Add an extra header byte to TOAST-pointer datums to represent their size
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
parent
3ff0018c2e
commit
27b8922221
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@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.19 2007/09/21 21:25:42 tgl Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.20 2007/09/30 19:54:57 tgl Exp $ -->
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<chapter id="storage">
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@ -233,8 +233,8 @@ header, and the remaining bits give the total datum size (including length
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byte) in bytes. As a special case, if the remaining bits are all zero
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(which would be impossible for a self-inclusive length), the value is a
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pointer to out-of-line data stored in a separate TOAST table. (The size of
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a TOAST pointer is known a priori, so it doesn't need to be represented in
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the header.) Values with single-byte headers aren't aligned on any particular
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a TOAST pointer is given in the second byte of the datum.)
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Values with single-byte headers aren't aligned on any particular
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boundary, either. Lastly, when the highest-order or lowest-order bit is
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clear but the adjacent bit is set, the content of the datum has been
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compressed and must be decompressed before use. In this case the remaining
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@ -274,8 +274,8 @@ retrieval of the values. A pointer datum representing an out-of-line
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<acronym>TOAST</> table in which to look and the OID of the specific value
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(its <structfield>chunk_id</>). For convenience, pointer datums also store the
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logical datum size (original uncompressed data length) and actual stored size
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(different if compression was applied). Allowing for the varlena header byte,
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the total size of a <acronym>TOAST</> pointer datum is therefore 17 bytes
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(different if compression was applied). Allowing for the varlena header bytes,
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the total size of a <acronym>TOAST</> pointer datum is therefore 18 bytes
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regardless of the actual size of the represented value.
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</para>
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.75 2007/09/26 23:29:10 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.76 2007/09/30 19:54:58 tgl Exp $
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*
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*
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* INTERFACE ROUTINES
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@ -52,6 +52,21 @@
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#define VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) \
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((toast_pointer).va_extsize < (toast_pointer).va_rawsize - VARHDRSZ)
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/*
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* Macro to fetch the possibly-unaligned contents of an EXTERNAL datum
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* into a local "struct varatt_external" toast pointer. This should be
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* just a memcpy, but some versions of gcc seem to produce broken code
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* that assumes the datum contents are aligned. Introducing an explicit
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* intermediate "varattrib_1b_e *" variable seems to fix it.
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*/
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#define VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr) \
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do { \
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varattrib_1b_e *attre = (varattrib_1b_e *) (attr); \
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Assert(VARSIZE_ANY_EXHDR(attre) == sizeof(toast_pointer)); \
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memcpy(&(toast_pointer), VARDATA_EXTERNAL(attre), sizeof(toast_pointer)); \
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} while (0)
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static void toast_delete_datum(Relation rel, Datum value);
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static Datum toast_save_datum(Relation rel, Datum value,
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bool use_wal, bool use_fsm);
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@ -172,7 +187,7 @@ heap_tuple_untoast_attr_slice(struct varlena *attr,
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{
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struct varatt_external toast_pointer;
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memcpy(&toast_pointer, VARDATA_SHORT(attr), sizeof(toast_pointer));
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VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
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/* fast path for non-compressed external datums */
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if (!VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer))
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@ -249,7 +264,7 @@ toast_raw_datum_size(Datum value)
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/* va_rawsize is the size of the original datum -- including header */
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struct varatt_external toast_pointer;
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memcpy(&toast_pointer, VARDATA_SHORT(attr), sizeof(toast_pointer));
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VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
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result = toast_pointer.va_rawsize;
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}
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else if (VARATT_IS_COMPRESSED(attr))
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@ -294,7 +309,7 @@ toast_datum_size(Datum value)
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*/
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struct varatt_external toast_pointer;
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memcpy(&toast_pointer, VARDATA_SHORT(attr), sizeof(toast_pointer));
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VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
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result = toast_pointer.va_extsize;
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}
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else if (VARATT_IS_SHORT(attr))
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@ -470,9 +485,8 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
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VARATT_IS_EXTERNAL(old_value))
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{
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if (toast_isnull[i] || !VARATT_IS_EXTERNAL(new_value) ||
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memcmp(VARDATA_SHORT(old_value),
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VARDATA_SHORT(new_value),
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sizeof(struct varatt_external)) != 0)
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memcmp((char *) old_value, (char *) new_value,
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VARSIZE_EXTERNAL(old_value)) != 0)
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{
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/*
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* The old external stored value isn't needed any more
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@ -1071,7 +1085,7 @@ toast_save_datum(Relation rel, Datum value,
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Datum t_values[3];
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bool t_isnull[3];
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CommandId mycid = GetCurrentCommandId();
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struct varlena *result;
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varattrib_pointer *result;
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struct varatt_external toast_pointer;
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struct
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{
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@ -1192,9 +1206,9 @@ toast_save_datum(Relation rel, Datum value,
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/*
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* Create the TOAST pointer value that we'll return
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*/
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result = (struct varlena *) palloc(sizeof(varattrib_pointer));
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SET_VARSIZE_EXTERNAL(result);
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memcpy(VARDATA_SHORT(result), &toast_pointer, sizeof(toast_pointer));
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result = (varattrib_pointer *) palloc(sizeof(varattrib_pointer));
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SET_VARSIZE_EXTERNAL(result, sizeof(varattrib_pointer));
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memcpy(VARDATA_EXTERNAL(result), &toast_pointer, sizeof(toast_pointer));
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return PointerGetDatum(result);
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}
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@ -1221,8 +1235,7 @@ toast_delete_datum(Relation rel, Datum value)
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return;
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/* Must copy to access aligned fields */
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memcpy(&toast_pointer, VARDATA_SHORT(attr),
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sizeof(struct varatt_external));
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VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
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/*
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* Open the toast relation and its index
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@ -1289,8 +1302,7 @@ toast_fetch_datum(struct varlena *attr)
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int32 chunksize;
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/* Must copy to access aligned fields */
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memcpy(&toast_pointer, VARDATA_SHORT(attr),
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sizeof(struct varatt_external));
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VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
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ressize = toast_pointer.va_extsize;
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numchunks = ((ressize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
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@ -1452,8 +1464,7 @@ toast_fetch_datum_slice(struct varlena *attr, int32 sliceoffset, int32 length)
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Assert(VARATT_IS_EXTERNAL(attr));
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/* Must copy to access aligned fields */
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memcpy(&toast_pointer, VARDATA_SHORT(attr),
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sizeof(struct varatt_external));
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VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
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/*
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* It's nonsense to fetch slices of a compressed datum -- this isn't lo_*
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@ -37,7 +37,7 @@
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* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.429 2007/09/25 22:21:55 tgl Exp $
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* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.430 2007/09/30 19:54:58 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -53,6 +53,6 @@
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*/
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/* yyyymmddN */
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#define CATALOG_VERSION_NO 200709251
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#define CATALOG_VERSION_NO 200709301
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#endif
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@ -10,7 +10,7 @@
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* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
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* Portions Copyright (c) 1995, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/postgres.h,v 1.83 2007/09/27 21:01:59 tgl Exp $
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* $PostgreSQL: pgsql/src/include/postgres.h,v 1.84 2007/09/30 19:54:58 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -100,12 +100,20 @@ typedef union
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typedef struct
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{
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uint8 va_header;
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char va_data[1]; /* Data or TOAST pointer */
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char va_data[1]; /* Data begins here */
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} varattrib_1b;
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typedef struct
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{
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uint8 va_header;
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uint8 va_header; /* Always 0x80 or 0x01 */
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uint8 va_len_1be; /* Physical length of datum */
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char va_data[1]; /* Data (for now always a TOAST pointer) */
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} varattrib_1b_e;
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typedef struct
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{
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uint8 va_header; /* Always 0x80 or 0x01 */
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uint8 va_len_1be; /* Physical length of datum */
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char va_data[sizeof(struct varatt_external)];
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} varattrib_pointer;
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@ -161,9 +169,8 @@ typedef struct
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(((varattrib_4b *) (PTR))->va_4byte.va_header & 0x3FFFFFFF)
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#define VARSIZE_1B(PTR) \
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(((varattrib_1b *) (PTR))->va_header & 0x7F)
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/* Currently there is only one size of toast pointer, but someday maybe not */
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#define VARSIZE_1B_E(PTR) \
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(sizeof(varattrib_pointer))
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(((varattrib_1b_e *) (PTR))->va_len_1be)
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#define SET_VARSIZE_4B(PTR,len) \
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(((varattrib_4b *) (PTR))->va_4byte.va_header = (len) & 0x3FFFFFFF)
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@ -171,8 +178,9 @@ typedef struct
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(((varattrib_4b *) (PTR))->va_4byte.va_header = ((len) & 0x3FFFFFFF) | 0x40000000)
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#define SET_VARSIZE_1B(PTR,len) \
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(((varattrib_1b *) (PTR))->va_header = (len) | 0x80)
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#define SET_VARSIZE_1B_E(PTR) \
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(((varattrib_1b *) (PTR))->va_header = 0x80)
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#define SET_VARSIZE_1B_E(PTR,len) \
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(((varattrib_1b_e *) (PTR))->va_header = 0x80, \
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((varattrib_1b_e *) (PTR))->va_len_1be = (len))
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#else /* !WORDS_BIGENDIAN */
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@ -194,9 +202,8 @@ typedef struct
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((((varattrib_4b *) (PTR))->va_4byte.va_header >> 2) & 0x3FFFFFFF)
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#define VARSIZE_1B(PTR) \
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((((varattrib_1b *) (PTR))->va_header >> 1) & 0x7F)
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/* Currently there is only one size of toast pointer, but someday maybe not */
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#define VARSIZE_1B_E(PTR) \
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(sizeof(varattrib_pointer))
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(((varattrib_1b_e *) (PTR))->va_len_1be)
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#define SET_VARSIZE_4B(PTR,len) \
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(((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2))
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@ -204,8 +211,9 @@ typedef struct
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(((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2) | 0x02)
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#define SET_VARSIZE_1B(PTR,len) \
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(((varattrib_1b *) (PTR))->va_header = (((uint8) (len)) << 1) | 0x01)
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#define SET_VARSIZE_1B_E(PTR) \
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(((varattrib_1b *) (PTR))->va_header = 0x01)
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#define SET_VARSIZE_1B_E(PTR,len) \
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(((varattrib_1b_e *) (PTR))->va_header = 0x01, \
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((varattrib_1b_e *) (PTR))->va_len_1be = (len))
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#endif /* WORDS_BIGENDIAN */
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@ -220,6 +228,7 @@ typedef struct
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#define VARDATA_4B(PTR) (((varattrib_4b *) (PTR))->va_4byte.va_data)
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#define VARDATA_4B_C(PTR) (((varattrib_4b *) (PTR))->va_compressed.va_data)
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#define VARDATA_1B(PTR) (((varattrib_1b *) (PTR))->va_data)
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#define VARDATA_1B_E(PTR) (((varattrib_1b_e *) (PTR))->va_data)
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#define VARRAWSIZE_4B_C(PTR) \
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(((varattrib_4b *) (PTR))->va_compressed.va_rawsize)
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@ -249,6 +258,7 @@ typedef struct
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#define VARDATA_SHORT(PTR) VARDATA_1B(PTR)
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#define VARSIZE_EXTERNAL(PTR) VARSIZE_1B_E(PTR)
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#define VARDATA_EXTERNAL(PTR) VARDATA_1B_E(PTR)
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#define VARATT_IS_COMPRESSED(PTR) VARATT_IS_4B_C(PTR)
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#define VARATT_IS_EXTERNAL(PTR) VARATT_IS_1B_E(PTR)
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@ -258,7 +268,7 @@ typedef struct
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#define SET_VARSIZE(PTR, len) SET_VARSIZE_4B(PTR, len)
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#define SET_VARSIZE_SHORT(PTR, len) SET_VARSIZE_1B(PTR, len)
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#define SET_VARSIZE_COMPRESSED(PTR, len) SET_VARSIZE_4B_C(PTR, len)
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#define SET_VARSIZE_EXTERNAL(PTR) SET_VARSIZE_1B_E(PTR)
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#define SET_VARSIZE_EXTERNAL(PTR, len) SET_VARSIZE_1B_E(PTR, len)
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#define VARSIZE_ANY(PTR) \
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(VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR) : \
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@ -266,7 +276,7 @@ typedef struct
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VARSIZE_4B(PTR)))
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#define VARSIZE_ANY_EXHDR(PTR) \
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(VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR)-1 : \
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(VARATT_IS_1B_E(PTR) ? VARSIZE_1B_E(PTR)-2 : \
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(VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR)-1 : \
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VARSIZE_4B(PTR)-4))
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