*/
typedef struct toast_compress_header
{
- int32 vl_len_; /* varlena header (do not touch directly!) */
+ int32 vl_len_; /* varlena header (do not touch directly!) */
int32 rawsize;
} toast_compress_header;
* Utilities for manipulation of header information for compressed
* toast entries.
*/
-#define TOAST_COMPRESS_HDRSZ ((int32) sizeof(toast_compress_header))
-#define TOAST_COMPRESS_RAWSIZE(ptr) (((toast_compress_header *) ptr)->rawsize)
+#define TOAST_COMPRESS_HDRSZ ((int32) sizeof(toast_compress_header))
+#define TOAST_COMPRESS_RAWSIZE(ptr) (((toast_compress_header *) (ptr))->rawsize)
#define TOAST_COMPRESS_RAWDATA(ptr) \
- (((char *) ptr) + TOAST_COMPRESS_HDRSZ)
+ (((char *) (ptr)) + TOAST_COMPRESS_HDRSZ)
#define TOAST_COMPRESS_SET_RAWSIZE(ptr, len) \
- (((toast_compress_header *) ptr)->rawsize = len)
+ (((toast_compress_header *) (ptr))->rawsize = (len))
static void toast_delete_datum(Relation rel, Datum value);
static Datum toast_save_datum(Relation rel, Datum value,
*
* This will return a datum that contains all the data internally, ie, not
* relying on external storage or memory, but it can still be compressed or
- * have a short header.
- ----------
+ * have a short header. Note some callers assume that if the input is an
+ * EXTERNAL datum, the result will be a pfree'able chunk.
+ * ----------
*/
struct varlena *
heap_tuple_fetch_attr(struct varlena * attr)
else if (VARATT_IS_EXTERNAL_INDIRECT(attr))
{
/*
- * copy into the caller's memory context. That's not required in all
- * cases but sufficient for now since this is mainly used when we need
- * to persist a Datum for unusually long time, like in a HOLD cursor.
+ * This is an indirect pointer --- dereference it
*/
struct varatt_indirect redirect;
/* nested indirect Datums aren't allowed */
Assert(!VARATT_IS_EXTERNAL_INDIRECT(attr));
- /* doesn't make much sense, but better handle it */
- if (VARATT_IS_EXTERNAL_ONDISK(attr))
+ /* recurse if value is still external in some other way */
+ if (VARATT_IS_EXTERNAL(attr))
return heap_tuple_fetch_attr(attr);
- /* copy datum verbatim */
+ /*
+ * Copy into the caller's memory context, in case caller tries to
+ * pfree the result.
+ */
result = (struct varlena *) palloc(VARSIZE_ANY(attr));
memcpy(result, attr, VARSIZE_ANY(attr));
}
* heap_tuple_untoast_attr -
*
* Public entry point to get back a toasted value from compression
- * or external storage.
+ * or external storage. The result is always non-extended varlena form.
+ *
+ * Note some callers assume that if the input is an EXTERNAL or COMPRESSED
+ * datum, the result will be a pfree'able chunk.
* ----------
*/
struct varlena *
if (VARATT_IS_COMPRESSED(attr))
{
struct varlena *tmp = attr;
+
attr = toast_decompress_datum(tmp);
pfree(tmp);
}
}
else if (VARATT_IS_EXTERNAL_INDIRECT(attr))
{
+ /*
+ * This is an indirect pointer --- dereference it
+ */
struct varatt_indirect redirect;
VARATT_EXTERNAL_GET_POINTER(redirect, attr);
/* nested indirect Datums aren't allowed */
Assert(!VARATT_IS_EXTERNAL_INDIRECT(attr));
+ /* recurse in case value is still extended in some other way */
attr = heap_tuple_untoast_attr(attr);
+
+ /* if it isn't, we'd better copy it */
+ if (attr == (struct varlena *) redirect.pointer)
+ {
+ struct varlena *result;
+
+ result = (struct varlena *) palloc(VARSIZE_ANY(attr));
+ memcpy(result, attr, VARSIZE_ANY(attr));
+ attr = result;
+ }
}
else if (VARATT_IS_COMPRESSED(attr))
{
else
preslice = attr;
+ Assert(!VARATT_IS_EXTERNAL(preslice));
+
if (VARATT_IS_COMPRESSED(preslice))
{
struct varlena *tmp = preslice;
+
preslice = toast_decompress_datum(tmp);
if (tmp != attr)
continue;
else if (VARATT_IS_EXTERNAL_ONDISK(PointerGetDatum(value)))
toast_delete_datum(rel, value);
- else if (VARATT_IS_EXTERNAL_INDIRECT(PointerGetDatum(value)))
- elog(ERROR, "attempt to delete tuple containing indirect datums");
}
}
}
/*
* We took care of UPDATE above, so any external value we find
- * still in the tuple must be someone else's we cannot reuse.
+ * still in the tuple must be someone else's that we cannot reuse
+ * (this includes the case of an out-of-line in-memory datum).
* Fetch it back (without decompression, unless we are forcing
* PLAIN storage). If necessary, we'll push it out as a new
* external value below.
new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
if (VARATT_IS_EXTERNAL(new_value))
{
- new_value = toast_fetch_datum(new_value);
+ new_value = heap_tuple_fetch_attr(new_value);
toast_values[i] = PointerGetDatum(new_value);
toast_free[i] = true;
}
int num_indexes;
int validIndex;
- if (VARATT_IS_EXTERNAL_INDIRECT(attr))
- elog(ERROR, "shouldn't be called for indirect tuples");
+ if (!VARATT_IS_EXTERNAL_ONDISK(attr))
+ elog(ERROR, "toast_fetch_datum shouldn't be called for non-ondisk datums");
/* Must copy to access aligned fields */
VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
int num_indexes;
int validIndex;
- Assert(VARATT_IS_EXTERNAL_ONDISK(attr));
+ if (!VARATT_IS_EXTERNAL_ONDISK(attr))
+ elog(ERROR, "toast_fetch_datum_slice shouldn't be called for non-ondisk datums");
/* Must copy to access aligned fields */
VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
*/
/*
- * 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
} 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;
-
/*
- * 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
char va_data[1]; /* 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 */
* 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.
*/
/*
projects / users / rhaas / postgres.git / commitdiff