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Replace uses of SPI_modifytuple that intend to allocate in current context.

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Invent a new function heap_modify_tuple_by_cols() that is functionally
equivalent to SPI_modifytuple except that it always allocates its result
by simple palloc.  I chose however to make the API details a bit more
like heap_modify_tuple: pass a tupdesc rather than a Relation, and use
bool convention for the isnull array.

Use this function in place of SPI_modifytuple at all call sites where the
intended behavior is to allocate in current context.  (There actually are
only two call sites left that depend on the old behavior, which makes me
wonder if we should just drop this function rather than keep it.)

This new function is easier to use than heap_modify_tuple() for purposes
of replacing a single column (or, really, any fixed number of columns).
There are a number of places where it would simplify the code to change
over, but I resisted that temptation for the moment ... everywhere except
in plpgsql's exec_assign_value(); changing that might offer some small
performance benefit, so I did it.

This is on the way to removing SPI_push/SPI_pop, but it seems like
good code cleanup in its own right.

Discussion: <9633.1478552022@sss.pgh.pa.us>
This commit is contained in:
Tom Lane
2016-11-08 15:36:36 -05:00
parent dce429b117
commit 9257f07872
10 changed files with 136 additions and 94 deletions
Download Patch File Download Diff File Expand all files Collapse all files

66
src/backend/access/common/heaptuple.c
View File

@ -846,6 +846,72 @@ heap_modify_tuple(HeapTuple tuple,
return newTuple;
}
/*
* heap_modify_tuple_by_cols
* form a new tuple from an old tuple and a set of replacement values.
*
* This is like heap_modify_tuple, except that instead of specifying which
* column(s) to replace by a boolean map, an array of target column numbers
* is used. This is often more convenient when a fixed number of columns
* are to be replaced. The replCols, replValues, and replIsnull arrays must
* be of length nCols. Target column numbers are indexed from 1.
*
* The result is allocated in the current memory context.
*/
HeapTuple
heap_modify_tuple_by_cols(HeapTuple tuple,
TupleDesc tupleDesc,
int nCols,
int *replCols,
Datum *replValues,
bool *replIsnull)
{
int numberOfAttributes = tupleDesc->natts;
Datum *values;
bool *isnull;
HeapTuple newTuple;
int i;
/*
* allocate and fill values and isnull arrays from the tuple, then replace
* selected columns from the input arrays.
*/
values = (Datum *) palloc(numberOfAttributes * sizeof(Datum));
isnull = (bool *) palloc(numberOfAttributes * sizeof(bool));
heap_deform_tuple(tuple, tupleDesc, values, isnull);
for (i = 0; i < nCols; i++)
{
int attnum = replCols[i];
if (attnum <= 0 || attnum > numberOfAttributes)
elog(ERROR, "invalid column number %d", attnum);
values[attnum - 1] = replValues[i];
isnull[attnum - 1] = replIsnull[i];
}
/*
* create a new tuple from the values and isnull arrays
*/
newTuple = heap_form_tuple(tupleDesc, values, isnull);
pfree(values);
pfree(isnull);
/*
* copy the identification info of the old tuple: t_ctid, t_self, and OID
* (if any)
*/
newTuple->t_data->t_ctid = tuple->t_data->t_ctid;
newTuple->t_self = tuple->t_self;
newTuple->t_tableOid = tuple->t_tableOid;
if (tupleDesc->tdhasoid)
HeapTupleSetOid(newTuple, HeapTupleGetOid(tuple));
return newTuple;
}
/*
* heap_deform_tuple
* Given a tuple, extract data into values/isnull arrays; this is

16
src/backend/utils/adt/tsvector_op.c
View File

@ -2329,8 +2329,10 @@ tsvector_update_trigger(PG_FUNCTION_ARGS, bool config_column)
if (prs.curwords)
{
datum = PointerGetDatum(make_tsvector(&prs));
rettuple = SPI_modifytuple(rel, rettuple, 1, &tsvector_attr_num,
&datum, NULL);
isnull = false;
rettuple = heap_modify_tuple_by_cols(rettuple, rel->rd_att,
1, &tsvector_attr_num,
&datum, &isnull);
pfree(DatumGetPointer(datum));
}
else
@ -2340,14 +2342,12 @@ tsvector_update_trigger(PG_FUNCTION_ARGS, bool config_column)
SET_VARSIZE(out, CALCDATASIZE(0, 0));
out->size = 0;
datum = PointerGetDatum(out);
rettuple = SPI_modifytuple(rel, rettuple, 1, &tsvector_attr_num,
&datum, NULL);
isnull = false;
rettuple = heap_modify_tuple_by_cols(rettuple, rel->rd_att,
1, &tsvector_attr_num,
&datum, &isnull);
pfree(prs.words);
}
if (rettuple == NULL) /* internal error */
elog(ERROR, "tsvector_update_trigger: %d returned by SPI_modifytuple",
SPI_result);
return PointerGetDatum(rettuple);
}

6
src/include/access/htup_details.h
View File

@ -805,6 +805,12 @@ extern HeapTuple heap_modify_tuple(HeapTuple tuple,
Datum *replValues,
bool *replIsnull,
bool *doReplace);
extern HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple,
TupleDesc tupleDesc,
int nCols,
int *replCols,
Datum *replValues,
bool *replIsnull);
extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
Datum *values, bool *isnull);
extern void heap_freetuple(HeapTuple htup);

55
src/pl/plpgsql/src/pl_exec.c
View File

@ -4562,10 +4562,9 @@ exec_assign_value(PLpgSQL_execstate *estate,
PLpgSQL_rec *rec;
int fno;
HeapTuple newtup;
int natts;
Datum *values;
bool *nulls;
bool *replaces;
int colnums[1];
Datum values[1];
bool nulls[1];
Oid atttype;
int32 atttypmod;
@ -4584,9 +4583,8 @@ exec_assign_value(PLpgSQL_execstate *estate,
errdetail("The tuple structure of a not-yet-assigned record is indeterminate.")));
/*
* Get the number of the records field to change and the
* number of attributes in the tuple. Note: disallow system
* column names because the code below won't cope.
* Get the number of the record field to change. Disallow
* system columns because the code below won't cope.
*/
fno = SPI_fnumber(rec->tupdesc, recfield->fieldname);
if (fno <= 0)
@ -4594,42 +4592,25 @@ exec_assign_value(PLpgSQL_execstate *estate,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("record \"%s\" has no field \"%s\"",
rec->refname, recfield->fieldname)));
fno--;
natts = rec->tupdesc->natts;
/*
* Set up values/control arrays for heap_modify_tuple. For all
* the attributes except the one we want to replace, use the
* value that's in the old tuple.
*/
values = eval_mcontext_alloc(estate, sizeof(Datum) * natts);
nulls = eval_mcontext_alloc(estate, sizeof(bool) * natts);
replaces = eval_mcontext_alloc(estate, sizeof(bool) * natts);
memset(replaces, false, sizeof(bool) * natts);
replaces[fno] = true;
colnums[0] = fno;
/*
* Now insert the new value, being careful to cast it to the
* right type.
*/
atttype = rec->tupdesc->attrs[fno]->atttypid;
atttypmod = rec->tupdesc->attrs[fno]->atttypmod;
values[fno] = exec_cast_value(estate,
value,
&isNull,
valtype,
valtypmod,
atttype,
atttypmod);
nulls[fno] = isNull;
atttype = rec->tupdesc->attrs[fno - 1]->atttypid;
atttypmod = rec->tupdesc->attrs[fno - 1]->atttypmod;
values[0] = exec_cast_value(estate,
value,
&isNull,
valtype,
valtypmod,
atttype,
atttypmod);
nulls[0] = isNull;
/*
* Now call heap_modify_tuple() to create a new tuple that
* replaces the old one in the record.
*/
newtup = heap_modify_tuple(rec->tup, rec->tupdesc,
values, nulls, replaces);
newtup = heap_modify_tuple_by_cols(rec->tup, rec->tupdesc,
1, colnums, values, nulls);
if (rec->freetup)
heap_freetuple(rec->tup);

11
src/test/regress/regress.c
View File

@ -639,15 +639,8 @@ ttdummy(PG_FUNCTION_ARGS)
/* Tuple to return to upper Executor ... */
if (newtuple) /* UPDATE */
{
HeapTuple tmptuple;
tmptuple = SPI_copytuple(trigtuple);
rettuple = SPI_modifytuple(rel, tmptuple, 1, &(attnum[1]), &newoff, NULL);
SPI_freetuple(tmptuple);
}
else
/* DELETE */
rettuple = SPI_modifytuple(rel, trigtuple, 1, &(attnum[1]), &newoff, NULL);
else /* DELETE */
rettuple = trigtuple;
SPI_finish(); /* don't forget say Bye to SPI mgr */