Release note (sql change): When a hash sharded index is partitioned,

ranges are pre-split within every single possible partition on shard
boundaries. Each partition is split up to 16 ranges, otherwise split
into the number bucket count ranges.

pkg/ccl/logictestccl/testdata/logic_test/partitioning_hash_sharded_index

@@ -1380,3 +1380,46 @@ vectorized: true
                     └── • scan buffer
                           columns: (id, email, part, crdb_internal_email_shard_16, email_new, crdb_internal_email_shard_16_cast, check2)
                           label: buffer 1
+
+subtest test_presplit_with_partitioning
+
+statement ok
+CREATE TABLE t_presplit (
+  user_id INT PRIMARY KEY,
+  city STRING NOT NULL CHECK (city IN ('seattle', 'new york')),
+  member_id INT
+) PARTITION ALL BY LIST (city) (
+    PARTITION us_west VALUES IN (('seattle')),
+    PARTITION us_east VALUES IN (('new york'))
+);
+
+statement ok
+CREATE INDEX t_presplit_idx_member_id ON t_presplit (member_id) USING HASH WITH (bucket_count=8);
+
+skipif config 3node-tenant
+query TITTT colnames,retry
+SELECT t.name, r.table_id, r.index_name, r.start_pretty, r.end_pretty
+FROM crdb_internal.tables t
+JOIN crdb_internal.ranges r ON t.table_id = r.table_id
+WHERE t.name = 't_presplit'
+AND t.state = 'PUBLIC'
+AND r.split_enforced_until IS NOT NULL;
+----
+name        table_id  index_name                start_pretty               end_pretty
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2               /Table/116/2/"new york"/0
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/0  /Table/116/2/"new york"/1
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/1  /Table/116/2/"new york"/2
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/2  /Table/116/2/"new york"/3
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/3  /Table/116/2/"new york"/4
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/4  /Table/116/2/"new york"/5
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/5  /Table/116/2/"new york"/6
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/6  /Table/116/2/"new york"/7
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"new york"/7  /Table/116/2/"seattle"/0
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/0   /Table/116/2/"seattle"/1
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/1   /Table/116/2/"seattle"/2
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/2   /Table/116/2/"seattle"/3
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/3   /Table/116/2/"seattle"/4
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/4   /Table/116/2/"seattle"/5
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/5   /Table/116/2/"seattle"/6
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/6   /Table/116/2/"seattle"/7
+t_presplit  116       t_presplit_idx_member_id  /Table/116/2/"seattle"/7   /Max

pkg/sql/schema_changer.go

@@ -43,6 +43,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/parser"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgcode"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgerror"
+	"github.com/cockroachdb/cockroach/pkg/sql/rowenc"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/sessiondata"
 	"github.com/cockroachdb/cockroach/pkg/sql/sessiondatapb"
@@ -2655,14 +2656,49 @@ func (sc *SchemaChanger) preSplitHashShardedIndexRanges(ctx context.Context) err
 			}
 
 			if idx := m.AsIndex(); m.Adding() && m.DeleteOnly() && idx != nil {
-				// TODO (issue #76507): also pre-split partitioned hash sharded index.
-				if idx.IsSharded() && idx.GetPartitioning().PartitioningDesc().NumImplicitColumns == 0 {
+				if idx.IsSharded() {
+					var partitionKeyPrefixes []roachpb.Key
+					partitioning := idx.GetPartitioning()
+					partitioning.ForEachList(
+						func(name string, values [][]byte, subPartitioning catalog.Partitioning) error {
+							for _, tupleBytes := range values {
+								_, key, err := rowenc.DecodePartitionTuple(
+									&tree.DatumAlloc{},
+									sc.execCfg.Codec,
+									tableDesc,
+									idx,
+									partitioning,
+									tupleBytes,
+									tree.Datums{},
+								)
+								if err != nil {
+									return nil
+								}
+								partitionKeyPrefixes = append(partitionKeyPrefixes, key)
+							}
+							return nil
+						},
+					)
+
 					splitAtShards := calculateSplitAtShards(maxHashShardedIndexRangePreSplit.Get(&sc.settings.SV), idx.GetSharded().ShardBuckets)
-					for _, shard := range splitAtShards {
-						keyPrefix := sc.execCfg.Codec.IndexPrefix(uint32(tableDesc.GetID()), uint32(idx.GetID()))
-						splitKey := encoding.EncodeVarintAscending(keyPrefix, shard)
-						if err := sc.db.SplitAndScatter(ctx, splitKey, hour); err != nil {
-							return err
+					if len(partitionKeyPrefixes) == 0 {
+						// If there is no partitioning on the index, only pre-split on
+						// selected shard boundaries.
+						for _, shard := range splitAtShards {
+							keyPrefix := sc.execCfg.Codec.IndexPrefix(uint32(tableDesc.GetID()), uint32(idx.GetID()))
+							splitKey := encoding.EncodeVarintAscending(keyPrefix, shard)
+							if err := sc.db.SplitAndScatter(ctx, splitKey, hour); err != nil {
+								return err
+							}
+						}
+					} else {
+						for _, partPrefix := range partitionKeyPrefixes {
+							for _, shard := range splitAtShards {
+								splitKey := encoding.EncodeVarintAscending(partPrefix, shard)
+								if err := sc.db.SplitAndScatter(ctx, splitKey, hour); err != nil {
+									return err
+								}
+							}
 						}
 					}
 				}