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Allow Memoize to operate in binary comparison mode 

Memoize would always use the hash equality operator for the cache key
types to determine if the current set of parameters were the same as some
previously cached set.  Certain types such as floating points where -0.0
and +0.0 differ in their binary representation but are classed as equal by
the hash equality operator may cause problems as unless the join uses the
same operator it's possible that whichever join operator is being used
would be able to distinguish the two values.  In which case we may
accidentally return in the incorrect rows out of the cache.

To fix this here we add a binary mode to Memoize to allow it to the
current set of parameters to previously cached values by comparing
bit-by-bit rather than logically using the hash equality operator.  This
binary mode is always used for LATERAL joins and it's used for normal
joins when any of the join operators are not hashable.

Reported-by: Tom Lane
Author: David Rowley
Discussion: https://postgr.es/m/3004308.1632952496@sss.pgh.pa.us
Backpatch-through: 14, where Memoize was added
This commit is contained in:
David Rowley 2021-11-24 10:06:59 +13:00
parent 1922d7c6e1
commit e502150f7d
19 changed files with 346 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
contrib/postgres_fdw/expected/postgres_fdw.out
View File

@ -2247,6 +2247,7 @@ SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM
Output: t1."C 1", t1.c2, t1.c3, t1.c4, t1.c5, t1.c6, t1.c7, t1.c8
-> Memoize
Cache Key: t1.c2
Cache Mode: binary
-> Subquery Scan on q
-> HashAggregate
Output: t2.c1, t3.c1
@ -2255,7 +2256,7 @@ SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM
Output: t2.c1, t3.c1
Relations: (public.ft1 t2) INNER JOIN (public.ft2 t3)
Remote SQL: SELECT r1."C 1", r2."C 1" FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1")) AND ((r1.c2 = $1::integer))))
(16 rows)
(17 rows)
SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM ft1 t2, ft2 t3 WHERE t2.c1 = t3.c1 AND t2.c2 = t1.c2) q ORDER BY t1."C 1" OFFSET 10 LIMIT 10;
C 1

3
src/backend/commands/explain.c
View File

@ -3127,11 +3127,14 @@ show_memoize_info(MemoizeState *mstate, List *ancestors, ExplainState *es)
if (es->format != EXPLAIN_FORMAT_TEXT)
{
ExplainPropertyText("Cache Key", keystr.data, es);
ExplainPropertyText("Cache Mode", mstate->binary_mode ? "binary" : "logical", es);
}
else
{
ExplainIndentText(es);
appendStringInfo(es->str, "Cache Key: %s\n", keystr.data);
ExplainIndentText(es);
appendStringInfo(es->str, "Cache Mode: %s\n", mstate->binary_mode ? "binary" : "logical");
}
pfree(keystr.data);

94
src/backend/executor/nodeMemoize.c
View File

@ -71,6 +71,7 @@
#include "executor/nodeMemoize.h"
#include "lib/ilist.h"
#include "miscadmin.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
/* States of the ExecMemoize state machine */
@ -131,7 +132,7 @@ typedef struct MemoizeEntry
static uint32 MemoizeHash_hash(struct memoize_hash *tb,
const MemoizeKey *key);
static int MemoizeHash_equal(struct memoize_hash *tb,
static bool MemoizeHash_equal(struct memoize_hash *tb,
const MemoizeKey *params1,
const MemoizeKey *params2);
@ -140,7 +141,7 @@ static int MemoizeHash_equal(struct memoize_hash *tb,
#define SH_KEY_TYPE MemoizeKey *
#define SH_KEY key
#define SH_HASH_KEY(tb, key) MemoizeHash_hash(tb, key)
#define SH_EQUAL(tb, a, b) (MemoizeHash_equal(tb, a, b) == 0)
#define SH_EQUAL(tb, a, b) MemoizeHash_equal(tb, a, b)
#define SH_SCOPE static inline
#define SH_STORE_HASH
#define SH_GET_HASH(tb, a) a->hash
@ -160,21 +161,45 @@ MemoizeHash_hash(struct memoize_hash *tb, const MemoizeKey *key)
TupleTableSlot *pslot = mstate->probeslot;
uint32 hashkey = 0;
int numkeys = mstate->nkeys;
FmgrInfo *hashfunctions = mstate->hashfunctions;
Oid *collations = mstate->collations;
for (int i = 0; i < numkeys; i++)
if (mstate->binary_mode)
{
/* rotate hashkey left 1 bit at each step */
hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
if (!pslot->tts_isnull[i]) /* treat nulls as having hash key 0 */
for (int i = 0; i < numkeys; i++)
{
uint32 hkey;
/* rotate hashkey left 1 bit at each step */
hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
hkey = DatumGetUInt32(FunctionCall1Coll(&hashfunctions[i],
collations[i], pslot->tts_values[i]));
hashkey ^= hkey;
if (!pslot->tts_isnull[i]) /* treat nulls as having hash key 0 */
{
FormData_pg_attribute *attr;
uint32 hkey;
attr = &pslot->tts_tupleDescriptor->attrs[i];
hkey = datum_image_hash(pslot->tts_values[i], attr->attbyval, attr->attlen);
hashkey ^= hkey;
}
}
}
else
{
FmgrInfo *hashfunctions = mstate->hashfunctions;
Oid *collations = mstate->collations;
for (int i = 0; i < numkeys; i++)
{
/* rotate hashkey left 1 bit at each step */
hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
if (!pslot->tts_isnull[i]) /* treat nulls as having hash key 0 */
{
uint32 hkey;
hkey = DatumGetUInt32(FunctionCall1Coll(&hashfunctions[i],
collations[i], pslot->tts_values[i]));
hashkey ^= hkey;
}
}
}
@ -187,7 +212,7 @@ MemoizeHash_hash(struct memoize_hash *tb, const MemoizeKey *key)
* table lookup. 'key2' is never used. Instead the MemoizeState's
* probeslot is always populated with details of what's being looked up.
*/
static int
static bool
MemoizeHash_equal(struct memoize_hash *tb, const MemoizeKey *key1,
const MemoizeKey *key2)
{
@ -199,9 +224,38 @@ MemoizeHash_equal(struct memoize_hash *tb, const MemoizeKey *key1,
/* probeslot should have already been prepared by prepare_probe_slot() */
ExecStoreMinimalTuple(key1->params, tslot, false);
econtext->ecxt_innertuple = tslot;
econtext->ecxt_outertuple = pslot;
return !ExecQualAndReset(mstate->cache_eq_expr, econtext);
if (mstate->binary_mode)
{
int numkeys = mstate->nkeys;
slot_getallattrs(tslot);
slot_getallattrs(pslot);
for (int i = 0; i < numkeys; i++)
{
FormData_pg_attribute *attr;
if (tslot->tts_isnull[i] != pslot->tts_isnull[i])
return false;
/* both NULL? they're equal */
if (tslot->tts_isnull[i])
continue;
/* perform binary comparison on the two datums */
attr = &tslot->tts_tupleDescriptor->attrs[i];
if (!datum_image_eq(tslot->tts_values[i], pslot->tts_values[i],
attr->attbyval, attr->attlen))
return false;
}
return true;
}
else
{
econtext->ecxt_innertuple = tslot;
econtext->ecxt_outertuple = pslot;
return ExecQualAndReset(mstate->cache_eq_expr, econtext);
}
}
/*
@ -926,6 +980,12 @@ ExecInitMemoize(Memoize *node, EState *estate, int eflags)
*/
mstate->singlerow = node->singlerow;
/*
* Record if the cache keys should be compared bit by bit, or logically
* using the type's hash equality operator
*/
mstate->binary_mode = node->binary_mode;
/* Zero the statistics counters */
memset(&mstate->stats, 0, sizeof(MemoizeInstrumentation));

1
src/backend/nodes/copyfuncs.c
View File

@ -971,6 +971,7 @@ _copyMemoize(const Memoize *from)
COPY_POINTER_FIELD(collations, sizeof(Oid) * from->numKeys);
COPY_NODE_FIELD(param_exprs);
COPY_SCALAR_FIELD(singlerow);
COPY_SCALAR_FIELD(binary_mode);
COPY_SCALAR_FIELD(est_entries);
return newnode;

2
src/backend/nodes/outfuncs.c
View File

@ -866,6 +866,7 @@ _outMemoize(StringInfo str, const Memoize *node)
WRITE_OID_ARRAY(collations, node->numKeys);
WRITE_NODE_FIELD(param_exprs);
WRITE_BOOL_FIELD(singlerow);
WRITE_BOOL_FIELD(binary_mode);
WRITE_UINT_FIELD(est_entries);
}
@ -1966,6 +1967,7 @@ _outMemoizePath(StringInfo str, const MemoizePath *node)
WRITE_NODE_FIELD(hash_operators);
WRITE_NODE_FIELD(param_exprs);
WRITE_BOOL_FIELD(singlerow);
WRITE_BOOL_FIELD(binary_mode);
WRITE_FLOAT_FIELD(calls, "%.0f");
WRITE_UINT_FIELD(est_entries);
}

1
src/backend/nodes/readfuncs.c
View File

@ -2230,6 +2230,7 @@ _readMemoize(void)
READ_OID_ARRAY(collations, local_node->numKeys);
READ_NODE_FIELD(param_exprs);
READ_BOOL_FIELD(singlerow);
READ_BOOL_FIELD(binary_mode);
READ_UINT_FIELD(est_entries);
READ_DONE();

38
src/backend/optimizer/path/joinpath.c
View File

@ -371,19 +371,21 @@ allow_star_schema_join(PlannerInfo *root,
* Returns true the hashing is possible, otherwise return false.
*
* Additionally we also collect the outer exprs and the hash operators for
* each parameter to innerrel. These set in 'param_exprs' and 'operators'
* when we return true.
* each parameter to innerrel. These set in 'param_exprs', 'operators' and
* 'binary_mode' when we return true.
*/
static bool
paraminfo_get_equal_hashops(PlannerInfo *root, ParamPathInfo *param_info,
RelOptInfo *outerrel, RelOptInfo *innerrel,
List **param_exprs, List **operators)
List **param_exprs, List **operators,
bool *binary_mode)
{
ListCell *lc;
*param_exprs = NIL;
*operators = NIL;
*binary_mode = false;
if (param_info != NULL)
{
@ -431,6 +433,20 @@ paraminfo_get_equal_hashops(PlannerInfo *root, ParamPathInfo *param_info,
*operators = lappend_oid(*operators, hasheqoperator);
*param_exprs = lappend(*param_exprs, expr);
/*
* When the join operator is not hashable then it's possible that
* the operator will be able to distinguish something that the
* hash equality operator could not. For example with floating
* point types -0.0 and +0.0 are classed as equal by the hash
* function and equality function, but some other operator may be
* able to tell those values apart. This means that we must put
* memoize into binary comparison mode so that it does bit-by-bit
* comparisons rather than a "logical" comparison as it would
* using the hash equality operator.
*/
if (!OidIsValid(rinfo->hashjoinoperator))
*binary_mode = true;
}
}
@ -461,6 +477,17 @@ paraminfo_get_equal_hashops(PlannerInfo *root, ParamPathInfo *param_info,
*operators = lappend_oid(*operators, typentry->eq_opr);
*param_exprs = lappend(*param_exprs, expr);
/*
* We must go into binary mode as we don't have too much of an idea of
* how these lateral Vars are being used. See comment above when we
* set *binary_mode for the non-lateral Var case. This could be
* relaxed a bit if we had the RestrictInfos and knew the operators
* being used, however for cases like Vars that are arguments to
* functions we must operate in binary mode as we don't have
* visibility into what the function is doing with the Vars.
*/
*binary_mode = true;
}
/* We're okay to use memoize */
@ -481,6 +508,7 @@ get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
List *param_exprs;
List *hash_operators;
ListCell *lc;
bool binary_mode;
/* Obviously not if it's disabled */
if (!enable_memoize)
@ -572,7 +600,8 @@ get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
outerrel,
innerrel,
&param_exprs,
&hash_operators))
&hash_operators,
&binary_mode))
{
return (Path *) create_memoize_path(root,
innerrel,
@ -580,6 +609,7 @@ get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
param_exprs,
hash_operators,
extra->inner_unique,
binary_mode,
outer_path->parent->rows);
}

10
src/backend/optimizer/plan/createplan.c
View File

@ -279,7 +279,8 @@ static Sort *make_sort_from_groupcols(List *groupcls,
static Material *make_material(Plan *lefttree);
static Memoize *make_memoize(Plan *lefttree, Oid *hashoperators,
Oid *collations, List *param_exprs,
bool singlerow, uint32 est_entries);
bool singlerow, bool binary_mode,
uint32 est_entries);
static WindowAgg *make_windowagg(List *tlist, Index winref,
int partNumCols, AttrNumber *partColIdx, Oid *partOperators, Oid *partCollations,
int ordNumCols, AttrNumber *ordColIdx, Oid *ordOperators, Oid *ordCollations,
@ -1617,7 +1618,8 @@ create_memoize_plan(PlannerInfo *root, MemoizePath *best_path, int flags)
}
plan = make_memoize(subplan, operators, collations, param_exprs,
best_path->singlerow, best_path->est_entries);
best_path->singlerow, best_path->binary_mode,
best_path->est_entries);
copy_generic_path_info(&plan->plan, (Path *) best_path);
@ -6417,7 +6419,8 @@ materialize_finished_plan(Plan *subplan)
static Memoize *
make_memoize(Plan *lefttree, Oid *hashoperators, Oid *collations,
List *param_exprs, bool singlerow, uint32 est_entries)
List *param_exprs, bool singlerow, bool binary_mode,
uint32 est_entries)
{
Memoize *node = makeNode(Memoize);
Plan *plan = &node->plan;
@ -6432,6 +6435,7 @@ make_memoize(Plan *lefttree, Oid *hashoperators, Oid *collations,
node->collations = collations;
node->param_exprs = param_exprs;
node->singlerow = singlerow;
node->binary_mode = binary_mode;
node->est_entries = est_entries;
return node;

4
src/backend/optimizer/util/pathnode.c
View File

@ -1583,7 +1583,7 @@ create_material_path(RelOptInfo *rel, Path *subpath)
MemoizePath *
create_memoize_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
List *param_exprs, List *hash_operators,
bool singlerow, double calls)
bool singlerow, bool binary_mode, double calls)
{
MemoizePath *pathnode = makeNode(MemoizePath);
@ -1603,6 +1603,7 @@ create_memoize_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
pathnode->hash_operators = hash_operators;
pathnode->param_exprs = param_exprs;
pathnode->singlerow = singlerow;
pathnode->binary_mode = binary_mode;
pathnode->calls = calls;
/*
@ -3942,6 +3943,7 @@ reparameterize_path(PlannerInfo *root, Path *path,
mpath->param_exprs,
mpath->hash_operators,
mpath->singlerow,
mpath->binary_mode,
mpath->calls);
}
default:

52
src/backend/utils/adt/datum.c
View File

@ -43,6 +43,7 @@
#include "postgres.h"
#include "access/detoast.h"
#include "common/hashfn.h"
#include "fmgr.h"
#include "utils/builtins.h"
#include "utils/datum.h"
@ -324,6 +325,57 @@ datum_image_eq(Datum value1, Datum value2, bool typByVal, int typLen)
return result;
}
/*-------------------------------------------------------------------------
* datum_image_hash
*
* Generate a hash value based on the binary representation of 'value'. Most
* use cases will want to use the hash function specific to the Datum's type,
* however, some corner cases require generating a hash value based on the
* actual bits rather than the logical value.
*-------------------------------------------------------------------------
*/
uint32
datum_image_hash(Datum value, bool typByVal, int typLen)
{
Size len;
uint32 result;
if (typByVal)
result = hash_bytes((unsigned char *) &value, sizeof(Datum));
else if (typLen > 0)
result = hash_bytes((unsigned char *) DatumGetPointer(value), typLen);
else if (typLen == -1)
{
struct varlena *val;
len = toast_raw_datum_size(value);
val = PG_DETOAST_DATUM_PACKED(value);
result = hash_bytes((unsigned char *) VARDATA_ANY(val), len - VARHDRSZ);
/* Only free memory if it's a copy made here. */
if ((Pointer) val != (Pointer) value)
pfree(val);
}
else if (typLen == -2)
{
char *s;
s = DatumGetCString(value);
len = strlen(s) + 1;
result = hash_bytes((unsigned char *) s, len);
}
else
{
elog(ERROR, "unexpected typLen: %d", typLen);
result = 0; /* keep compiler quiet */
}
return result;
}
/*-------------------------------------------------------------------------
* btequalimage
*

2
src/include/nodes/execnodes.h
View File

@ -2109,6 +2109,8 @@ typedef struct MemoizeState
* NULL if 'last_tuple' is NULL. */
bool singlerow; /* true if the cache entry is to be marked as
* complete after caching the first tuple. */
bool binary_mode; /* true when cache key should be compared bit
* by bit, false when using hash equality ops */
MemoizeInstrumentation stats; /* execution statistics */
SharedMemoizeInfo *shared_info; /* statistics for parallel workers */
} MemoizeState;

2
src/include/nodes/pathnodes.h
View File

@ -1515,6 +1515,8 @@ typedef struct MemoizePath
List *param_exprs; /* cache keys */
bool singlerow; /* true if the cache entry is to be marked as
* complete after caching the first record. */
bool binary_mode; /* true when cache key should be compared bit
* by bit, false when using hash equality ops */
Cardinality calls; /* expected number of rescans */
uint32 est_entries; /* The maximum number of entries that the
* planner expects will fit in the cache, or 0

2
src/include/nodes/plannodes.h
View File

@ -799,6 +799,8 @@ typedef struct Memoize
bool singlerow; /* true if the cache entry should be marked as
* complete after we store the first tuple in
* it. */
bool binary_mode; /* true when cache key should be compared bit
* by bit, false when using hash equality ops */
uint32 est_entries; /* The maximum number of entries that the
* planner expects will fit in the cache, or 0
* if unknown */

1
src/include/optimizer/pathnode.h
View File

@ -88,6 +88,7 @@ extern MemoizePath *create_memoize_path(PlannerInfo *root,
List *param_exprs,
List *hash_operators,
bool singlerow,
bool binary_mode,
double calls);
extern UniquePath *create_unique_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath, SpecialJoinInfo *sjinfo);

8
src/include/utils/datum.h
View File

@ -55,6 +55,14 @@ extern bool datumIsEqual(Datum value1, Datum value2,
extern bool datum_image_eq(Datum value1, Datum value2,
bool typByVal, int typLen);
/*
* datum_image_hash
*
* Generates hash value for 'value' based on its bits rather than logical
* value.
*/
extern uint32 datum_image_hash(Datum value, bool typByVal, int typLen);
/*
* Serialize and restore datums so that we can transfer them to parallel
* workers.

28
src/test/regress/expected/join.out
View File

@ -3686,9 +3686,10 @@ where t1.unique1 = 1;
Index Cond: (hundred = t1.hundred)
-> Memoize
Cache Key: t2.thousand
Cache Mode: logical
-> Index Scan using tenk1_unique2 on tenk1 t3
Index Cond: (unique2 = t2.thousand)
(13 rows)
(14 rows)
explain (costs off)
select * from tenk1 t1 left join
@ -3708,9 +3709,10 @@ where t1.unique1 = 1;
Index Cond: (hundred = t1.hundred)
-> Memoize
Cache Key: t2.thousand
Cache Mode: logical
-> Index Scan using tenk1_unique2 on tenk1 t3
Index Cond: (unique2 = t2.thousand)
(13 rows)
(14 rows)
explain (costs off)
select count(*) from
@ -4238,11 +4240,12 @@ where t1.f1 = ss.f1;
-> Memoize
Output: (i8.q1), t2.f1
Cache Key: i8.q1
Cache Mode: binary
-> Limit
Output: (i8.q1), t2.f1
-> Seq Scan on public.text_tbl t2
Output: i8.q1, t2.f1
(19 rows)
(20 rows)
select * from
text_tbl t1
@ -4282,6 +4285,7 @@ where t1.f1 = ss2.f1;
-> Memoize
Output: (i8.q1), t2.f1
Cache Key: i8.q1
Cache Mode: binary
-> Limit
Output: (i8.q1), t2.f1
-> Seq Scan on public.text_tbl t2
@ -4289,11 +4293,12 @@ where t1.f1 = ss2.f1;
-> Memoize
Output: ((i8.q1)), (t2.f1)
Cache Key: (i8.q1), t2.f1
Cache Mode: binary
-> Limit
Output: ((i8.q1)), (t2.f1)
-> Seq Scan on public.text_tbl t3
Output: (i8.q1), t2.f1
(28 rows)
(30 rows)
select * from
text_tbl t1
@ -4342,6 +4347,7 @@ where tt1.f1 = ss1.c0;
-> Memoize
Output: ss1.c0
Cache Key: tt4.f1
Cache Mode: binary
-> Subquery Scan on ss1
Output: ss1.c0
Filter: (ss1.c0 = 'foo'::text)
@ -4349,7 +4355,7 @@ where tt1.f1 = ss1.c0;
Output: (tt4.f1)
-> Seq Scan on public.text_tbl tt5
Output: tt4.f1
(32 rows)
(33 rows)
select 1 from
text_tbl as tt1
@ -5058,8 +5064,9 @@ explain (costs off)
-> Seq Scan on tenk1 a
-> Memoize
Cache Key: a.two
Cache Mode: binary
-> Function Scan on generate_series g
(6 rows)
(7 rows)
explain (costs off)
select count(*) from tenk1 a cross join lateral generate_series(1,two) g;
@ -5070,8 +5077,9 @@ explain (costs off)
-> Seq Scan on tenk1 a
-> Memoize
Cache Key: a.two
Cache Mode: binary
-> Function Scan on generate_series g
(6 rows)
(7 rows)
-- don't need the explicit LATERAL keyword for functions
explain (costs off)
@ -5083,8 +5091,9 @@ explain (costs off)
-> Seq Scan on tenk1 a
-> Memoize
Cache Key: a.two
Cache Mode: binary
-> Function Scan on generate_series g
(6 rows)
(7 rows)
-- lateral with UNION ALL subselect
explain (costs off)
@ -5145,9 +5154,10 @@ explain (costs off)
-> Values Scan on "*VALUES*"
-> Memoize
Cache Key: "*VALUES*".column1
Cache Mode: logical
-> Index Only Scan using tenk1_unique2 on tenk1 b
Index Cond: (unique2 = "*VALUES*".column1)
(9 rows)
(10 rows)
select count(*) from tenk1 a,
tenk1 b join lateral (values(a.unique1),(-1)) ss(x) on b.unique2 = ss.x;

93
src/test/regress/expected/memoize.out
View File

@ -44,11 +44,12 @@ WHERE t2.unique1 < 1000;', false);
Rows Removed by Filter: 9000
-> Memoize (actual rows=1 loops=N)
Cache Key: t2.twenty
Cache Mode: logical
Hits: 980 Misses: 20 Evictions: Zero Overflows: 0 Memory Usage: NkB
-> Index Only Scan using tenk1_unique1 on tenk1 t1 (actual rows=1 loops=N)
Index Cond: (unique1 = t2.twenty)
Heap Fetches: N
(11 rows)
(12 rows)
-- And check we get the expected results.
SELECT COUNT(*),AVG(t1.unique1) FROM tenk1 t1
@ -73,11 +74,12 @@ WHERE t1.unique1 < 1000;', false);
Rows Removed by Filter: 9000
-> Memoize (actual rows=1 loops=N)
Cache Key: t1.twenty
Cache Mode: logical
Hits: 980 Misses: 20 Evictions: Zero Overflows: 0 Memory Usage: NkB
-> Index Only Scan using tenk1_unique1 on tenk1 t2 (actual rows=1 loops=N)
Index Cond: (unique1 = t1.twenty)
Heap Fetches: N
(11 rows)
(12 rows)
-- And check we get the expected results.
SELECT COUNT(*),AVG(t2.unique1) FROM tenk1 t1,
@ -107,12 +109,94 @@ WHERE t2.unique1 < 1200;', true);
Rows Removed by Filter: 8800
-> Memoize (actual rows=1 loops=N)
Cache Key: t2.thousand
Cache Mode: logical
Hits: N Misses: N Evictions: N Overflows: 0 Memory Usage: NkB
-> Index Only Scan using tenk1_unique1 on tenk1 t1 (actual rows=1 loops=N)
Index Cond: (unique1 = t2.thousand)
Heap Fetches: N
(11 rows)
(12 rows)
CREATE TABLE flt (f float);
CREATE INDEX flt_f_idx ON flt (f);
INSERT INTO flt VALUES('-0.0'::float),('+0.0'::float);
ANALYZE flt;
SET enable_seqscan TO off;
-- Ensure memoize operates in logical mode
SELECT explain_memoize('
SELECT * FROM flt f1 INNER JOIN flt f2 ON f1.f = f2.f;', false);
explain_memoize
-------------------------------------------------------------------------------
Nested Loop (actual rows=4 loops=N)
-> Index Only Scan using flt_f_idx on flt f1 (actual rows=2 loops=N)
Heap Fetches: N
-> Memoize (actual rows=2 loops=N)
Cache Key: f1.f
Cache Mode: logical
Hits: 1 Misses: 1 Evictions: Zero Overflows: 0 Memory Usage: NkB
-> Index Only Scan using flt_f_idx on flt f2 (actual rows=2 loops=N)
Index Cond: (f = f1.f)
Heap Fetches: N
(10 rows)
-- Ensure memoize operates in binary mode
SELECT explain_memoize('
SELECT * FROM flt f1 INNER JOIN flt f2 ON f1.f >= f2.f;', false);
explain_memoize
-------------------------------------------------------------------------------
Nested Loop (actual rows=4 loops=N)
-> Index Only Scan using flt_f_idx on flt f1 (actual rows=2 loops=N)
Heap Fetches: N
-> Memoize (actual rows=2 loops=N)
Cache Key: f1.f
Cache Mode: binary
Hits: 0 Misses: 2 Evictions: Zero Overflows: 0 Memory Usage: NkB
-> Index Only Scan using flt_f_idx on flt f2 (actual rows=2 loops=N)
Index Cond: (f <= f1.f)
Heap Fetches: N
(10 rows)
DROP TABLE flt;
-- Exercise Memoize in binary mode with a large fixed width type and a
-- varlena type.
CREATE TABLE strtest (n name, t text);
CREATE INDEX strtest_n_idx ON strtest (n);
CREATE INDEX strtest_t_idx ON strtest (t);
INSERT INTO strtest VALUES('one','one'),('two','two'),('three',repeat(md5('three'),100));
-- duplicate rows so we get some cache hits
INSERT INTO strtest SELECT * FROM strtest;
ANALYZE strtest;
-- Ensure we get 3 hits and 3 misses
SELECT explain_memoize('
SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.n >= s2.n;', false);
explain_memoize
----------------------------------------------------------------------------------
Nested Loop (actual rows=24 loops=N)
-> Seq Scan on strtest s1 (actual rows=6 loops=N)
-> Memoize (actual rows=4 loops=N)
Cache Key: s1.n
Cache Mode: binary
Hits: 3 Misses: 3 Evictions: Zero Overflows: 0 Memory Usage: NkB
-> Index Scan using strtest_n_idx on strtest s2 (actual rows=4 loops=N)
Index Cond: (n <= s1.n)
(8 rows)
-- Ensure we get 3 hits and 3 misses
SELECT explain_memoize('
SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
explain_memoize
----------------------------------------------------------------------------------
Nested Loop (actual rows=24 loops=N)
-> Seq Scan on strtest s1 (actual rows=6 loops=N)
-> Memoize (actual rows=4 loops=N)
Cache Key: s1.t
Cache Mode: binary
Hits: 3 Misses: 3 Evictions: Zero Overflows: 0 Memory Usage: NkB
-> Index Scan using strtest_t_idx on strtest s2 (actual rows=4 loops=N)
Index Cond: (t <= s1.t)
(8 rows)
DROP TABLE strtest;
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;
RESET enable_bitmapscan;
@ -140,9 +224,10 @@ WHERE t1.unique1 < 1000;
Index Cond: (unique1 < 1000)
-> Memoize
Cache Key: t1.twenty
Cache Mode: logical
-> Index Only Scan using tenk1_unique1 on tenk1 t2
Index Cond: (unique1 = t1.twenty)
(13 rows)
(14 rows)
-- And ensure the parallel plan gives us the correct results.
SELECT COUNT(*),AVG(t2.unique1) FROM tenk1 t1,

3
src/test/regress/expected/subselect.out
View File

@ -1139,13 +1139,14 @@ where o.ten = 1;
Filter: (ten = 1)
-> Memoize
Cache Key: o.four
Cache Mode: binary
-> CTE Scan on x
CTE x
-> Recursive Union
-> Result
-> WorkTable Scan on x x_1
Filter: (a < 10)
(12 rows)
(13 rows)
select sum(o.four), sum(ss.a) from
onek o cross join lateral (

39
src/test/regress/sql/memoize.sql
View File

@ -65,6 +65,45 @@ SELECT explain_memoize('
SELECT COUNT(*),AVG(t1.unique1) FROM tenk1 t1
INNER JOIN tenk1 t2 ON t1.unique1 = t2.thousand
WHERE t2.unique1 < 1200;', true);
CREATE TABLE flt (f float);
CREATE INDEX flt_f_idx ON flt (f);
INSERT INTO flt VALUES('-0.0'::float),('+0.0'::float);
ANALYZE flt;
SET enable_seqscan TO off;
-- Ensure memoize operates in logical mode
SELECT explain_memoize('
SELECT * FROM flt f1 INNER JOIN flt f2 ON f1.f = f2.f;', false);
-- Ensure memoize operates in binary mode
SELECT explain_memoize('
SELECT * FROM flt f1 INNER JOIN flt f2 ON f1.f >= f2.f;', false);
DROP TABLE flt;
-- Exercise Memoize in binary mode with a large fixed width type and a
-- varlena type.
CREATE TABLE strtest (n name, t text);
CREATE INDEX strtest_n_idx ON strtest (n);
CREATE INDEX strtest_t_idx ON strtest (t);
INSERT INTO strtest VALUES('one','one'),('two','two'),('three',repeat(md5('three'),100));
-- duplicate rows so we get some cache hits
INSERT INTO strtest SELECT * FROM strtest;
ANALYZE strtest;
-- Ensure we get 3 hits and 3 misses
SELECT explain_memoize('
SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.n >= s2.n;', false);
-- Ensure we get 3 hits and 3 misses
SELECT explain_memoize('
SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
DROP TABLE strtest;
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;
RESET enable_bitmapscan;