diff options
Diffstat (limited to 'src/include/postgres.h')
| -rw-r--r-- | src/include/postgres.h | 84 |
1 files changed, 62 insertions, 22 deletions
diff --git a/src/include/postgres.h b/src/include/postgres.h index 30e1dee1870..cb9d196c519 100644 --- a/src/include/postgres.h +++ b/src/include/postgres.h @@ -54,23 +54,53 @@ */ /* - * struct varatt_external is a "TOAST pointer", that is, the information - * needed to fetch a stored-out-of-line Datum. The data is compressed - * if and only if va_extsize < va_rawsize - VARHDRSZ. This struct must not - * contain any padding, because we sometimes compare pointers using memcmp. + * struct varatt_external is a "TOAST pointer", that is, the information needed + * to fetch a Datum stored in an out-of-line on-disk Datum. The data is + * compressed if and only if va_extsize < va_rawsize - VARHDRSZ. This struct + * must not contain any padding, because we sometimes compare pointers using + * memcmp. * * Note that this information is stored unaligned within actual tuples, so * you need to memcpy from the tuple into a local struct variable before * you can look at these fields! (The reason we use memcmp is to avoid * having to do that just to detect equality of two TOAST pointers...) */ -struct varatt_external +typedef struct varatt_external { int32 va_rawsize; /* Original data size (includes header) */ int32 va_extsize; /* External saved size (doesn't) */ Oid va_valueid; /* Unique ID of value within TOAST table */ Oid va_toastrelid; /* RelID of TOAST table containing it */ -}; +} varatt_external; + +/* + * Out-of-line Datum thats stored in memory in contrast to varatt_external + * pointers which points to data in an external toast relation. + * + * Note that just as varatt_external's this is stored unaligned within the + * tuple. + */ +typedef struct varatt_indirect +{ + struct varlena *pointer; /* Pointer to in-memory varlena */ +} varatt_indirect; + + +/* + * Type of external toast datum stored. The peculiar value for VARTAG_ONDISK + * comes from the requirement for on-disk compatibility with the older + * definitions of varattrib_1b_e where v_tag was named va_len_1be... + */ +typedef enum vartag_external +{ + VARTAG_INDIRECT = 1, + VARTAG_ONDISK = 18 +} vartag_external; + +#define VARTAG_SIZE(tag) \ + ((tag) == VARTAG_INDIRECT ? sizeof(varatt_indirect) : \ + (tag) == VARTAG_ONDISK ? sizeof(varatt_external) : \ + TrapMacro(true, "unknown vartag")) /* * These structs describe the header of a varlena object that may have been @@ -102,11 +132,12 @@ typedef struct char va_data[1]; /* Data begins here */ } varattrib_1b; +/* inline portion of a short varlena pointing to an external resource */ typedef struct { uint8 va_header; /* Always 0x80 or 0x01 */ - uint8 va_len_1be; /* Physical length of datum */ - char va_data[1]; /* Data (for now always a TOAST pointer) */ + uint8 va_tag; /* Type of datum */ + char va_data[1]; /* Data (of the type indicated by va_tag) */ } varattrib_1b_e; /* @@ -130,6 +161,9 @@ typedef struct * first byte. Also, it is not possible for a 1-byte length word to be zero; * this lets us disambiguate alignment padding bytes from the start of an * unaligned datum. (We now *require* pad bytes to be filled with zero!) + * + * In TOAST datums the tag field in varattrib_1b_e is used to discern whether + * its an indirection pointer or more commonly an on-disk tuple. */ /* @@ -161,8 +195,8 @@ typedef struct (((varattrib_4b *) (PTR))->va_4byte.va_header & 0x3FFFFFFF) #define VARSIZE_1B(PTR) \ (((varattrib_1b *) (PTR))->va_header & 0x7F) -#define VARSIZE_1B_E(PTR) \ - (((varattrib_1b_e *) (PTR))->va_len_1be) +#define VARTAG_1B_E(PTR) \ + (((varattrib_1b_e *) (PTR))->va_tag) #define SET_VARSIZE_4B(PTR,len) \ (((varattrib_4b *) (PTR))->va_4byte.va_header = (len) & 0x3FFFFFFF) @@ -170,9 +204,9 @@ typedef struct (((varattrib_4b *) (PTR))->va_4byte.va_header = ((len) & 0x3FFFFFFF) | 0x40000000) #define SET_VARSIZE_1B(PTR,len) \ (((varattrib_1b *) (PTR))->va_header = (len) | 0x80) -#define SET_VARSIZE_1B_E(PTR,len) \ +#define SET_VARTAG_1B_E(PTR,tag) \ (((varattrib_1b_e *) (PTR))->va_header = 0x80, \ - ((varattrib_1b_e *) (PTR))->va_len_1be = (len)) + ((varattrib_1b_e *) (PTR))->va_tag = (tag)) #else /* !WORDS_BIGENDIAN */ #define VARATT_IS_4B(PTR) \ @@ -193,8 +227,8 @@ typedef struct ((((varattrib_4b *) (PTR))->va_4byte.va_header >> 2) & 0x3FFFFFFF) #define VARSIZE_1B(PTR) \ ((((varattrib_1b *) (PTR))->va_header >> 1) & 0x7F) -#define VARSIZE_1B_E(PTR) \ - (((varattrib_1b_e *) (PTR))->va_len_1be) +#define VARTAG_1B_E(PTR) \ + (((varattrib_1b_e *) (PTR))->va_tag) #define SET_VARSIZE_4B(PTR,len) \ (((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2)) @@ -202,12 +236,12 @@ typedef struct (((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2) | 0x02) #define SET_VARSIZE_1B(PTR,len) \ (((varattrib_1b *) (PTR))->va_header = (((uint8) (len)) << 1) | 0x01) -#define SET_VARSIZE_1B_E(PTR,len) \ +#define SET_VARTAG_1B_E(PTR,tag) \ (((varattrib_1b_e *) (PTR))->va_header = 0x01, \ - ((varattrib_1b_e *) (PTR))->va_len_1be = (len)) + ((varattrib_1b_e *) (PTR))->va_tag = (tag)) #endif /* WORDS_BIGENDIAN */ -#define VARHDRSZ_SHORT 1 +#define VARHDRSZ_SHORT offsetof(varattrib_1b, va_data) #define VARATT_SHORT_MAX 0x7F #define VARATT_CAN_MAKE_SHORT(PTR) \ (VARATT_IS_4B_U(PTR) && \ @@ -215,7 +249,7 @@ typedef struct #define VARATT_CONVERTED_SHORT_SIZE(PTR) \ (VARSIZE(PTR) - VARHDRSZ + VARHDRSZ_SHORT) -#define VARHDRSZ_EXTERNAL 2 +#define VARHDRSZ_EXTERNAL offsetof(varattrib_1b_e, va_data) #define VARDATA_4B(PTR) (((varattrib_4b *) (PTR))->va_4byte.va_data) #define VARDATA_4B_C(PTR) (((varattrib_4b *) (PTR))->va_compressed.va_data) @@ -249,26 +283,32 @@ typedef struct #define VARSIZE_SHORT(PTR) VARSIZE_1B(PTR) #define VARDATA_SHORT(PTR) VARDATA_1B(PTR) -#define VARSIZE_EXTERNAL(PTR) VARSIZE_1B_E(PTR) +#define VARTAG_EXTERNAL(PTR) VARTAG_1B_E(PTR) +#define VARSIZE_EXTERNAL(PTR) (VARHDRSZ_EXTERNAL + VARTAG_SIZE(VARTAG_EXTERNAL(PTR))) #define VARDATA_EXTERNAL(PTR) VARDATA_1B_E(PTR) #define VARATT_IS_COMPRESSED(PTR) VARATT_IS_4B_C(PTR) #define VARATT_IS_EXTERNAL(PTR) VARATT_IS_1B_E(PTR) +#define VARATT_IS_EXTERNAL_ONDISK(PTR) \ + (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_ONDISK) +#define VARATT_IS_EXTERNAL_INDIRECT(PTR) \ + (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_INDIRECT) #define VARATT_IS_SHORT(PTR) VARATT_IS_1B(PTR) #define VARATT_IS_EXTENDED(PTR) (!VARATT_IS_4B_U(PTR)) #define SET_VARSIZE(PTR, len) SET_VARSIZE_4B(PTR, len) #define SET_VARSIZE_SHORT(PTR, len) SET_VARSIZE_1B(PTR, len) #define SET_VARSIZE_COMPRESSED(PTR, len) SET_VARSIZE_4B_C(PTR, len) -#define SET_VARSIZE_EXTERNAL(PTR, len) SET_VARSIZE_1B_E(PTR, len) + +#define SET_VARTAG_EXTERNAL(PTR, tag) SET_VARTAG_1B_E(PTR, tag) #define VARSIZE_ANY(PTR) \ - (VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR) : \ + (VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR) : \ (VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR) : \ VARSIZE_4B(PTR))) #define VARSIZE_ANY_EXHDR(PTR) \ - (VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR)-VARHDRSZ_EXTERNAL : \ + (VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR)-VARHDRSZ_EXTERNAL : \ (VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR)-VARHDRSZ_SHORT : \ VARSIZE_4B(PTR)-VARHDRSZ)) |