On Thu, Feb 6, 2020 at 10:31 AM Amit Langote <amitlangot...@gmail.com> wrote:
> On Thu, Feb 6, 2020 at 8:44 AM Justin Pryzby <pry...@telsasoft.com> wrote:
> > On Wed, Feb 05, 2020 at 03:53:45PM +0900, Amit Langote wrote:
> > > diff --git a/src/test/regress/sql/alter_table.sql 
> > > b/src/test/regress/sql/alter_table.sql
> > > +-- alter type shouldn't lose clustered index
> >
> > My only suggestion is to update the comment
> > +-- alter type rewrite/rebuild should preserve cluster marking on index
>
> Sure, done.

Deja vu.  Last two messages weren't sent to the list; updated patch attached.

Thanks,
Amit
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f599393473..bab3ddf67c 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -490,6 +490,7 @@ static void ATPostAlterTypeParse(Oid oldId, Oid oldRelId, 
Oid refRelId,
 static void RebuildConstraintComment(AlteredTableInfo *tab, int pass,
                                                                         Oid 
objid, Relation rel, List *domname,
                                                                         const 
char *conname);
+static void PreserveClusterOn(AlteredTableInfo *tab, int pass, Oid indoid);
 static void TryReuseIndex(Oid oldId, IndexStmt *stmt);
 static void TryReuseForeignKey(Oid oldId, Constraint *con);
 static ObjectAddress ATExecAlterColumnGenericOptions(Relation rel, const char 
*colName,
@@ -11832,6 +11833,9 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid 
refRelId, char *cmd,
                        newcmd->def = (Node *) stmt;
                        tab->subcmds[AT_PASS_OLD_INDEX] =
                                lappend(tab->subcmds[AT_PASS_OLD_INDEX], 
newcmd);
+
+                       /* Preserve index's indisclustered property, if set. */
+                       PreserveClusterOn(tab, AT_PASS_OLD_INDEX, oldId);
                }
                else if (IsA(stm, AlterTableStmt))
                {
@@ -11868,6 +11872,9 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid 
refRelId, char *cmd,
                                                                                
         rel,
                                                                                
         NIL,
                                                                                
         indstmt->idxname);
+
+                                       /* Preserve index's indisclustered 
property, if set. */
+                                       PreserveClusterOn(tab, 
AT_PASS_OLD_INDEX, indoid);
                                }
                                else if (cmd->subtype == AT_AddConstraint)
                                {
@@ -11990,6 +11997,38 @@ RebuildConstraintComment(AlteredTableInfo *tab, int 
pass, Oid objid,
        tab->subcmds[pass] = lappend(tab->subcmds[pass], newcmd);
 }
 
+/*
+ * For a table's index that is to be recreated due to PostAlterType
+ * processing, preserve its indisclustered property by issuing ALTER TABLE
+ * CLUSTER ON command on the table that will run after the command to recreate
+ * the index.
+ */
+static void
+PreserveClusterOn(AlteredTableInfo *tab, int pass, Oid indoid)
+{
+       HeapTuple       indexTuple;
+       Form_pg_index indexForm;
+
+       Assert(OidIsValid(indoid));
+       Assert(pass == AT_PASS_OLD_INDEX);
+
+       indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indoid));
+       if (!HeapTupleIsValid(indexTuple))
+               elog(ERROR, "cache lookup failed for index %u", indoid);
+       indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
+
+       if (indexForm->indisclustered)
+       {
+               AlterTableCmd *newcmd = makeNode(AlterTableCmd);
+
+               newcmd->subtype = AT_ClusterOn;
+               newcmd->name = get_rel_name(indoid);
+               tab->subcmds[pass] = lappend(tab->subcmds[pass], newcmd);
+       }
+
+       ReleaseSysCache(indexTuple);
+}
+
 /*
  * Subroutine for ATPostAlterTypeParse().  Calls out to CheckIndexCompatible()
  * for the real analysis, then mutates the IndexStmt based on that verdict.
diff --git a/src/test/regress/expected/alter_table.out 
b/src/test/regress/expected/alter_table.out
index e73ce4b6f3..09c00eef05 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -4258,3 +4258,37 @@ alter table at_test_sql_partop attach partition 
at_test_sql_partop_1 for values
 drop table at_test_sql_partop;
 drop operator class at_test_sql_partop using btree;
 drop function at_test_sql_partop;
+-- alter type rewrite/rebuild should preserve cluster marking on index
+create table alttype_cluster (a int);
+create index alttype_cluster_a on alttype_cluster (a);
+alter table alttype_cluster cluster on alttype_cluster_a;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+ indisclustered 
+----------------
+ t
+(1 row)
+
+alter table alttype_cluster alter a type bigint;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+ indisclustered 
+----------------
+ t
+(1 row)
+
+drop index alttype_cluster_a;
+alter table alttype_cluster add primary key (a);
+alter table alttype_cluster cluster on alttype_cluster_pkey;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+ indisclustered 
+----------------
+ t
+(1 row)
+
+alter table alttype_cluster alter a type int;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+ indisclustered 
+----------------
+ t
+(1 row)
+
+drop table alttype_cluster;
diff --git a/src/test/regress/sql/alter_table.sql 
b/src/test/regress/sql/alter_table.sql
index a16e4c9a29..7e43965a86 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -2801,3 +2801,18 @@ alter table at_test_sql_partop attach partition 
at_test_sql_partop_1 for values
 drop table at_test_sql_partop;
 drop operator class at_test_sql_partop using btree;
 drop function at_test_sql_partop;
+
+-- alter type rewrite/rebuild should preserve cluster marking on index
+create table alttype_cluster (a int);
+create index alttype_cluster_a on alttype_cluster (a);
+alter table alttype_cluster cluster on alttype_cluster_a;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+alter table alttype_cluster alter a type bigint;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+drop index alttype_cluster_a;
+alter table alttype_cluster add primary key (a);
+alter table alttype_cluster cluster on alttype_cluster_pkey;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+alter table alttype_cluster alter a type int;
+select indisclustered from pg_index where indrelid = 
'alttype_cluster'::regclass;
+drop table alttype_cluster;

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