83 lines
2.4 KiB
C
83 lines
2.4 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* detoast.h
|
|
* Access to compressed and external varlena values.
|
|
*
|
|
* Copyright (c) 2000-2024, PostgreSQL Global Development Group
|
|
*
|
|
* src/include/access/detoast.h
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
#ifndef DETOAST_H
|
|
#define DETOAST_H
|
|
|
|
/*
|
|
* 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)
|
|
|
|
/* Size of an EXTERNAL datum that contains a standard TOAST pointer */
|
|
#define TOAST_POINTER_SIZE (VARHDRSZ_EXTERNAL + sizeof(varatt_external))
|
|
|
|
/* Size of an EXTERNAL datum that contains an indirection pointer */
|
|
#define INDIRECT_POINTER_SIZE (VARHDRSZ_EXTERNAL + sizeof(varatt_indirect))
|
|
|
|
/* ----------
|
|
* detoast_external_attr() -
|
|
*
|
|
* Fetches an external stored attribute from the toast
|
|
* relation. Does NOT decompress it, if stored external
|
|
* in compressed format.
|
|
* ----------
|
|
*/
|
|
extern struct varlena *detoast_external_attr(struct varlena *attr);
|
|
|
|
/* ----------
|
|
* detoast_attr() -
|
|
*
|
|
* Fully detoasts one attribute, fetching and/or decompressing
|
|
* it as needed.
|
|
* ----------
|
|
*/
|
|
extern struct varlena *detoast_attr(struct varlena *attr);
|
|
|
|
/* ----------
|
|
* detoast_attr_slice() -
|
|
*
|
|
* Fetches only the specified portion of an attribute.
|
|
* (Handles all cases for attribute storage)
|
|
* ----------
|
|
*/
|
|
extern struct varlena *detoast_attr_slice(struct varlena *attr,
|
|
int32 sliceoffset,
|
|
int32 slicelength);
|
|
|
|
/* ----------
|
|
* toast_raw_datum_size -
|
|
*
|
|
* Return the raw (detoasted) size of a varlena datum
|
|
* ----------
|
|
*/
|
|
extern Size toast_raw_datum_size(Datum value);
|
|
|
|
/* ----------
|
|
* toast_datum_size -
|
|
*
|
|
* Return the storage size of a varlena datum
|
|
* ----------
|
|
*/
|
|
extern Size toast_datum_size(Datum value);
|
|
|
|
#endif /* DETOAST_H */
|