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Commit4e23236

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Improve commentary about run-time partition pruning data structures.
No code changes except for a couple of new Asserts.David Rowley and Tom LaneDiscussion:https://postgr.es/m/CAKJS1f-6GODRNgEtdPxCnAPme2h2hTztB6LmtfdmcYAAOE0kQg@mail.gmail.com
1 parente5d11b9 commit4e23236

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5 files changed

+71
-45
lines changed

5 files changed

+71
-45
lines changed

‎src/backend/optimizer/path/allpaths.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1451,7 +1451,8 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
14511451

14521452
/*
14531453
* If we need to build partitioned_rels, accumulate the partitioned
1454-
* rels for this child.
1454+
* rels for this child. We must ensure that parents are always listed
1455+
* before their child partitioned tables.
14551456
*/
14561457
if (build_partitioned_rels)
14571458
{

‎src/backend/partitioning/partprune.c

Lines changed: 24 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -202,12 +202,17 @@ make_partition_pruneinfo(PlannerInfo *root, List *partition_rels,
202202
inti;
203203

204204
/*
205-
* Allocate two arrays to store the 1-based indexes of the 'subpaths' and
206-
* 'partitioned_rels' by relid.
205+
* Construct two temporary arrays to map from planner relids to subplan
206+
* and sub-partition indexes. For convenience, we use 1-based indexes
207+
* here, so that zero can represent an un-filled array entry.
207208
*/
208209
relid_subplan_map=palloc0(sizeof(int)*root->simple_rel_array_size);
209210
relid_subpart_map=palloc0(sizeof(int)*root->simple_rel_array_size);
210211

212+
/*
213+
* relid_subplan_map maps relid of a leaf partition to the index in
214+
* 'subpaths' of the scan plan for that partition.
215+
*/
211216
i=1;
212217
foreach(lc,subpaths)
213218
{
@@ -216,17 +221,27 @@ make_partition_pruneinfo(PlannerInfo *root, List *partition_rels,
216221

217222
Assert(IS_SIMPLE_REL(pathrel));
218223
Assert(pathrel->relid<root->simple_rel_array_size);
224+
/* No duplicates please */
225+
Assert(relid_subplan_map[pathrel->relid]==0);
219226

220227
relid_subplan_map[pathrel->relid]=i++;
221228
}
222229

223-
/* Likewise for the partition_rels */
230+
/*
231+
* relid_subpart_map maps relid of a non-leaf partition to the index in
232+
* 'partition_rels' of that rel (which will also be the index in the
233+
* returned PartitionPruneInfo list of the info for that partition).
234+
*/
224235
i=1;
225236
foreach(lc,partition_rels)
226237
{
227238
Indexrti=lfirst_int(lc);
228239

229240
Assert(rti<root->simple_rel_array_size);
241+
/* No duplicates please */
242+
Assert(relid_subpart_map[rti]==0);
243+
/* Same rel cannot be both leaf and non-leaf */
244+
Assert(relid_subplan_map[rti]==0);
230245

231246
relid_subpart_map[rti]=i++;
232247
}
@@ -287,16 +302,16 @@ make_partition_pruneinfo(PlannerInfo *root, List *partition_rels,
287302
returnNIL;
288303
}
289304

305+
/*
306+
* Construct the subplan and subpart maps for this partitioning level.
307+
* Here we convert to zero-based indexes, with -1 for empty entries.
308+
* Also construct a Bitmapset of all partitions that are present (that
309+
* is, not pruned already).
310+
*/
290311
subplan_map= (int*)palloc(nparts*sizeof(int));
291312
subpart_map= (int*)palloc(nparts*sizeof(int));
292313
present_parts=NULL;
293314

294-
/*
295-
* Loop over each partition of the partitioned rel and record the
296-
* subpath index for each. Any partitions which are not present in
297-
* the subpaths List will be set to -1, and any sub-partitioned table
298-
* which is not present will also be set to -1.
299-
*/
300315
for (i=0;i<nparts;i++)
301316
{
302317
RelOptInfo*partrel=subpart->part_rels[i];
@@ -305,12 +320,6 @@ make_partition_pruneinfo(PlannerInfo *root, List *partition_rels,
305320

306321
subplan_map[i]=subplanidx;
307322
subpart_map[i]=subpartidx;
308-
309-
/*
310-
* Record the indexes of all the partition indexes that we have
311-
* subplans or subparts for. This allows an optimization to skip
312-
* attempting any run-time pruning when it's irrelevant.
313-
*/
314323
if (subplanidx >=0||subpartidx >=0)
315324
present_parts=bms_add_member(present_parts,i);
316325
}

‎src/include/executor/execPartition.h

Lines changed: 21 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -113,30 +113,27 @@ typedef struct PartitionTupleRouting
113113
}PartitionTupleRouting;
114114

115115
/*-----------------------
116-
* PartitionPruningData - Encapsulates all information required to support
117-
* elimination of partitions in plan types which support arbitrary Lists of
118-
* subplans. Information stored here allows the partition pruning functions
119-
* to be called and the return value of partition indexes translated into the
120-
* subpath indexes of plan types such as Append, thus allowing us to bypass a
121-
* subplan when we can prove that no tuple matching the 'pruning_steps' will
122-
* be found within.
116+
* PartitionPruningData - Per-partitioned-table data for run-time pruning
117+
* of partitions. For a multilevel partitioned table, we have one of these
118+
* for the topmost partition plus one for each non-leaf child partition,
119+
* ordered such that parents appear before their children.
123120
*
124-
* subplan_mapAn array containingthesubplan index which
125-
*matches this partition index, or -1 if the
126-
*subplan has been pruned already.
127-
* subpart_mapAn array containing the index into the
128-
*partprunedata array in PartitionPruneState, or
129-
*-1 if there is no such element in that array.
121+
* subplan_map[] and subpart_map[] havethesame definitions as in
122+
* PartitionPruneInfo (see plannodes.h); though note that here,
123+
* subpart_map contains indexes into PartitionPruneState.partprunedata[].
124+
*
125+
* subplan_mapSubplan index by partition index, or -1.
126+
* subpart_mapSubpart index by partition index, or -1.
130127
* present_partsA Bitmapset of the partition indexes that we
131-
*have subplansmapped for.
128+
*have subplansor subparts for.
132129
* contextContains the context details required to call
133130
*the partition pruning code.
134131
* pruning_stepsList of PartitionPruneSteps used to
135132
*perform the actual pruning.
136133
* do_initial_prunetrue if pruning should be performed during
137-
*executor startup.
134+
*executor startup (for this partitioning level).
138135
* do_exec_prunetrue if pruning should be performed during
139-
*executor run.
136+
*executor run (for this partitioning level).
140137
*-----------------------
141138
*/
142139
typedefstructPartitionPruningData
@@ -152,16 +149,18 @@ typedef struct PartitionPruningData
152149

153150
/*-----------------------
154151
* PartitionPruneState - State object required for plan nodes to perform
155-
* partition pruning elimination of their subplans. This encapsulates a
156-
* flattened hierarchy of PartitionPruningData structs.
152+
*run-timepartition pruning.
153+
*
157154
* This struct can be attached to plan types which support arbitrary Lists of
158155
* subplans containing partitions to allow subplans to be eliminated due to
159156
* the clauses being unable to match to any tuple that the subplan could
160-
* possibly produce.
157+
* possibly produce. Note that we currently support only one partitioned
158+
* table per parent plan node, hence partprunedata[] need describe only one
159+
* partitioning hierarchy.
161160
*
162-
* partprunedataArray of PartitionPruningData for the plan's target
163-
*partitioned relation. First element contains the
164-
*details for the target partitioned table.
161+
* partprunedataArray of PartitionPruningData for the plan's
162+
*partitioned relation, ordered such that parent tables
163+
*appear before children (hence, topmost table is first).
165164
* num_partprunedataNumber of items in 'partprunedata' array.
166165
* do_initial_prunetrue if pruning should be performed during executor
167166
*startup (at any hierarchy level).

‎src/include/nodes/plannodes.h

Lines changed: 22 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1059,18 +1059,35 @@ typedef struct PlanRowMark
10591059
* plan types which support arbitrary numbers of subplans, such as Append.
10601060
* We also store various details to tell the executor when it should be
10611061
* performing partition pruning.
1062+
*
1063+
* Each PartitionPruneInfo describes the partitioning rules for a single
1064+
* partitioned table (a/k/a level of partitioning). For a multilevel
1065+
* partitioned table, we have a List of PartitionPruneInfos, where the
1066+
* first entry represents the topmost partitioned table and additional
1067+
* entries represent non-leaf child partitions, ordered such that parents
1068+
* appear before their children.
1069+
*
1070+
* subplan_map[] and subpart_map[] are indexed by partition index (where
1071+
* zero is the topmost partition, and non-leaf partitions must come before
1072+
* their children). For a leaf partition p, subplan_map[p] contains the
1073+
* zero-based index of the partition's subplan in the parent plan's subplan
1074+
* list; it is -1 if the partition is non-leaf or has been pruned. For a
1075+
* non-leaf partition p, subpart_map[p] contains the zero-based index of
1076+
* that sub-partition's PartitionPruneInfo in the plan's PartitionPruneInfo
1077+
* list; it is -1 if the partition is a leaf or has been pruned. All these
1078+
* indexes are global across the whole partitioned table and Append plan node.
10621079
*/
10631080
typedefstructPartitionPruneInfo
10641081
{
10651082
NodeTagtype;
1066-
Oidreloid;/*Oid of partition rel */
1083+
Oidreloid;/*OID of partition rel for this level */
10671084
List*pruning_steps;/* List of PartitionPruneStep, see below */
1068-
Bitmapset*present_parts;/* Indexes of all partitions which subplans
1069-
* are present for. */
1085+
Bitmapset*present_parts;/* Indexes of all partitions which subplans or
1086+
*subpartsare present for. */
10701087
intnparts;/* Length of subplan_map[] and subpart_map[] */
10711088
intnexprs;/* Length of hasexecparam[] */
1072-
int*subplan_map;/* subplan index by partitionid, or -1 */
1073-
int*subpart_map;/* subpart index by partitionid, or -1 */
1089+
int*subplan_map;/* subplan index by partitionindex, or -1 */
1090+
int*subpart_map;/* subpart index by partitionindex, or -1 */
10741091
bool*hasexecparam;/* true if corresponding pruning_step contains
10751092
* any PARAM_EXEC Params. */
10761093
booldo_initial_prune;/* true if pruning should be performed

‎src/include/nodes/relation.h

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -552,8 +552,8 @@ typedef struct PartitionSchemeData *PartitionScheme;
552552
*part_rels - RelOptInfos for each partition
553553
*partexprs, nullable_partexprs - Partition key expressions
554554
*partitioned_child_rels - RT indexes of unpruned partitions of
555-
* relation that are partitioned tables
556-
* themselves
555+
*thisrelation that are partitioned tables
556+
* themselves, in hierarchical order
557557
*
558558
* Note: A base relation always has only one set of partition keys, but a join
559559
* relation may have as many sets of partition keys as the number of relations

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