* Client-side code should include postgres_fe.h instead.
*
*
- * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1995, Regents of the University of California
*
* src/include/postgres.h
* in the backend environment, but are of no interest outside the backend.
*
* Simple type definitions live in c.h, where they are shared with
- * postgres_fe.h. We do that since those type definitions are needed by
+ * postgres_fe.h. We do that since those type definitions are needed by
* frontend modules that want to deal with binary data transmission to or
* from the backend. Type definitions in this file should be for
* representations that never escape the backend, such as Datum or
*/
/*
- * 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.
+ * struct varatt_external is a traditional "TOAST pointer", that is, the
+ * information needed to fetch a Datum stored out-of-line in a TOAST table.
+ * The data is compressed if and only if va_extsize < va_rawsize - VARHDRSZ.
+ * This struct must not contain any padding, because we sometimes compare
+ * these 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
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;
+} 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.
+ * struct varatt_indirect is a "TOAST pointer" representing an out-of-line
+ * Datum that's stored in memory, not in an external toast relation.
+ * The creator of such a Datum is entirely responsible that the referenced
+ * storage survives for as long as referencing pointer Datums can exist.
*
- * Note that just as varatt_external's this is stored unaligned within the
- * tuple.
+ * Note that just as for struct varatt_external, this struct is stored
+ * unaligned within any containing tuple.
*/
typedef struct varatt_indirect
{
struct varlena *pointer; /* Pointer to in-memory varlena */
-} varatt_indirect;
-
+} 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...
+ * Type tag for the various sorts of "TOAST pointer" datums. The peculiar
+ * value for VARTAG_ONDISK comes from a requirement for on-disk compatibility
+ * with a previous notion that the tag field was the pointer datum's length.
*/
typedef enum vartag_external
{
} vartag_external;
#define VARTAG_SIZE(tag) \
- ((tag) == VARTAG_INDIRECT ? sizeof(varatt_indirect) : \
+ ((tag) == VARTAG_INDIRECT ? sizeof(varatt_indirect) : \
(tag) == VARTAG_ONDISK ? sizeof(varatt_external) : \
- TrapMacro(true, "unknown vartag"))
+ TrapMacro(true, "unrecognized TOAST vartag"))
/*
* These structs describe the header of a varlena object that may have been
struct /* Normal varlena (4-byte length) */
{
uint32 va_header;
- char va_data[1];
+ char va_data[FLEXIBLE_ARRAY_MEMBER];
} va_4byte;
struct /* Compressed-in-line format */
{
uint32 va_header;
uint32 va_rawsize; /* Original data size (excludes header) */
- char va_data[1]; /* Compressed data */
+ char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Compressed data */
} va_compressed;
} varattrib_4b;
typedef struct
{
uint8 va_header;
- char va_data[1]; /* Data begins here */
+ char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Data begins here */
} varattrib_1b;
-/* inline portion of a short varlena pointing to an external resource */
+/* TOAST pointers are a subset of varattrib_1b with an identifying tag byte */
typedef struct
{
uint8 va_header; /* Always 0x80 or 0x01 */
uint8 va_tag; /* Type of datum */
- char va_data[1]; /* Data (of the type indicated by va_tag) */
+ char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Type-specific data */
} varattrib_1b_e;
/*
* The "xxx" bits are the length field (which includes itself in all cases).
* In the big-endian case we mask to extract the length, in the little-endian
* case we shift. Note that in both cases the flag bits are in the physically
- * first byte. Also, it is not possible for a 1-byte length word to be zero;
+ * 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.
+ * In TOAST pointers the va_tag field (see varattrib_1b_e) is used to discern
+ * the specific type and length of the pointer datum.
*/
/*
*/
/*
- * These declarations supports the assertion-related macros in c.h.
- * assert_enabled is here because that file doesn't have PGDLLIMPORT in the
- * right place, and ExceptionalCondition must be present, for the backend only,
- * even when assertions are not enabled.
+ * Backend only infrastructure for the assertion-related macros in c.h.
+ *
+ * ExceptionalCondition must be present even when assertions are not enabled.
*/
-extern PGDLLIMPORT bool assert_enabled;
-
extern void ExceptionalCondition(const char *conditionName,
const char *errorType,
- const char *fileName, int lineNumber) __attribute__((noreturn));
+ const char *fileName, int lineNumber) pg_attribute_noreturn;
#endif /* POSTGRES_H */
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