsolescent variants that guarantee INT alignment for the return value.
* Few operations on these particular types need alignment, mainly operations
* that cast the VARDATA pointer to a type like int16[]. Most code should use
* the ...PP(X) counterpart. Nonetheless, these appear frequently in code
* predating the PostgreSQL 8.3 introduction of the ...PP(X) variants.
*/
#define DatumGetByteaP(X) ((bytea *) PG_DETOAST_DATUM(X))
#define DatumGetTextP(X) ((text *) PG_DETOAST_DATUM(X))
#define DatumGetBpCharP(X) ((BpChar *) PG_DETOAST_DATUM(X))
#define DatumGetVarCharP(X) ((VarChar *) PG_DETOAST_DATUM(X))
#define PG_GETARG_BYTEA_P(n) DatumGetByteaP(PG_GETARG_DATUM(n))
#define PG_GETARG_TEXT_P(n) DatumGetTextP(PG_GETARG_DATUM(n))
#define PG_GETARG_BPCHAR_P(n) DatumGetBpCharP(PG_GETARG_DATUM(n))
#define PG_GETARG_VARCHAR_P(n) DatumGetVarCharP(PG_GETARG_DATUM(n))
/* To return a NULL do this: */
#define PG_RETURN_NULL() \