diff options
| author | Bruce Momjian | 2007-05-15 17:39:54 +0000 |
|---|---|---|
| committer | Bruce Momjian | 2007-05-15 17:39:54 +0000 |
| commit | 2203c410dbf64f4ebe4a88fd57510d5d0981cc4d (patch) | |
| tree | 7267a06dd3b4bce736c5ec55cddb16b0c8db5be8 /src/include/postgres.h | |
| parent | 577843a120b01d797b9a5cb5a40801ee24abfe31 (diff) | |
Update comments for PG_DETOAST_PACKED and VARDATA_ANY on a structures
that require alignment.
Add a paragraph to the "User-Defined Types" chapter on using these
macros since it seems like they're a hit.
Gregory Stark
Diffstat (limited to 'src/include/postgres.h')
| -rw-r--r-- | src/include/postgres.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/include/postgres.h b/src/include/postgres.h index d7d1403654..030738ced4 100644 --- a/src/include/postgres.h +++ b/src/include/postgres.h @@ -235,6 +235,12 @@ typedef struct * use VARSIZE_ANY/VARSIZE_ANY_EXHDR/VARDATA_ANY. The other macros here * should usually be used only by tuple assembly/disassembly code and * code that specifically wants to work with still-toasted Datums. + * + * WARNING: It is only safe to use VARDATA_ANY() -- typically with + * PG_DETOAST_DATUM_UNPACKED() -- 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. */ #define VARDATA(PTR) VARDATA_4B(PTR) #define VARSIZE(PTR) VARSIZE_4B(PTR) @@ -265,6 +271,7 @@ typedef struct VARSIZE_4B(PTR)-4)) /* caution: this will not work on an external or compressed-in-line Datum */ +/* caution: this will return a possibly unaligned pointer */ #define VARDATA_ANY(PTR) \ (VARATT_IS_1B(PTR) ? VARDATA_1B(PTR) : VARDATA_4B(PTR)) |