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Minor cleanup/code review for "indirect toast" stuff.

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Fix some issues I noticed while fooling with an extension to allow an
additional kind of toast pointer.  Much of this is just comment
improvement, but there are a couple of actual bugs, which might or might
not be reachable today depending on what can happen during logical
decoding.  An example is that toast_flatten_tuple() failed to cover the
possibility of an indirection pointer in its input.  Back-patch to 9.4
just in case that is reachable now.

In HEAD, also correct some really minor issues with recent compression
reorganization, such as dangerously underparenthesized macros.
This commit is contained in:
Tom Lane
2015-02-09 12:30:52 -05:00
parent c619c2351f
commit bc4de01db3
3 changed files with 66 additions and 42 deletions
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65
src/backend/access/heap/tuptoaster.c
View File

@ -50,7 +50,7 @@
*/
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;
@ -58,12 +58,12 @@ typedef struct 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,
@ -90,8 +90,9 @@ static void toast_close_indexes(Relation *toastidxs, int num_indexes,
*
* 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)
@ -108,9 +109,7 @@ 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;
@ -120,11 +119,14 @@ heap_tuple_fetch_attr(struct varlena * attr)
/* 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));
}
@ -144,7 +146,10 @@ heap_tuple_fetch_attr(struct varlena * 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 *
@ -160,12 +165,16 @@ heap_tuple_untoast_attr(struct varlena * attr)
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);
@ -174,7 +183,18 @@ heap_tuple_untoast_attr(struct varlena * 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))
{
@ -246,9 +266,12 @@ heap_tuple_untoast_attr_slice(struct varlena * 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)
@ -448,8 +471,6 @@ toast_delete(Relation rel, HeapTuple oldtup)
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");
}
}
}
@ -611,7 +632,8 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
/*
* 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.
@ -1043,7 +1065,7 @@ toast_flatten_tuple(HeapTuple tup, TupleDesc tupleDesc)
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;
}
@ -1746,8 +1768,8 @@ toast_fetch_datum(struct varlena * attr)
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);
@ -1923,7 +1945,8 @@ toast_fetch_datum_slice(struct varlena * attr, int32 sliceoffset, int32 length)
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);