diff options
Diffstat (limited to 'src/include/access/tuptoaster.h')
| -rw-r--r-- | src/include/access/tuptoaster.h | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/src/include/access/tuptoaster.h b/src/include/access/tuptoaster.h index 5adf4f28169..296d016c9fc 100644 --- a/src/include/access/tuptoaster.h +++ b/src/include/access/tuptoaster.h @@ -98,9 +98,34 @@ /* Size of an EXTERNAL datum that contains a standard TOAST pointer */ #define TOAST_POINTER_SIZE (VARHDRSZ_EXTERNAL + sizeof(struct varatt_external)) -/* Size of an indirect datum that contains an indirect TOAST pointer */ +/* Size of an indirect datum that contains a standard TOAST pointer */ #define INDIRECT_POINTER_SIZE (VARHDRSZ_EXTERNAL + sizeof(struct varatt_indirect)) +/* + * Testing whether an externally-stored value is compressed now requires + * comparing extsize (the actual length of the external data) to rawsize + * (the original uncompressed datum's size). The latter includes VARHDRSZ + * overhead, the former doesn't. We never use compression unless it actually + * saves space, so we expect either equality or less-than. + */ +#define VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) \ + ((toast_pointer).va_extsize < (toast_pointer).va_rawsize - VARHDRSZ) + +/* + * Macro to fetch the possibly-unaligned contents of an EXTERNAL datum + * into a local "struct varatt_external" toast pointer. This should be + * just a memcpy, but some versions of gcc seem to produce broken code + * that assumes the datum contents are aligned. Introducing an explicit + * intermediate "varattrib_1b_e *" variable seems to fix it. + */ +#define VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr) \ +do { \ + varattrib_1b_e *attre = (varattrib_1b_e *) (attr); \ + Assert(VARATT_IS_EXTERNAL(attre)); \ + Assert(VARSIZE_EXTERNAL(attre) == sizeof(toast_pointer) + VARHDRSZ_EXTERNAL); \ + memcpy(&(toast_pointer), VARDATA_EXTERNAL(attre), sizeof(toast_pointer)); \ +} while (0) + /* ---------- * toast_insert_or_update - * |