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Redesign get_attstatsslot()/free_attstatsslot() for more safety and speed.

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The mess cleaned up in commit da0759600 is clear evidence that it's a
bug hazard to expect the caller of get_attstatsslot()/free_attstatsslot()
to provide the correct type OID for the array elements in the slot.
Moreover, we weren't even getting any performance benefit from that,
since get_attstatsslot() was extracting the real type OID from the array
anyway.  So we ought to get rid of that requirement; indeed, it would
make more sense for get_attstatsslot() to pass back the type OID it found,
in case the caller isn't sure what to expect, which is likely in binary-
compatible-operator cases.

Another problem with the current implementation is that if the stats array
element type is pass-by-reference, we incur a palloc/memcpy/pfree cycle
for each element.  That seemed acceptable when the code was written because
we were targeting O(10) array sizes --- but these days, stats arrays are
almost always bigger than that, sometimes much bigger.  We can save a
significant number of cycles by doing one palloc/memcpy/pfree of the whole
array.  Indeed, in the now-probably-common case where the array is toasted,
that happens anyway so this method is basically free.  (Note: although the
catcache code will inline any out-of-line toasted values, it doesn't
decompress them.  At the other end of the size range, it doesn't expand
short-header datums either.  In either case, DatumGetArrayTypeP would have
to make a copy.  We do end up using an extra array copy step if the element
type is pass-by-value and the array length is neither small enough for a
short header nor large enough to have suffered compression.  But that
seems like a very acceptable price for winning in pass-by-ref cases.)

Hence, redesign to take these insights into account.  While at it,
convert to an API in which we fill a struct rather than passing a bunch
of pointers to individual output arguments.  That will make it less
painful if we ever want further expansion of what get_attstatsslot can
pass back.

It's certainly arguable that this is new development and not something to
push post-feature-freeze.  However, I view it as primarily bug-proofing
and therefore something that's better to have sooner not later.  Since
we aren't quite at beta phase yet, let's put it in.

Discussion: https://postgr.es/m/16364.1494520862@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2017-05-13 15:14:39 -04:00
parent 1848b73d45
commit 9aab83fc50
10 changed files with 434 additions and 599 deletions
Download Patch File Download Diff File Expand all files Collapse all files

214
src/backend/utils/adt/network_selfuncs.c
View File

@@ -88,10 +88,9 @@ networksel(PG_FUNCTION_ARGS)
Selectivity selec,
mcv_selec,
non_mcv_selec;
Datum constvalue,
*hist_values;
int hist_nvalues;
Datum constvalue;
Form_pg_statistic stats;
AttStatsSlot hslot;
double sumcommon,
nullfrac;
FmgrInfo proc;
@@ -146,22 +145,19 @@ networksel(PG_FUNCTION_ARGS)
* non-MCV population that satisfies the clause. If we don't, apply the
* default selectivity to that population.
*/
if (get_attstatsslot(vardata.statsTuple,
vardata.atttype, vardata.atttypmod,
if (get_attstatsslot(&hslot, vardata.statsTuple,
STATISTIC_KIND_HISTOGRAM, InvalidOid,
NULL,
&hist_values, &hist_nvalues,
NULL, NULL))
ATTSTATSSLOT_VALUES))
{
int opr_codenum = inet_opr_codenum(operator);
/* Commute if needed, so we can consider histogram to be on the left */
if (!varonleft)
opr_codenum = -opr_codenum;
non_mcv_selec = inet_hist_value_sel(hist_values, hist_nvalues,
non_mcv_selec = inet_hist_value_sel(hslot.values, hslot.nvalues,
constvalue, opr_codenum);
free_attstatsslot(vardata.atttype, hist_values, hist_nvalues, NULL, 0);
free_attstatsslot(&hslot);
}
else
non_mcv_selec = DEFAULT_SEL(operator);
@@ -277,42 +273,33 @@ networkjoinsel_inner(Oid operator,
hist1_exists = false,
hist2_exists = false;
int opr_codenum;
int mcv1_nvalues,
mcv2_nvalues,
mcv1_nnumbers,
mcv2_nnumbers,
hist1_nvalues,
hist2_nvalues,
mcv1_length = 0,
int mcv1_length = 0,
mcv2_length = 0;
Datum *mcv1_values,
*mcv2_values,
*hist1_values,
*hist2_values;
float4 *mcv1_numbers,
*mcv2_numbers;
AttStatsSlot mcv1_slot;
AttStatsSlot mcv2_slot;
AttStatsSlot hist1_slot;
AttStatsSlot hist2_slot;
if (HeapTupleIsValid(vardata1->statsTuple))
{
stats = (Form_pg_statistic) GETSTRUCT(vardata1->statsTuple);
nullfrac1 = stats->stanullfrac;
mcv1_exists = get_attstatsslot(vardata1->statsTuple,
vardata1->atttype, vardata1->atttypmod,
mcv1_exists = get_attstatsslot(&mcv1_slot, vardata1->statsTuple,
STATISTIC_KIND_MCV, InvalidOid,
NULL,
&mcv1_values, &mcv1_nvalues,
&mcv1_numbers, &mcv1_nnumbers);
hist1_exists = get_attstatsslot(vardata1->statsTuple,
vardata1->atttype, vardata1->atttypmod,
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS);
hist1_exists = get_attstatsslot(&hist1_slot, vardata1->statsTuple,
STATISTIC_KIND_HISTOGRAM, InvalidOid,
NULL,
&hist1_values, &hist1_nvalues,
NULL, NULL);
ATTSTATSSLOT_VALUES);
/* Arbitrarily limit number of MCVs considered */
mcv1_length = Min(mcv1_nvalues, MAX_CONSIDERED_ELEMS);
mcv1_length = Min(mcv1_slot.nvalues, MAX_CONSIDERED_ELEMS);
if (mcv1_exists)
sumcommon1 = mcv_population(mcv1_numbers, mcv1_length);
sumcommon1 = mcv_population(mcv1_slot.numbers, mcv1_length);
}
else
{
memset(&mcv1_slot, 0, sizeof(mcv1_slot));
memset(&hist1_slot, 0, sizeof(hist1_slot));
}
if (HeapTupleIsValid(vardata2->statsTuple))
@@ -320,22 +307,21 @@ networkjoinsel_inner(Oid operator,
stats = (Form_pg_statistic) GETSTRUCT(vardata2->statsTuple);
nullfrac2 = stats->stanullfrac;
mcv2_exists = get_attstatsslot(vardata2->statsTuple,
vardata2->atttype, vardata2->atttypmod,
mcv2_exists = get_attstatsslot(&mcv2_slot, vardata2->statsTuple,
STATISTIC_KIND_MCV, InvalidOid,
NULL,
&mcv2_values, &mcv2_nvalues,
&mcv2_numbers, &mcv2_nnumbers);
hist2_exists = get_attstatsslot(vardata2->statsTuple,
vardata2->atttype, vardata2->atttypmod,
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS);
hist2_exists = get_attstatsslot(&hist2_slot, vardata2->statsTuple,
STATISTIC_KIND_HISTOGRAM, InvalidOid,
NULL,
&hist2_values, &hist2_nvalues,
NULL, NULL);
ATTSTATSSLOT_VALUES);
/* Arbitrarily limit number of MCVs considered */
mcv2_length = Min(mcv2_nvalues, MAX_CONSIDERED_ELEMS);
mcv2_length = Min(mcv2_slot.nvalues, MAX_CONSIDERED_ELEMS);
if (mcv2_exists)
sumcommon2 = mcv_population(mcv2_numbers, mcv2_length);
sumcommon2 = mcv_population(mcv2_slot.numbers, mcv2_length);
}
else
{
memset(&mcv2_slot, 0, sizeof(mcv2_slot));
memset(&hist2_slot, 0, sizeof(hist2_slot));
}
opr_codenum = inet_opr_codenum(operator);
@@ -344,8 +330,10 @@ networkjoinsel_inner(Oid operator,
* Calculate selectivity for MCV vs MCV matches.
*/
if (mcv1_exists && mcv2_exists)
selec += inet_mcv_join_sel(mcv1_values, mcv1_numbers, mcv1_length,
mcv2_values, mcv2_numbers, mcv2_length,
selec += inet_mcv_join_sel(mcv1_slot.values, mcv1_slot.numbers,
mcv1_length,
mcv2_slot.values, mcv2_slot.numbers,
mcv2_length,
operator);
/*
@@ -355,13 +343,13 @@ networkjoinsel_inner(Oid operator,
*/
if (mcv1_exists && hist2_exists)
selec += (1.0 - nullfrac2 - sumcommon2) *
inet_mcv_hist_sel(mcv1_values, mcv1_numbers, mcv1_length,
hist2_values, hist2_nvalues,
inet_mcv_hist_sel(mcv1_slot.values, mcv1_slot.numbers, mcv1_length,
hist2_slot.values, hist2_slot.nvalues,
opr_codenum);
if (mcv2_exists && hist1_exists)
selec += (1.0 - nullfrac1 - sumcommon1) *
inet_mcv_hist_sel(mcv2_values, mcv2_numbers, mcv2_length,
hist1_values, hist1_nvalues,
inet_mcv_hist_sel(mcv2_slot.values, mcv2_slot.numbers, mcv2_length,
hist1_slot.values, hist1_slot.nvalues,
-opr_codenum);
/*
@@ -371,8 +359,8 @@ networkjoinsel_inner(Oid operator,
if (hist1_exists && hist2_exists)
selec += (1.0 - nullfrac1 - sumcommon1) *
(1.0 - nullfrac2 - sumcommon2) *
inet_hist_inclusion_join_sel(hist1_values, hist1_nvalues,
hist2_values, hist2_nvalues,
inet_hist_inclusion_join_sel(hist1_slot.values, hist1_slot.nvalues,
hist2_slot.values, hist2_slot.nvalues,
opr_codenum);
/*
@@ -383,18 +371,10 @@ networkjoinsel_inner(Oid operator,
selec = (1.0 - nullfrac1) * (1.0 - nullfrac2) * DEFAULT_SEL(operator);
/* Release stats. */
if (mcv1_exists)
free_attstatsslot(vardata1->atttype, mcv1_values, mcv1_nvalues,
mcv1_numbers, mcv1_nnumbers);
if (mcv2_exists)
free_attstatsslot(vardata2->atttype, mcv2_values, mcv2_nvalues,
mcv2_numbers, mcv2_nnumbers);
if (hist1_exists)
free_attstatsslot(vardata1->atttype, hist1_values, hist1_nvalues,
NULL, 0);
if (hist2_exists)
free_attstatsslot(vardata2->atttype, hist2_values, hist2_nvalues,
NULL, 0);
free_attstatsslot(&mcv1_slot);
free_attstatsslot(&mcv2_slot);
free_attstatsslot(&hist1_slot);
free_attstatsslot(&hist2_slot);
return selec;
}
@@ -423,42 +403,33 @@ networkjoinsel_semi(Oid operator,
int opr_codenum;
FmgrInfo proc;
int i,
mcv1_nvalues,
mcv2_nvalues,
mcv1_nnumbers,
mcv2_nnumbers,
hist1_nvalues,
hist2_nvalues,
mcv1_length = 0,
mcv2_length = 0;
Datum *mcv1_values,
*mcv2_values,
*hist1_values,
*hist2_values;
float4 *mcv1_numbers,
*mcv2_numbers;
AttStatsSlot mcv1_slot;
AttStatsSlot mcv2_slot;
AttStatsSlot hist1_slot;
AttStatsSlot hist2_slot;
if (HeapTupleIsValid(vardata1->statsTuple))
{
stats = (Form_pg_statistic) GETSTRUCT(vardata1->statsTuple);
nullfrac1 = stats->stanullfrac;
mcv1_exists = get_attstatsslot(vardata1->statsTuple,
vardata1->atttype, vardata1->atttypmod,
mcv1_exists = get_attstatsslot(&mcv1_slot, vardata1->statsTuple,
STATISTIC_KIND_MCV, InvalidOid,
NULL,
&mcv1_values, &mcv1_nvalues,
&mcv1_numbers, &mcv1_nnumbers);
hist1_exists = get_attstatsslot(vardata1->statsTuple,
vardata1->atttype, vardata1->atttypmod,
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS);
hist1_exists = get_attstatsslot(&hist1_slot, vardata1->statsTuple,
STATISTIC_KIND_HISTOGRAM, InvalidOid,
NULL,
&hist1_values, &hist1_nvalues,
NULL, NULL);
ATTSTATSSLOT_VALUES);
/* Arbitrarily limit number of MCVs considered */
mcv1_length = Min(mcv1_nvalues, MAX_CONSIDERED_ELEMS);
mcv1_length = Min(mcv1_slot.nvalues, MAX_CONSIDERED_ELEMS);
if (mcv1_exists)
sumcommon1 = mcv_population(mcv1_numbers, mcv1_length);
sumcommon1 = mcv_population(mcv1_slot.numbers, mcv1_length);
}
else
{
memset(&mcv1_slot, 0, sizeof(mcv1_slot));
memset(&hist1_slot, 0, sizeof(hist1_slot));
}
if (HeapTupleIsValid(vardata2->statsTuple))
@@ -466,22 +437,21 @@ networkjoinsel_semi(Oid operator,
stats = (Form_pg_statistic) GETSTRUCT(vardata2->statsTuple);
nullfrac2 = stats->stanullfrac;
mcv2_exists = get_attstatsslot(vardata2->statsTuple,
vardata2->atttype, vardata2->atttypmod,
mcv2_exists = get_attstatsslot(&mcv2_slot, vardata2->statsTuple,
STATISTIC_KIND_MCV, InvalidOid,
NULL,
&mcv2_values, &mcv2_nvalues,
&mcv2_numbers, &mcv2_nnumbers);
hist2_exists = get_attstatsslot(vardata2->statsTuple,
vardata2->atttype, vardata2->atttypmod,
ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS);
hist2_exists = get_attstatsslot(&hist2_slot, vardata2->statsTuple,
STATISTIC_KIND_HISTOGRAM, InvalidOid,
NULL,
&hist2_values, &hist2_nvalues,
NULL, NULL);
ATTSTATSSLOT_VALUES);
/* Arbitrarily limit number of MCVs considered */
mcv2_length = Min(mcv2_nvalues, MAX_CONSIDERED_ELEMS);
mcv2_length = Min(mcv2_slot.nvalues, MAX_CONSIDERED_ELEMS);
if (mcv2_exists)
sumcommon2 = mcv_population(mcv2_numbers, mcv2_length);
sumcommon2 = mcv_population(mcv2_slot.numbers, mcv2_length);
}
else
{
memset(&mcv2_slot, 0, sizeof(mcv2_slot));
memset(&hist2_slot, 0, sizeof(hist2_slot));
}
opr_codenum = inet_opr_codenum(operator);
@@ -499,10 +469,11 @@ networkjoinsel_semi(Oid operator,
{
for (i = 0; i < mcv1_length; i++)
{
selec += mcv1_numbers[i] *
inet_semi_join_sel(mcv1_values[i],
mcv2_exists, mcv2_values, mcv2_length,
hist2_exists, hist2_values, hist2_nvalues,
selec += mcv1_slot.numbers[i] *
inet_semi_join_sel(mcv1_slot.values[i],
mcv2_exists, mcv2_slot.values, mcv2_length,
hist2_exists,
hist2_slot.values, hist2_slot.nvalues,
hist2_weight,
&proc, opr_codenum);
}
@@ -519,21 +490,22 @@ networkjoinsel_semi(Oid operator,
*
* If there are too many histogram elements, decimate to limit runtime.
*/
if (hist1_exists && hist1_nvalues > 2 && (mcv2_exists || hist2_exists))
if (hist1_exists && hist1_slot.nvalues > 2 && (mcv2_exists || hist2_exists))
{
double hist_selec_sum = 0.0;
int k,
n;
k = (hist1_nvalues - 3) / MAX_CONSIDERED_ELEMS + 1;
k = (hist1_slot.nvalues - 3) / MAX_CONSIDERED_ELEMS + 1;
n = 0;
for (i = 1; i < hist1_nvalues - 1; i += k)
for (i = 1; i < hist1_slot.nvalues - 1; i += k)
{
hist_selec_sum +=
inet_semi_join_sel(hist1_values[i],
mcv2_exists, mcv2_values, mcv2_length,
hist2_exists, hist2_values, hist2_nvalues,
inet_semi_join_sel(hist1_slot.values[i],
mcv2_exists, mcv2_slot.values, mcv2_length,
hist2_exists,
hist2_slot.values, hist2_slot.nvalues,
hist2_weight,
&proc, opr_codenum);
n++;
@@ -550,18 +522,10 @@ networkjoinsel_semi(Oid operator,
selec = (1.0 - nullfrac1) * (1.0 - nullfrac2) * DEFAULT_SEL(operator);
/* Release stats. */
if (mcv1_exists)
free_attstatsslot(vardata1->atttype, mcv1_values, mcv1_nvalues,
mcv1_numbers, mcv1_nnumbers);
if (mcv2_exists)
free_attstatsslot(vardata2->atttype, mcv2_values, mcv2_nvalues,
mcv2_numbers, mcv2_nnumbers);
if (hist1_exists)
free_attstatsslot(vardata1->atttype, hist1_values, hist1_nvalues,
NULL, 0);
if (hist2_exists)
free_attstatsslot(vardata2->atttype, hist2_values, hist2_nvalues,
NULL, 0);
free_attstatsslot(&mcv1_slot);
free_attstatsslot(&mcv2_slot);
free_attstatsslot(&hist1_slot);
free_attstatsslot(&hist2_slot);
return selec;
}