Although we can't support out-of-line TOAST storage in indexes (yet),
compressed storage works perfectly well. Might as well have a coherent strategy for applying it, rather than the haphazard store-what-you-get approach that was in the code before. The strategy I've set up here is to attempt compression of any compressible index value exceeding BLCKSZ/16, or about 500 bytes by default.
This commit is contained in:
Tom Lane
parent
5341cddba8
commit
059e361481
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@ -2,14 +2,14 @@
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*
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* indextuple.c
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* This file contains index tuple accessor and mutator routines,
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* as well as a few various tuple utilities.
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* as well as various tuple utilities.
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*
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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/access/common/indextuple.c,v 1.50 2001/01/24 19:42:47 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/access/common/indextuple.c,v 1.51 2001/02/15 20:57:01 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -57,25 +57,45 @@ index_formtuple(TupleDesc tupleDescriptor,
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#ifdef TOAST_INDEX_HACK
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for (i = 0; i < numberOfAttributes; i++)
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{
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if (null[i] != ' ' || tupleDescriptor->attrs[i]->attlen >= 0)
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Form_pg_attribute att = tupleDescriptor->attrs[i];
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untoasted_value[i] = value[i];
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untoasted_free[i] = false;
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/* Do nothing if value is NULL or not of varlena type */
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if (null[i] != ' ' || att->attlen >= 0)
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continue;
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/*
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* If value is stored EXTERNAL, must fetch it so we are not
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* depending on outside storage. This should be improved someday.
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*/
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if (VARATT_IS_EXTERNAL(value[i]))
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{
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untoasted_value[i] = value[i];
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untoasted_free[i] = false;
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untoasted_value[i] = PointerGetDatum(
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heap_tuple_fetch_attr(
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(varattrib *) DatumGetPointer(value[i])));
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untoasted_free[i] = true;
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}
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else
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/*
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* If value is above size target, and is of a compressible datatype,
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* try to compress it in-line.
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*/
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if (VARATT_SIZE(untoasted_value[i]) > TOAST_INDEX_TARGET &&
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!VARATT_IS_EXTENDED(untoasted_value[i]) &&
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(att->attstorage == 'x' || att->attstorage == 'm'))
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{
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if (VARATT_IS_EXTERNAL(value[i]))
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Datum cvalue = toast_compress_datum(untoasted_value[i]);
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if (DatumGetPointer(cvalue) != NULL)
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{
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untoasted_value[i] = PointerGetDatum(
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heap_tuple_fetch_attr(
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(varattrib *)DatumGetPointer(value[i])));
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/* successful compression */
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if (untoasted_free[i])
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pfree(DatumGetPointer(untoasted_value[i]));
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untoasted_value[i] = cvalue;
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untoasted_free[i] = true;
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}
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else
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{
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untoasted_value[i] = value[i];
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untoasted_free[i] = false;
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}
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}
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}
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#endif
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@ -137,10 +157,9 @@ index_formtuple(TupleDesc tupleDescriptor,
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* Here we make sure that the size will fit in the field reserved for
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* it in t_info.
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*/
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if ((size & INDEX_SIZE_MASK) != size)
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elog(ERROR, "index_formtuple: data takes %lu bytes: too big",
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(unsigned long)size);
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elog(ERROR, "index_formtuple: data takes %lu bytes, max is %d",
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(unsigned long) size, INDEX_SIZE_MASK);
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infomask |= size;
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.16 2001/02/09 17:30:03 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.17 2001/02/15 20:57:01 tgl Exp $
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*
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*
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* INTERFACE ROUTINES
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@ -45,7 +45,6 @@ static void toast_delete(Relation rel, HeapTuple oldtup);
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static void toast_delete_datum(Relation rel, Datum value);
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static void toast_insert_or_update(Relation rel, HeapTuple newtup,
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HeapTuple oldtup);
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static Datum toast_compress_datum(Datum value);
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static Datum toast_save_datum(Relation rel, Oid mainoid, int16 attno, Datum value);
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static varattrib *toast_fetch_datum(varattrib *attr);
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@ -721,7 +720,7 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup)
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* the tuple!
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* ----------
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*/
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static Datum
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Datum
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toast_compress_datum(Datum value)
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{
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varattrib *tmp;
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@ -6,7 +6,7 @@
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*
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* Copyright (c) 2000, PostgreSQL Development Team
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*
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* $Id: tuptoaster.h,v 1.8 2000/08/04 04:16:10 tgl Exp $
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* $Id: tuptoaster.h,v 1.9 2001/02/15 20:57:01 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -40,6 +40,12 @@
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#define TOAST_TUPLE_TARGET (MaxTupleSize / 4)
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/*
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* If an index value is larger than TOAST_INDEX_TARGET, we will try to
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* compress it (we can't move it out-of-line, however). Note that this
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* number is per-datum, not per-tuple, for simplicity in index_formtuple().
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*/
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#define TOAST_INDEX_TARGET (MaxTupleSize / 16)
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/*
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* When we store an oversize datum externally, we divide it into chunks
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@ -95,6 +101,14 @@ extern varattrib *heap_tuple_fetch_attr(varattrib * attr);
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*/
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extern varattrib *heap_tuple_untoast_attr(varattrib * attr);
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/* ----------
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* toast_compress_datum -
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*
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* Create a compressed version of a varlena datum, if possible
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* ----------
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*/
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extern Datum toast_compress_datum(Datum value);
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#endif /* TUPLE_TOASTER_ACTIVE */
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