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tableam: Move heap-specific logic from needs_toast_table below tableam.

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This allows table AMs to completely suppress TOAST table creation, or
to modify the conditions under which they are created.

Patch by me.  Reviewed by Andres Freund.

Discussion: http://postgr.es/m/CA+Tgmoa4O2n=yphqD2pERUnYmUO84bH1SqMsA-nSxBGsZ7gWfA@mail.gmail.com
This commit is contained in:
Robert Haas
2019-05-21 11:57:13 -04:00
parent cf92226e9f
commit 1171d7d585
3 changed files with 76 additions and 47 deletions
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53
src/backend/access/heap/heapam_handler.c
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@ -29,6 +29,7 @@
#include "access/rewriteheap.h"
#include "access/tableam.h"
#include "access/tsmapi.h"
#include "access/tuptoaster.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/index.h"
@ -2009,6 +2010,57 @@ heapam_relation_size(Relation rel, ForkNumber forkNumber)
return nblocks * BLCKSZ;
}
/*
* Check to see whether the table needs a TOAST table. It does only if
* (1) there are any toastable attributes, and (2) the maximum length
* of a tuple could exceed TOAST_TUPLE_THRESHOLD. (We don't want to
* create a toast table for something like "f1 varchar(20)".)
*/
static bool
heapam_relation_needs_toast_table(Relation rel)
{
int32 data_length = 0;
bool maxlength_unknown = false;
bool has_toastable_attrs = false;
TupleDesc tupdesc = rel->rd_att;
int32 tuple_length;
int i;
for (i = 0; i < tupdesc->natts; i++)
{
Form_pg_attribute att = TupleDescAttr(tupdesc, i);
if (att->attisdropped)
continue;
data_length = att_align_nominal(data_length, att->attalign);
if (att->attlen > 0)
{
/* Fixed-length types are never toastable */
data_length += att->attlen;
}
else
{
int32 maxlen = type_maximum_size(att->atttypid,
att->atttypmod);
if (maxlen < 0)
maxlength_unknown = true;
else
data_length += maxlen;
if (att->attstorage != 'p')
has_toastable_attrs = true;
}
}
if (!has_toastable_attrs)
return false; /* nothing to toast? */
if (maxlength_unknown)
return true; /* any unlimited-length attrs? */
tuple_length = MAXALIGN(SizeofHeapTupleHeader +
BITMAPLEN(tupdesc->natts)) +
MAXALIGN(data_length);
return (tuple_length > TOAST_TUPLE_THRESHOLD);
}
/* ------------------------------------------------------------------------
* Planner related callbacks for the heap AM
@ -2592,6 +2644,7 @@ static const TableAmRoutine heapam_methods = {
.index_validate_scan = heapam_index_validate_scan,
.relation_size = heapam_relation_size,
.relation_needs_toast_table = heapam_relation_needs_toast_table,
.relation_estimate_size = heapam_estimate_rel_size,