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Add an extra header byte to TOAST-pointer datums to represent their size

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explicitly.  This means a TOAST pointer takes 18 bytes instead of 17 --- still
smaller than in 8.2 --- which seems a good tradeoff to ensure we won't have
painted ourselves into a corner if we want to support multiple types of TOAST
pointer later on.  Per discussion with Greg Stark.
This commit is contained in:
Tom Lane
2007-09-30 19:54:58 +00:00
parent 3ff0018c2e
commit 27b8922221
4 changed files with 58 additions and 37 deletions
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36
src/include/postgres.h
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@ -10,7 +10,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1995, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/postgres.h,v 1.83 2007/09/27 21:01:59 tgl Exp $
* $PostgreSQL: pgsql/src/include/postgres.h,v 1.84 2007/09/30 19:54:58 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -100,12 +100,20 @@ typedef union
typedef struct
{
uint8 va_header;
char va_data[1]; /* Data or TOAST pointer */
char va_data[1]; /* Data begins here */
} varattrib_1b;
typedef struct
{
uint8 va_header;
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) */
} varattrib_1b_e;
typedef struct
{
uint8 va_header; /* Always 0x80 or 0x01 */
uint8 va_len_1be; /* Physical length of datum */
char va_data[sizeof(struct varatt_external)];
} varattrib_pointer;
@ -161,9 +169,8 @@ typedef struct
(((varattrib_4b *) (PTR))->va_4byte.va_header & 0x3FFFFFFF)
#define VARSIZE_1B(PTR) \
(((varattrib_1b *) (PTR))->va_header & 0x7F)
/* Currently there is only one size of toast pointer, but someday maybe not */
#define VARSIZE_1B_E(PTR) \
(sizeof(varattrib_pointer))
(((varattrib_1b_e *) (PTR))->va_len_1be)
#define SET_VARSIZE_4B(PTR,len) \
(((varattrib_4b *) (PTR))->va_4byte.va_header = (len) & 0x3FFFFFFF)
@ -171,8 +178,9 @@ 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) \
(((varattrib_1b *) (PTR))->va_header = 0x80)
#define SET_VARSIZE_1B_E(PTR,len) \
(((varattrib_1b_e *) (PTR))->va_header = 0x80, \
((varattrib_1b_e *) (PTR))->va_len_1be = (len))
#else /* !WORDS_BIGENDIAN */
@ -194,9 +202,8 @@ typedef struct
((((varattrib_4b *) (PTR))->va_4byte.va_header >> 2) & 0x3FFFFFFF)
#define VARSIZE_1B(PTR) \
((((varattrib_1b *) (PTR))->va_header >> 1) & 0x7F)
/* Currently there is only one size of toast pointer, but someday maybe not */
#define VARSIZE_1B_E(PTR) \
(sizeof(varattrib_pointer))
(((varattrib_1b_e *) (PTR))->va_len_1be)
#define SET_VARSIZE_4B(PTR,len) \
(((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2))
@ -204,8 +211,9 @@ 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) \
(((varattrib_1b *) (PTR))->va_header = 0x01)
#define SET_VARSIZE_1B_E(PTR,len) \
(((varattrib_1b_e *) (PTR))->va_header = 0x01, \
((varattrib_1b_e *) (PTR))->va_len_1be = (len))
#endif /* WORDS_BIGENDIAN */
@ -220,6 +228,7 @@ typedef struct
#define VARDATA_4B(PTR) (((varattrib_4b *) (PTR))->va_4byte.va_data)
#define VARDATA_4B_C(PTR) (((varattrib_4b *) (PTR))->va_compressed.va_data)
#define VARDATA_1B(PTR) (((varattrib_1b *) (PTR))->va_data)
#define VARDATA_1B_E(PTR) (((varattrib_1b_e *) (PTR))->va_data)
#define VARRAWSIZE_4B_C(PTR) \
(((varattrib_4b *) (PTR))->va_compressed.va_rawsize)
@ -249,6 +258,7 @@ typedef struct
#define VARDATA_SHORT(PTR) VARDATA_1B(PTR)
#define VARSIZE_EXTERNAL(PTR) VARSIZE_1B_E(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)
@ -258,7 +268,7 @@ typedef struct
#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) SET_VARSIZE_1B_E(PTR)
#define SET_VARSIZE_EXTERNAL(PTR, len) SET_VARSIZE_1B_E(PTR, len)
#define VARSIZE_ANY(PTR) \
(VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR) : \
@ -266,7 +276,7 @@ typedef struct
VARSIZE_4B(PTR)))
#define VARSIZE_ANY_EXHDR(PTR) \
(VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR)-1 : \
(VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR)-2 : \
(VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR)-1 : \
VARSIZE_4B(PTR)-4))