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Commit9d7726c

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Recommend wrappers of PG_DETOAST_DATUM_PACKED().
When commit3e23b68 introducedsingle-byte varlena headers, its fmgr.h changes presentedPG_GETARG_TEXT_PP() and PG_GETARG_TEXT_P() as equals. Its postgres.hchanges presented PG_DETOAST_DATUM_PACKED() and VARDATA_ANY() as theexceptional case. Now, instead, firmly recommend PG_GETARG_TEXT_PP()over PG_GETARG_TEXT_P(); likewise for other ...PP() macros. This shavescycles and invites consistency of style.
1 parent944a026 commit9d7726c

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6 files changed

+76
-59
lines changed

6 files changed

+76
-59
lines changed

‎doc/src/sgml/xfunc.sgml

Lines changed: 19 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -2388,18 +2388,23 @@ PG_FUNCTION_INFO_V1(copytext);
23882388
Datum
23892389
copytext(PG_FUNCTION_ARGS)
23902390
{
2391-
text *t = PG_GETARG_TEXT_P(0);
2391+
text *t = PG_GETARG_TEXT_PP(0);
2392+
23922393
/*
2393-
* VARSIZE is the total size of the struct in bytes.
2394+
* VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the
2395+
* VARHDRSZ or VARHDRSZ_SHORT of its header. Construct the copy with a
2396+
* full-length header.
23942397
*/
2395-
text *new_t = (text *) palloc(VARSIZE(t));
2396-
SET_VARSIZE(new_t, VARSIZE(t));
2398+
text *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);
2399+
SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);
2400+
23972401
/*
2398-
* VARDATA is a pointer to the data region of the struct.
2402+
* VARDATA is a pointer to the data region of the new struct. The source
2403+
* could be a short datum, so retrieve its data through VARDATA_ANY.
23992404
*/
24002405
memcpy((void *) VARDATA(new_t), /* destination */
2401-
(void *)VARDATA(t), /* source */
2402-
VARSIZE(t) - VARHDRSZ); /* how many bytes */
2406+
(void *)VARDATA_ANY(t), /* source */
2407+
VARSIZE_ANY_EXHDR(t)); /* how many bytes */
24032408
PG_RETURN_TEXT_P(new_t);
24042409
}
24052410

@@ -2408,15 +2413,16 @@ PG_FUNCTION_INFO_V1(concat_text);
24082413
Datum
24092414
concat_text(PG_FUNCTION_ARGS)
24102415
{
2411-
text *arg1 = PG_GETARG_TEXT_P(0);
2412-
text *arg2 = PG_GETARG_TEXT_P(1);
2413-
int32 new_text_size = VARSIZE(arg1) + VARSIZE(arg2) - VARHDRSZ;
2416+
text *arg1 = PG_GETARG_TEXT_PP(0);
2417+
text *arg2 = PG_GETARG_TEXT_PP(1);
2418+
int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);
2419+
int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);
2420+
int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;
24142421
text *new_text = (text *) palloc(new_text_size);
24152422

24162423
SET_VARSIZE(new_text, new_text_size);
2417-
memcpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1) - VARHDRSZ);
2418-
memcpy(VARDATA(new_text) + (VARSIZE(arg1) - VARHDRSZ),
2419-
VARDATA(arg2), VARSIZE(arg2) - VARHDRSZ);
2424+
memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);
2425+
memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);
24202426
PG_RETURN_TEXT_P(new_text);
24212427
}
24222428
]]>

‎src/include/c.h

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -429,10 +429,11 @@ typedef struct
429429
* may be compressed or moved out-of-line. However datatype-specific routines
430430
* are mostly content to deal with de-TOASTed values only, and of course
431431
* client-side routines should never see a TOASTed value. But even in a
432-
* de-TOASTed value, beware of touching vl_len_ directly, as its representation
433-
* is no longer convenient. It's recommended that code always use the VARDATA,
434-
* VARSIZE, and SET_VARSIZE macros instead of relying on direct mentions of
435-
* the struct fields. See postgres.h for details of the TOASTed form.
432+
* de-TOASTed value, beware of touching vl_len_ directly, as its
433+
* representation is no longer convenient. It's recommended that code always
434+
* use macros VARDATA_ANY, VARSIZE_ANY, VARSIZE_ANY_EXHDR, VARDATA, VARSIZE,
435+
* and SET_VARSIZE instead of relying on direct mentions of the struct fields.
436+
* See postgres.h for details of the TOASTed form.
436437
* ----------------
437438
*/
438439
structvarlena

‎src/include/fmgr.h

Lines changed: 21 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -178,11 +178,12 @@ extern void fmgr_info_copy(FmgrInfo *dstinfo, FmgrInfo *srcinfo,
178178
* The resulting datum can be accessed using VARSIZE_ANY() and VARDATA_ANY()
179179
* (beware of multiple evaluations in those macros!)
180180
*
181-
* WARNING: It is only safe to use pg_detoast_datum_packed() and
182-
* VARDATA_ANY() if you really don't care about the alignment. Either because
183-
* you're working with something like text where the alignment doesn't matter
184-
* or because you're not going to access its constituent parts and just use
185-
* things like memcpy on it anyways.
181+
* In consumers oblivious to data alignment, call PG_DETOAST_DATUM_PACKED(),
182+
* VARDATA_ANY(), VARSIZE_ANY() and VARSIZE_ANY_EXHDR(). Elsewhere, call
183+
* PG_DETOAST_DATUM(), VARDATA() and VARSIZE(). Directly fetching an int16,
184+
* int32 or wider field in the struct representing the datum layout requires
185+
* aligned data. memcpy() is alignment-oblivious, as are most operations on
186+
* datatypes, such as text, whose layout struct contains only char fields.
186187
*
187188
* Note: it'd be nice if these could be macros, but I see no way to do that
188189
* without evaluating the arguments multiple times, which is NOT acceptable.
@@ -243,13 +244,9 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena * datum);
243244
/* and this if you can handle 1-byte-header datums: */
244245
#definePG_GETARG_VARLENA_PP(n) PG_DETOAST_DATUM_PACKED(PG_GETARG_DATUM(n))
245246
/* DatumGetFoo macros for varlena types will typically look like this: */
246-
#defineDatumGetByteaP(X)((bytea *) PG_DETOAST_DATUM(X))
247247
#defineDatumGetByteaPP(X)((bytea *) PG_DETOAST_DATUM_PACKED(X))
248-
#defineDatumGetTextP(X)((text *) PG_DETOAST_DATUM(X))
249248
#defineDatumGetTextPP(X)((text *) PG_DETOAST_DATUM_PACKED(X))
250-
#defineDatumGetBpCharP(X)((BpChar *) PG_DETOAST_DATUM(X))
251249
#defineDatumGetBpCharPP(X)((BpChar *) PG_DETOAST_DATUM_PACKED(X))
252-
#defineDatumGetVarCharP(X)((VarChar *) PG_DETOAST_DATUM(X))
253250
#defineDatumGetVarCharPP(X)((VarChar *) PG_DETOAST_DATUM_PACKED(X))
254251
#defineDatumGetHeapTupleHeader(X)((HeapTupleHeader) PG_DETOAST_DATUM(X))
255252
/* 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);
264261
#defineDatumGetBpCharPSlice(X,m,n) ((BpChar *) PG_DETOAST_DATUM_SLICE(X,m,n))
265262
#defineDatumGetVarCharPSlice(X,m,n) ((VarChar *) PG_DETOAST_DATUM_SLICE(X,m,n))
266263
/* GETARG macros for varlena types will typically look like this: */
267-
#definePG_GETARG_BYTEA_P(n)DatumGetByteaP(PG_GETARG_DATUM(n))
268264
#definePG_GETARG_BYTEA_PP(n)DatumGetByteaPP(PG_GETARG_DATUM(n))
269-
#definePG_GETARG_TEXT_P(n)DatumGetTextP(PG_GETARG_DATUM(n))
270265
#definePG_GETARG_TEXT_PP(n)DatumGetTextPP(PG_GETARG_DATUM(n))
271-
#definePG_GETARG_BPCHAR_P(n)DatumGetBpCharP(PG_GETARG_DATUM(n))
272266
#definePG_GETARG_BPCHAR_PP(n)DatumGetBpCharPP(PG_GETARG_DATUM(n))
273-
#definePG_GETARG_VARCHAR_P(n)DatumGetVarCharP(PG_GETARG_DATUM(n))
274267
#definePG_GETARG_VARCHAR_PP(n)DatumGetVarCharPP(PG_GETARG_DATUM(n))
275268
#definePG_GETARG_HEAPTUPLEHEADER(n)DatumGetHeapTupleHeader(PG_GETARG_DATUM(n))
276269
/* 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);
284277
#definePG_GETARG_TEXT_P_SLICE(n,a,b) DatumGetTextPSlice(PG_GETARG_DATUM(n),a,b)
285278
#definePG_GETARG_BPCHAR_P_SLICE(n,a,b) DatumGetBpCharPSlice(PG_GETARG_DATUM(n),a,b)
286279
#definePG_GETARG_VARCHAR_P_SLICE(n,a,b) DatumGetVarCharPSlice(PG_GETARG_DATUM(n),a,b)
280+
/*
281+
* Obsolescent variants that guarantee INT alignment for the return value.
282+
* Few operations on these particular types need alignment, mainly operations
283+
* that cast the VARDATA pointer to a type like int16[]. Most code should use
284+
* the ...PP(X) counterpart. Nonetheless, these appear frequently in code
285+
* predating the PostgreSQL 8.3 introduction of the ...PP(X) variants.
286+
*/
287+
#defineDatumGetByteaP(X)((bytea *) PG_DETOAST_DATUM(X))
288+
#defineDatumGetTextP(X)((text *) PG_DETOAST_DATUM(X))
289+
#defineDatumGetBpCharP(X)((BpChar *) PG_DETOAST_DATUM(X))
290+
#defineDatumGetVarCharP(X)((VarChar *) PG_DETOAST_DATUM(X))
291+
#definePG_GETARG_BYTEA_P(n)DatumGetByteaP(PG_GETARG_DATUM(n))
292+
#definePG_GETARG_TEXT_P(n)DatumGetTextP(PG_GETARG_DATUM(n))
293+
#definePG_GETARG_BPCHAR_P(n)DatumGetBpCharP(PG_GETARG_DATUM(n))
294+
#definePG_GETARG_VARCHAR_P(n)DatumGetVarCharP(PG_GETARG_DATUM(n))
287295

288296
/* To return a NULL do this: */
289297
#definePG_RETURN_NULL() \

‎src/include/postgres.h

Lines changed: 12 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -287,20 +287,18 @@ typedef struct
287287
/* Externally visible macros */
288288

289289
/*
290-
* VARDATA, VARSIZE, and SET_VARSIZE are the recommended API for most code
291-
* for varlena datatypes. Note that they only work on untoasted,
292-
* 4-byte-header Datums!
293-
*
294-
* Code that wants to use 1-byte-header values without detoasting should
295-
* use VARSIZE_ANY/VARSIZE_ANY_EXHDR/VARDATA_ANY. The other macros here
296-
* should usually be used only by tuple assembly/disassembly code and
297-
* code that specifically wants to work with still-toasted Datums.
298-
*
299-
* WARNING: It is only safe to use VARDATA_ANY() -- typically with
300-
* PG_DETOAST_DATUM_PACKED() -- if you really don't care about the alignment.
301-
* Either because you're working with something like text where the alignment
302-
* doesn't matter or because you're not going to access its constituent parts
303-
* and just use things like memcpy on it anyways.
290+
* In consumers oblivious to data alignment, call PG_DETOAST_DATUM_PACKED(),
291+
* VARDATA_ANY(), VARSIZE_ANY() and VARSIZE_ANY_EXHDR(). Elsewhere, call
292+
* PG_DETOAST_DATUM(), VARDATA() and VARSIZE(). Directly fetching an int16,
293+
* int32 or wider field in the struct representing the datum layout requires
294+
* aligned data. memcpy() is alignment-oblivious, as are most operations on
295+
* datatypes, such as text, whose layout struct contains only char fields.
296+
*
297+
* Code assembling a new datum should call VARDATA() and SET_VARSIZE().
298+
* (Datums begin life untoasted.)
299+
*
300+
* Other macros here should usually be used only by tuple assembly/disassembly
301+
* code and code that specifically wants to work with still-toasted Datums.
304302
*/
305303
#defineVARDATA(PTR)VARDATA_4B(PTR)
306304
#defineVARSIZE(PTR)VARSIZE_4B(PTR)

‎src/include/utils/inet.h

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -104,12 +104,13 @@ typedef struct macaddr
104104
/*
105105
* fmgr interface macros
106106
*/
107-
#defineDatumGetInetP(X)((inet *) PG_DETOAST_DATUM(X))
108107
#defineDatumGetInetPP(X)((inet *) PG_DETOAST_DATUM_PACKED(X))
109108
#defineInetPGetDatum(X)PointerGetDatum(X)
110-
#definePG_GETARG_INET_P(n) DatumGetInetP(PG_GETARG_DATUM(n))
111109
#definePG_GETARG_INET_PP(n) DatumGetInetPP(PG_GETARG_DATUM(n))
112110
#definePG_RETURN_INET_P(x) return InetPGetDatum(x)
111+
/* obsolescent variants */
112+
#defineDatumGetInetP(X)((inet *) PG_DETOAST_DATUM(X))
113+
#definePG_GETARG_INET_P(n) DatumGetInetP(PG_GETARG_DATUM(n))
113114
/* macaddr is a fixed-length pass-by-reference datatype */
114115
#defineDatumGetMacaddrP(X) ((macaddr *) DatumGetPointer(X))
115116
#defineMacaddrPGetDatum(X) PointerGetDatum(X)

‎src/tutorial/funcs_new.c

Lines changed: 16 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -66,21 +66,24 @@ PG_FUNCTION_INFO_V1(copytext);
6666
Datum
6767
copytext(PG_FUNCTION_ARGS)
6868
{
69-
text*t=PG_GETARG_TEXT_P(0);
69+
text*t=PG_GETARG_TEXT_PP(0);
7070

7171
/*
72-
* VARSIZE is the total size of the struct in bytes.
72+
* VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the
73+
* VARHDRSZ or VARHDRSZ_SHORT of its header. Construct the copy with a
74+
* full-length header.
7375
*/
74-
text*new_t= (text*)palloc(VARSIZE(t));
76+
text*new_t= (text*)palloc(VARSIZE_ANY_EXHDR(t)+VARHDRSZ);
7577

76-
SET_VARSIZE(new_t,VARSIZE(t));
78+
SET_VARSIZE(new_t,VARSIZE_ANY_EXHDR(t)+VARHDRSZ);
7779

7880
/*
79-
* VARDATA is a pointer to the data region of the struct.
81+
* VARDATA is a pointer to the data region of the new struct. The source
82+
* could be a short datum, so retrieve its data through VARDATA_ANY.
8083
*/
8184
memcpy((void*)VARDATA(new_t),/* destination */
82-
(void*)VARDATA(t),/* source */
83-
VARSIZE(t)-VARHDRSZ);/* how many bytes */
85+
(void*)VARDATA_ANY(t),/* source */
86+
VARSIZE_ANY_EXHDR(t));/* how many bytes */
8487
PG_RETURN_TEXT_P(new_t);
8588
}
8689

@@ -89,16 +92,16 @@ PG_FUNCTION_INFO_V1(concat_text);
8992
Datum
9093
concat_text(PG_FUNCTION_ARGS)
9194
{
92-
text*arg1=PG_GETARG_TEXT_P(0);
93-
text*arg2=PG_GETARG_TEXT_P(1);
94-
int32arg1_size=VARSIZE(arg1)-VARHDRSZ;
95-
int32arg2_size=VARSIZE(arg2)-VARHDRSZ;
95+
text*arg1=PG_GETARG_TEXT_PP(0);
96+
text*arg2=PG_GETARG_TEXT_PP(1);
97+
int32arg1_size=VARSIZE_ANY_EXHDR(arg1);
98+
int32arg2_size=VARSIZE_ANY_EXHDR(arg2);
9699
int32new_text_size=arg1_size+arg2_size+VARHDRSZ;
97100
text*new_text= (text*)palloc(new_text_size);
98101

99102
SET_VARSIZE(new_text,new_text_size);
100-
memcpy(VARDATA(new_text),VARDATA(arg1),arg1_size);
101-
memcpy(VARDATA(new_text)+arg1_size,VARDATA(arg2),arg2_size);
103+
memcpy(VARDATA(new_text),VARDATA_ANY(arg1),arg1_size);
104+
memcpy(VARDATA(new_text)+arg1_size,VARDATA_ANY(arg2),arg2_size);
102105
PG_RETURN_TEXT_P(new_text);
103106
}
104107

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