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authorDavid Rowley2021-11-24 10:29:14 +0000
committerDavid Rowley2021-11-24 10:29:14 +0000
commit411137a429210e432f923264a8e313a9872910ca (patch)
tree2f635992ec138d1c68dbc38f77a6bcf3779a3fbd
parentfb5961fd13b1262df280e400645bdf4ed192f058 (diff)
Flush Memoize cache when non-key parameters change, take 2
It's possible that a subplan below a Memoize node contains a parameter from above the Memoize node. If this parameter changes then cache entries may become out-dated due to the new parameter value. Previously Memoize was mistakenly not aware of this. We fix this here by flushing the cache whenever a parameter that's not part of the cache key changes. Bug: #17213 Reported by: Elvis Pranskevichus Author: David Rowley Discussion: https://postgr.es/m/[email protected] Backpatch-through: 14, where Memoize was added
-rw-r--r--src/backend/executor/nodeMemoize.c38
-rw-r--r--src/backend/nodes/bitmapset.c2
-rw-r--r--src/backend/nodes/copyfuncs.c1
-rw-r--r--src/backend/nodes/outfuncs.c1
-rw-r--r--src/backend/nodes/readfuncs.c1
-rw-r--r--src/backend/optimizer/plan/createplan.c10
-rw-r--r--src/backend/optimizer/util/clauses.c31
-rw-r--r--src/include/nodes/execnodes.h2
-rw-r--r--src/include/nodes/plannodes.h1
-rw-r--r--src/include/optimizer/clauses.h2
-rw-r--r--src/test/regress/expected/memoize.out39
-rw-r--r--src/test/regress/sql/memoize.sql20
12 files changed, 145 insertions, 3 deletions
diff --git a/src/backend/executor/nodeMemoize.c b/src/backend/executor/nodeMemoize.c
index 683502dd90..31e3972223 100644
--- a/src/backend/executor/nodeMemoize.c
+++ b/src/backend/executor/nodeMemoize.c
@@ -368,6 +368,37 @@ remove_cache_entry(MemoizeState *mstate, MemoizeEntry *entry)
}
/*
+ * cache_purge_all
+ * Remove all items from the cache
+ */
+static void
+cache_purge_all(MemoizeState *mstate)
+{
+ uint64 evictions = mstate->hashtable->members;
+ PlanState *pstate = (PlanState *) mstate;
+
+ /*
+ * Likely the most efficient way to remove all items is to just reset the
+ * memory context for the cache and then rebuild a fresh hash table. This
+ * saves having to remove each item one by one and pfree each cached tuple
+ */
+ MemoryContextReset(mstate->tableContext);
+
+ /* Make the hash table the same size as the original size */
+ build_hash_table(mstate, ((Memoize *) pstate->plan)->est_entries);
+
+ /* reset the LRU list */
+ dlist_init(&mstate->lru_list);
+ mstate->last_tuple = NULL;
+ mstate->entry = NULL;
+
+ mstate->mem_used = 0;
+
+ /* XXX should we add something new to track these purges? */
+ mstate->stats.cache_evictions += evictions; /* Update Stats */
+}
+
+/*
* cache_reduce_memory
* Evict older and less recently used items from the cache in order to
* reduce the memory consumption back to something below the
@@ -979,6 +1010,7 @@ ExecInitMemoize(Memoize *node, EState *estate, int eflags)
* getting the first tuple. This allows us to mark it as so.
*/
mstate->singlerow = node->singlerow;
+ mstate->keyparamids = node->keyparamids;
/*
* Record if the cache keys should be compared bit by bit, or logically
@@ -1082,6 +1114,12 @@ ExecReScanMemoize(MemoizeState *node)
if (outerPlan->chgParam == NULL)
ExecReScan(outerPlan);
+ /*
+ * Purge the entire cache if a parameter changed that is not part of the
+ * cache key.
+ */
+ if (bms_nonempty_difference(outerPlan->chgParam, node->keyparamids))
+ cache_purge_all(node);
}
/*
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index 649478b0d4..bff70cfb1a 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -540,6 +540,8 @@ bms_overlap_list(const Bitmapset *a, const List *b)
/*
* bms_nonempty_difference - do sets have a nonempty difference?
+ *
+ * i.e., are any members set in 'a' that are not also set in 'b'.
*/
bool
bms_nonempty_difference(const Bitmapset *a, const Bitmapset *b)
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 7d55fd69ab..297b6ee715 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -973,6 +973,7 @@ _copyMemoize(const Memoize *from)
COPY_SCALAR_FIELD(singlerow);
COPY_SCALAR_FIELD(binary_mode);
COPY_SCALAR_FIELD(est_entries);
+ COPY_BITMAPSET_FIELD(keyparamids);
return newnode;
}
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index be374a0d70..3600c9fa36 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -868,6 +868,7 @@ _outMemoize(StringInfo str, const Memoize *node)
WRITE_BOOL_FIELD(singlerow);
WRITE_BOOL_FIELD(binary_mode);
WRITE_UINT_FIELD(est_entries);
+ WRITE_BITMAPSET_FIELD(keyparamids);
}
static void
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index a82c53ec0d..dcec3b728f 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -2232,6 +2232,7 @@ _readMemoize(void)
READ_BOOL_FIELD(singlerow);
READ_BOOL_FIELD(binary_mode);
READ_UINT_FIELD(est_entries);
+ READ_BITMAPSET_FIELD(keyparamids);
READ_DONE();
}
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 866f19f64c..f12660a260 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -280,7 +280,7 @@ static Material *make_material(Plan *lefttree);
static Memoize *make_memoize(Plan *lefttree, Oid *hashoperators,
Oid *collations, List *param_exprs,
bool singlerow, bool binary_mode,
- uint32 est_entries);
+ uint32 est_entries, Bitmapset *keyparamids);
static WindowAgg *make_windowagg(List *tlist, Index winref,
int partNumCols, AttrNumber *partColIdx, Oid *partOperators, Oid *partCollations,
int ordNumCols, AttrNumber *ordColIdx, Oid *ordOperators, Oid *ordCollations,
@@ -1586,6 +1586,7 @@ static Memoize *
create_memoize_plan(PlannerInfo *root, MemoizePath *best_path, int flags)
{
Memoize *plan;
+ Bitmapset *keyparamids;
Plan *subplan;
Oid *operators;
Oid *collations;
@@ -1617,9 +1618,11 @@ create_memoize_plan(PlannerInfo *root, MemoizePath *best_path, int flags)
i++;
}
+ keyparamids = pull_paramids((Expr *) param_exprs);
+
plan = make_memoize(subplan, operators, collations, param_exprs,
best_path->singlerow, best_path->binary_mode,
- best_path->est_entries);
+ best_path->est_entries, keyparamids);
copy_generic_path_info(&plan->plan, (Path *) best_path);
@@ -6420,7 +6423,7 @@ materialize_finished_plan(Plan *subplan)
static Memoize *
make_memoize(Plan *lefttree, Oid *hashoperators, Oid *collations,
List *param_exprs, bool singlerow, bool binary_mode,
- uint32 est_entries)
+ uint32 est_entries, Bitmapset *keyparamids)
{
Memoize *node = makeNode(Memoize);
Plan *plan = &node->plan;
@@ -6437,6 +6440,7 @@ make_memoize(Plan *lefttree, Oid *hashoperators, Oid *collations,
node->singlerow = singlerow;
node->binary_mode = binary_mode;
node->est_entries = est_entries;
+ node->keyparamids = keyparamids;
return node;
}
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 109f93d109..873e43bfe6 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -152,6 +152,7 @@ static Query *substitute_actual_srf_parameters(Query *expr,
int nargs, List *args);
static Node *substitute_actual_srf_parameters_mutator(Node *node,
substitute_actual_srf_parameters_context *context);
+static bool pull_paramids_walker(Node *node, Bitmapset **context);
/*****************************************************************************
@@ -5214,3 +5215,33 @@ substitute_actual_srf_parameters_mutator(Node *node,
substitute_actual_srf_parameters_mutator,
(void *) context);
}
+
+/*
+ * pull_paramids
+ * Returns a Bitmapset containing the paramids of all Params in 'expr'.
+ */
+Bitmapset *
+pull_paramids(Expr *expr)
+{
+ Bitmapset *result = NULL;
+
+ (void) pull_paramids_walker((Node *) expr, &result);
+
+ return result;
+}
+
+static bool
+pull_paramids_walker(Node *node, Bitmapset **context)
+{
+ if (node == NULL)
+ return false;
+ if (IsA(node, Param))
+ {
+ Param *param = (Param *)node;
+
+ *context = bms_add_member(*context, param->paramid);
+ return false;
+ }
+ return expression_tree_walker(node, pull_paramids_walker,
+ (void *) context);
+}
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index d96ace32e4..ddc3529332 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -2113,6 +2113,8 @@ typedef struct MemoizeState
* by bit, false when using hash equality ops */
MemoizeInstrumentation stats; /* execution statistics */
SharedMemoizeInfo *shared_info; /* statistics for parallel workers */
+ Bitmapset *keyparamids; /* Param->paramids of expressions belonging to
+ * param_exprs */
} MemoizeState;
/* ----------------
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index f1328be354..be3c30704a 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -804,6 +804,7 @@ typedef struct Memoize
uint32 est_entries; /* The maximum number of entries that the
* planner expects will fit in the cache, or 0
* if unknown */
+ Bitmapset *keyparamids; /* paramids from param_exprs */
} Memoize;
/* ----------------
diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h
index 0673887a85..bc3f3e60d4 100644
--- a/src/include/optimizer/clauses.h
+++ b/src/include/optimizer/clauses.h
@@ -53,4 +53,6 @@ extern void CommuteOpExpr(OpExpr *clause);
extern Query *inline_set_returning_function(PlannerInfo *root,
RangeTblEntry *rte);
+extern Bitmapset *pull_paramids(Expr *expr);
+
#endif /* CLAUSES_H */
diff --git a/src/test/regress/expected/memoize.out b/src/test/regress/expected/memoize.out
index 0ed5d8474a..4ca0bd1f1e 100644
--- a/src/test/regress/expected/memoize.out
+++ b/src/test/regress/expected/memoize.out
@@ -196,6 +196,45 @@ SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
(8 rows)
DROP TABLE strtest;
+-- Exercise Memoize code that flushes the cache when a parameter changes which
+-- is not part of the cache key.
+-- Ensure we get a Memoize plan
+EXPLAIN (COSTS OFF)
+SELECT unique1 FROM tenk1 t0
+WHERE unique1 < 3
+ AND EXISTS (
+ SELECT 1 FROM tenk1 t1
+ INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
+ WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
+ QUERY PLAN
+----------------------------------------------------------------
+ Index Scan using tenk1_unique1 on tenk1 t0
+ Index Cond: (unique1 < 3)
+ Filter: (SubPlan 1)
+ SubPlan 1
+ -> Nested Loop
+ -> Index Scan using tenk1_hundred on tenk1 t2
+ Filter: (t0.two <> four)
+ -> Memoize
+ Cache Key: t2.hundred
+ Cache Mode: logical
+ -> Index Scan using tenk1_unique1 on tenk1 t1
+ Index Cond: (unique1 = t2.hundred)
+ Filter: (t0.ten = twenty)
+(13 rows)
+
+-- Ensure the above query returns the correct result
+SELECT unique1 FROM tenk1 t0
+WHERE unique1 < 3
+ AND EXISTS (
+ SELECT 1 FROM tenk1 t1
+ INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
+ WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
+ unique1
+---------
+ 2
+(1 row)
+
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;
diff --git a/src/test/regress/sql/memoize.sql b/src/test/regress/sql/memoize.sql
index 3c7360adf9..c6ed5a2aa6 100644
--- a/src/test/regress/sql/memoize.sql
+++ b/src/test/regress/sql/memoize.sql
@@ -103,6 +103,26 @@ SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
DROP TABLE strtest;
+-- Exercise Memoize code that flushes the cache when a parameter changes which
+-- is not part of the cache key.
+
+-- Ensure we get a Memoize plan
+EXPLAIN (COSTS OFF)
+SELECT unique1 FROM tenk1 t0
+WHERE unique1 < 3
+ AND EXISTS (
+ SELECT 1 FROM tenk1 t1
+ INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
+ WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
+
+-- Ensure the above query returns the correct result
+SELECT unique1 FROM tenk1 t0
+WHERE unique1 < 3
+ AND EXISTS (
+ SELECT 1 FROM tenk1 t1
+ INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
+ WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
+
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;