Обсуждение: = TRUE vs IS TRUE confuses partition index creation

This has been tested on 14.5 and 13.7.

When an index is created on the root of a (declarative) partitioned table, that index is also created on the children,
unlessthere is an existing index on that child that matches the definition of the new index.  It seems that using `=
TRUE`confuses it, compared to `IS TRUE`. 

Test case:

BEGIN;

CREATE TABLE public.t (
    id bigint NOT NULL,
    t timestamp without time zone NOT NULL,
    b boolean NOT NULL
) PARTITION BY RANGE (t);

CREATE TABLE public.t_older (
    id bigint NOT NULL,
    t timestamp without time zone NOT NULL,
    b boolean NOT NULL
);

CREATE INDEX ON public.t_older USING btree (id) WHERE b IS TRUE;
CREATE INDEX ON public.t_older USING btree (id) WHERE b = TRUE;

ALTER TABLE t ATTACH PARTITION t_older
    FOR VALUES FROM ('2010-01-01') TO ('2022-01-01');

CREATE INDEX ON public.t USING btree (id) WHERE b IS TRUE;
CREATE INDEX ON public.t USING btree (id) WHERE b = TRUE;

COMMIT;

The result is:

xof=# \d t
                     Partitioned table "public.t"
 Column |            Type             | Collation | Nullable | Default
--------+-----------------------------+-----------+----------+---------
 id     | bigint                      |           | not null |
 t      | timestamp without time zone |           | not null |
 b      | boolean                     |           | not null |
Partition key: RANGE (t)
Indexes:
    "t_id_idx" btree (id) WHERE b IS TRUE
    "t_id_idx1" btree (id) WHERE b = true
Number of partitions: 1 (Use \d+ to list them.)

fin_test=# \d t_older
                        Table "public.t_older"
 Column |            Type             | Collation | Nullable | Default
--------+-----------------------------+-----------+----------+---------
 id     | bigint                      |           | not null |
 t      | timestamp without time zone |           | not null |
 b      | boolean                     |           | not null |
Partition of: t FOR VALUES FROM ('2010-01-01 00:00:00') TO ('2022-01-01 00:00:00')
Indexes:
    "t_older_id_idx" btree (id) WHERE b IS TRUE -- Correctly does not create a new index
    "t_older_id_idx1" btree (id) WHERE b = true
    "t_older_id_idx2" btree (id) WHERE b = true -- Unexpected duplicated index

Christophe Pettus <xof@thebuild.com> writes:
> When an index is created on the root of a (declarative) partitioned table, that index is also created on the
children,unless there is an existing index on that child that matches the definition of the new index.  It seems that
using`= TRUE` confuses it, compared to `IS TRUE`. 

IIRC, "b = true" will be simplified to just "b" somewhere in expression
preprocessing.  I'm betting that something in the partitioned index
matching code is applying that preprocessing to one index predicate and
not the other, whereupon they look different.  If that's the explanation,
there are likely other cases that should match and fail to.

            regards, tom lane

Richard Guo <guofenglinux@gmail.com> writes:
>> This can be verified with the attached changes, which would make it work
>> for this case.

I don't like this patch too much, because it will result in opening
the new index, building an IndexInfo, and closing the index again
for each index of each partition.  We only need to do that once.

Another thing that struck me as poor practice was not getting the
other arguments of CompareIndexInfo (opfamilies and collation)
from the new index.  At best this is making the code know more
than it needs to.

Hence, v2 patch attached, now with a test case.

            regards, tom lane

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 15a57ea9c3..667f2a4cd1 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -1213,18 +1213,27 @@ DefineIndex(Oid relationId,
             int            nparts = partdesc->nparts;
             Oid           *part_oids = palloc(sizeof(Oid) * nparts);
             bool        invalidate_parent = false;
+            Relation    parentIndex;
             TupleDesc    parentDesc;
-            Oid           *opfamOids;

             pgstat_progress_update_param(PROGRESS_CREATEIDX_PARTITIONS_TOTAL,
                                          nparts);

+            /* Make a local copy of partdesc->oids[], just for safety */
             memcpy(part_oids, partdesc->oids, sizeof(Oid) * nparts);

+            /*
+             * We'll need an IndexInfo describing the parent index.  The one
+             * built above is almost good enough, but not quite, because (for
+             * example) its predicate expression if any hasn't been through
+             * expression preprocessing.  The most reliable way to get an
+             * IndexInfo that will match those for child indexes is to build
+             * it the same way, using BuildIndexInfo().
+             */
+            parentIndex = index_open(indexRelationId, lockmode);
+            indexInfo = BuildIndexInfo(parentIndex);
+
             parentDesc = RelationGetDescr(rel);
-            opfamOids = palloc(sizeof(Oid) * numberOfKeyAttributes);
-            for (i = 0; i < numberOfKeyAttributes; i++)
-                opfamOids[i] = get_opclass_family(classObjectId[i]);

             /*
              * For each partition, scan all existing indexes; if one matches
@@ -1295,9 +1304,9 @@ DefineIndex(Oid relationId,
                     cldIdxInfo = BuildIndexInfo(cldidx);
                     if (CompareIndexInfo(cldIdxInfo, indexInfo,
                                          cldidx->rd_indcollation,
-                                         collationObjectId,
+                                         parentIndex->rd_indcollation,
                                          cldidx->rd_opfamily,
-                                         opfamOids,
+                                         parentIndex->rd_opfamily,
                                          attmap))
                     {
                         Oid            cldConstrOid = InvalidOid;
@@ -1424,6 +1433,8 @@ DefineIndex(Oid relationId,
                 free_attrmap(attmap);
             }

+            index_close(parentIndex, lockmode);
+
             /*
              * The pg_index row we inserted for this index was marked
              * indisvalid=true.  But if we attached an existing index that is
diff --git a/src/test/regress/expected/indexing.out b/src/test/regress/expected/indexing.out
index 193f780191..1bdd430f06 100644
--- a/src/test/regress/expected/indexing.out
+++ b/src/test/regress/expected/indexing.out
@@ -378,7 +378,7 @@ drop table idxpart;
 -- When a table is attached a partition and it already has an index, a
 -- duplicate index should not get created, but rather the index becomes
 -- attached to the parent's index.
-create table idxpart (a int, b int, c text) partition by range (a);
+create table idxpart (a int, b int, c text, d bool) partition by range (a);
 create index idxparti on idxpart (a);
 create index idxparti2 on idxpart (b, c);
 create table idxpart1 (like idxpart including indexes);
@@ -389,6 +389,7 @@ create table idxpart1 (like idxpart including indexes);
  a      | integer |           |          |
  b      | integer |           |          |
  c      | text    |           |          |
+ d      | boolean |           |          |
 Indexes:
     "idxpart1_a_idx" btree (a)
     "idxpart1_b_c_idx" btree (b, c)
@@ -415,6 +416,7 @@ alter table idxpart attach partition idxpart1 for values from (0) to (10);
  a      | integer |           |          |
  b      | integer |           |          |
  c      | text    |           |          |
+ d      | boolean |           |          |
 Partition of: idxpart FOR VALUES FROM (0) TO (10)
 Indexes:
     "idxpart1_a_idx" btree (a)
@@ -434,6 +436,68 @@ select relname, relkind, inhparent::regclass
  idxparti2        | I       |
 (6 rows)

+-- While here, also check matching when creating an index after the fact.
+create index on idxpart1 ((a+b)) where d = true;
+\d idxpart1
+              Table "public.idxpart1"
+ Column |  Type   | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ a      | integer |           |          |
+ b      | integer |           |          |
+ c      | text    |           |          |
+ d      | boolean |           |          |
+Partition of: idxpart FOR VALUES FROM (0) TO (10)
+Indexes:
+    "idxpart1_a_idx" btree (a)
+    "idxpart1_b_c_idx" btree (b, c)
+    "idxpart1_expr_idx" btree ((a + b)) WHERE d = true
+
+select relname, relkind, inhparent::regclass
+    from pg_class left join pg_index ix on (indexrelid = oid)
+    left join pg_inherits on (ix.indexrelid = inhrelid)
+    where relname like 'idxpart%' order by relname;
+      relname      | relkind | inhparent
+-------------------+---------+-----------
+ idxpart           | p       |
+ idxpart1          | r       |
+ idxpart1_a_idx    | i       | idxparti
+ idxpart1_b_c_idx  | i       | idxparti2
+ idxpart1_expr_idx | i       |
+ idxparti          | I       |
+ idxparti2         | I       |
+(7 rows)
+
+create index idxparti3 on idxpart ((a+b)) where d = true;
+\d idxpart1
+              Table "public.idxpart1"
+ Column |  Type   | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ a      | integer |           |          |
+ b      | integer |           |          |
+ c      | text    |           |          |
+ d      | boolean |           |          |
+Partition of: idxpart FOR VALUES FROM (0) TO (10)
+Indexes:
+    "idxpart1_a_idx" btree (a)
+    "idxpart1_b_c_idx" btree (b, c)
+    "idxpart1_expr_idx" btree ((a + b)) WHERE d = true
+
+select relname, relkind, inhparent::regclass
+    from pg_class left join pg_index ix on (indexrelid = oid)
+    left join pg_inherits on (ix.indexrelid = inhrelid)
+    where relname like 'idxpart%' order by relname;
+      relname      | relkind | inhparent
+-------------------+---------+-----------
+ idxpart           | p       |
+ idxpart1          | r       |
+ idxpart1_a_idx    | i       | idxparti
+ idxpart1_b_c_idx  | i       | idxparti2
+ idxpart1_expr_idx | i       | idxparti3
+ idxparti          | I       |
+ idxparti2         | I       |
+ idxparti3         | I       |
+(8 rows)
+
 drop table idxpart;
 -- Verify that attaching an invalid index does not mark the parent index valid.
 -- On the other hand, attaching a valid index marks not only its direct
diff --git a/src/test/regress/sql/indexing.sql b/src/test/regress/sql/indexing.sql
index 42f398b67c..429120e710 100644
--- a/src/test/regress/sql/indexing.sql
+++ b/src/test/regress/sql/indexing.sql
@@ -192,7 +192,7 @@ drop table idxpart;
 -- When a table is attached a partition and it already has an index, a
 -- duplicate index should not get created, but rather the index becomes
 -- attached to the parent's index.
-create table idxpart (a int, b int, c text) partition by range (a);
+create table idxpart (a int, b int, c text, d bool) partition by range (a);
 create index idxparti on idxpart (a);
 create index idxparti2 on idxpart (b, c);
 create table idxpart1 (like idxpart including indexes);
@@ -203,6 +203,19 @@ select relname, relkind, inhparent::regclass
     where relname like 'idxpart%' order by relname;
 alter table idxpart attach partition idxpart1 for values from (0) to (10);
 \d idxpart1
+select relname, relkind, inhparent::regclass
+    from pg_class left join pg_index ix on (indexrelid = oid)
+    left join pg_inherits on (ix.indexrelid = inhrelid)
+    where relname like 'idxpart%' order by relname;
+-- While here, also check matching when creating an index after the fact.
+create index on idxpart1 ((a+b)) where d = true;
+\d idxpart1
+select relname, relkind, inhparent::regclass
+    from pg_class left join pg_index ix on (indexrelid = oid)
+    left join pg_inherits on (ix.indexrelid = inhrelid)
+    where relname like 'idxpart%' order by relname;
+create index idxparti3 on idxpart ((a+b)) where d = true;
+\d idxpart1
 select relname, relkind, inhparent::regclass
     from pg_class left join pg_index ix on (indexrelid = oid)
     left join pg_inherits on (ix.indexrelid = inhrelid)

Richard Guo <guofenglinux@gmail.com> writes:
> Thanks. The v2 patch is a good improvement on the two aspects. It's in
> good shape to me.

Pushed that version.

            regards, tom lane