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Some small tuptoaster improvements from Greg Stark. Avoid unnecessary

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decompression of an already-compressed external value when we have to copy
it; save a few cycles when a value is too short for compression; and
annotate various lines that are currently unreachable.
This commit is contained in:
Tom Lane 2007-09-26 23:29:10 +00:00
parent f18dfc4835
commit 84fe8990ae
1 changed files with 26 additions and 7 deletions
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33
src/backend/access/heap/tuptoaster.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.74 2007/04/06 04:21:41 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.75 2007/09/26 23:29:10 tgl Exp $
*
*
* INTERFACE ROUTINES
@ -525,11 +525,16 @@ 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.
* Expand it to plain (and, probably, toast it again below).
* Fetch it back (without decompression, unless we are forcing
* PLAIN storage). If necessary, we'll push it out as a new
* external value below.
*/
if (VARATT_IS_EXTERNAL(new_value))
{
new_value = heap_tuple_untoast_attr(new_value);
if (att[i]->attstorage == 'p')
new_value = heap_tuple_untoast_attr(new_value);
else
new_value = heap_tuple_fetch_attr(new_value);
toast_values[i] = PointerGetDatum(new_value);
toast_free[i] = true;
need_change = true;
@ -590,7 +595,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
if (toast_action[i] != ' ')
continue;
if (VARATT_IS_EXTERNAL(toast_values[i]))
continue;
continue; /* can't happen, toast_action would be 'p' */
if (VARATT_IS_COMPRESSED(toast_values[i]))
continue;
if (att[i]->attstorage != 'x')
@ -654,7 +659,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
if (toast_action[i] == 'p')
continue;
if (VARATT_IS_EXTERNAL(toast_values[i]))
continue;
continue; /* can't happen, toast_action would be 'p' */
if (att[i]->attstorage != 'x' && att[i]->attstorage != 'e')
continue;
if (toast_sizes[i] > biggest_size)
@ -703,7 +708,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
if (toast_action[i] != ' ')
continue;
if (VARATT_IS_EXTERNAL(toast_values[i]))
continue;
continue; /* can't happen, toast_action would be 'p' */
if (VARATT_IS_COMPRESSED(toast_values[i]))
continue;
if (att[i]->attstorage != 'm')
@ -766,7 +771,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
if (toast_action[i] == 'p')
continue;
if (VARATT_IS_EXTERNAL(toast_values[i]))
continue;
continue; /* can't happen, toast_action would be 'p' */
if (att[i]->attstorage != 'm')
continue;
if (toast_sizes[i] > biggest_size)
@ -1025,6 +1030,12 @@ toast_compress_datum(Datum value)
Assert(!VARATT_IS_EXTERNAL(value));
Assert(!VARATT_IS_COMPRESSED(value));
/*
* No point in wasting a palloc cycle if value is too short for compression
*/
if (valsize < PGLZ_strategy_default->min_input_size)
return PointerGetDatum(NULL);
tmp = (struct varlena *) palloc(PGLZ_MAX_OUTPUT(valsize));
if (pglz_compress(VARDATA_ANY(value), valsize,
(PGLZ_Header *) tmp, PGLZ_strategy_default) &&
@ -1438,10 +1449,18 @@ toast_fetch_datum_slice(struct varlena *attr, int32 sliceoffset, int32 length)
int32 chcpystrt;
int32 chcpyend;
Assert(VARATT_IS_EXTERNAL(attr));
/* Must copy to access aligned fields */
memcpy(&toast_pointer, VARDATA_SHORT(attr),
sizeof(struct varatt_external));
/*
* It's nonsense to fetch slices of a compressed datum -- this isn't lo_*
* we can't return a compressed datum which is meaningful to toast later
*/
Assert(!VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer));
attrsize = toast_pointer.va_extsize;
totalchunks = ((attrsize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;