sql: remove manually split ranges during TRUNCATE and DROP

If a table/index is dropped/truncated, any manually split ranges in the
table/index should be unsplit so the automatic merge queue can clean up
after it.

Additionally, re-enable splits in clearrange which was previously
timing out because manual splits could not be automatically merged.

Release note: None

pkg/cmd/roachtest/clearrange.go

@@ -52,12 +52,8 @@ func runClearRange(ctx context.Context, t *test, c *cluster, aggressiveChecks bo
 
 		// NB: on a 10 node cluster, this should take well below 3h.
 		tBegin := timeutil.Now()
-		// Currently we must set `--ranges=0` since automatic merges cannot merge ranges created by
-		// manual splits, and dropping the table does not remove manual splits. The latter may change
-		// in the future in which case it'll be fine to set `--ranges` to something else. But for now,
-		// setting it to nonzero causes the test to hang forever waiting on ranges to be merged.
 		c.Run(ctx, c.Node(1), "./cockroach", "workload", "fixtures", "import", "bank",
-			"--payload-bytes=10240", "--ranges=0", "--rows=65104166", "--seed=4", "--db=bigbank")
+			"--payload-bytes=10240", "--ranges=10", "--rows=65104166", "--seed=4", "--db=bigbank")
 		c.l.Printf("import took %.2fs", timeutil.Since(tBegin).Seconds())
 		c.Stop(ctx)
 		t.Status()

pkg/sql/drop_index.go

@@ -16,10 +16,12 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgerror"
 	"github.com/cockroachdb/cockroach/pkg/sql/privilege"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
+	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/pkg/errors"
 )
 
@@ -223,6 +225,28 @@ func (p *planner) dropIndexByName(
 	found := false
 	for i, idxEntry := range tableDesc.Indexes {
 		if idxEntry.ID == idx.ID {
+			// Unsplit all manually split ranges in the index so they can be
+			// automatically merged by the merge queue.
+			span := tableDesc.IndexSpan(idxEntry.ID)
+			ranges, err := ScanMetaKVs(ctx, p.txn, span)
+			if err != nil {
+				return err
+			}
+			for _, r := range ranges {
+				var desc roachpb.RangeDescriptor
+				if err := r.ValueProto(&desc); err != nil {
+					return err
+				}
+				// We have to explicitly check that the range descriptor's start key
+				// lies within the span of the index since ScanMetaKVs returns all
+				// intersecting spans.
+				if (desc.StickyBit != hlc.Timestamp{}) && span.Key.Compare(desc.StartKey.AsRawKey()) <= 0 {
+					if err := p.ExecCfg().DB.AdminUnsplit(ctx, desc.StartKey); err != nil {
+						return err
+					}
+				}
+			}
+
 			// the idx we picked up with FindIndexByID at the top may not
 			// contain the same field any more due to other schema changes
 			// intervening since the initial lookup. So we send the recent

pkg/sql/drop_table.go

@@ -19,10 +19,12 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/jobs"
 	"github.com/cockroachdb/cockroach/pkg/jobs/jobspb"
 	"github.com/cockroachdb/cockroach/pkg/keys"
+	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgerror"
 	"github.com/cockroachdb/cockroach/pkg/sql/privilege"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
+	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
 	"github.com/pkg/errors"
@@ -353,6 +355,24 @@ func (p *planner) initiateDropTable(
 		tableDesc.DropTime = timeutil.Now().UnixNano()
 	}
 
+	// Unsplit all manually split ranges in the table so they can be
+	// automatically merged by the merge queue.
+	ranges, err := ScanMetaKVs(ctx, p.txn, tableDesc.TableSpan())
+	if err != nil {
+		return err
+	}
+	for _, r := range ranges {
+		var desc roachpb.RangeDescriptor
+		if err := r.ValueProto(&desc); err != nil {
+			return err
+		}
+		if (desc.StickyBit != hlc.Timestamp{}) {
+			if err := p.ExecCfg().DB.AdminUnsplit(ctx, desc.StartKey); err != nil {
+				return err
+			}
+		}
+	}
+
 	tableDesc.State = sqlbase.TableDescriptor_DROP
 	if drainName {
 		// Queue up name for draining.

pkg/sql/logictest/testdata/logic_test/crdb_internal

@@ -325,7 +325,7 @@ node_id  store_id  attrs  used
 1        1         []     0
 
 statement ok
-CREATE TABLE foo (a INT PRIMARY KEY); INSERT INTO foo VALUES(1)
+CREATE TABLE foo (a INT PRIMARY KEY, INDEX idx(a)); INSERT INTO foo VALUES(1)
 
 statement ok
 ALTER TABLE foo SPLIT AT VALUES(2)
@@ -485,3 +485,56 @@ ORDER BY key, f
 SELECT crdb_internal.force_retry(_)  true  false
 SELECT crdb_internal.force_retry(_)  true  true
 SET application_name = DEFAULT       false false
+
+
+# Testing split_enforced_until when truncating and dropping.
+statement ok
+ALTER TABLE foo SPLIT AT VALUES (1), (2), (3)
+
+statement ok
+ALTER INDEX foo@idx SPLIT AT VALUES (1), (2), (3)
+
+statement ok
+TRUNCATE TABLE foo
+
+query TT colnames
+SELECT start_pretty, end_pretty FROM crdb_internal.ranges WHERE split_enforced_until IS NOT NULL
+----
+start_pretty   end_pretty
+
+query TT colnames
+SELECT start_pretty, end_pretty FROM crdb_internal.ranges_no_leases WHERE split_enforced_until IS NOT NULL
+----
+start_pretty   end_pretty
+
+statement ok
+ALTER INDEX foo@idx SPLIT AT VALUES (1), (2), (3)
+
+statement ok
+DROP INDEX foo@idx
+
+query TT colnames
+SELECT start_pretty, end_pretty FROM crdb_internal.ranges WHERE split_enforced_until IS NOT NULL
+----
+start_pretty   end_pretty
+
+query TT colnames
+SELECT start_pretty, end_pretty FROM crdb_internal.ranges_no_leases WHERE split_enforced_until IS NOT NULL
+----
+start_pretty   end_pretty
+
+statement ok
+ALTER TABLE foo SPLIT AT VALUES (1), (2), (3)
+
+statement ok
+DROP TABLE foo
+
+query TT colnames
+SELECT start_pretty, end_pretty FROM crdb_internal.ranges WHERE split_enforced_until IS NOT NULL
+----
+start_pretty   end_pretty
+
+query TT colnames
+SELECT start_pretty, end_pretty FROM crdb_internal.ranges_no_leases WHERE split_enforced_until IS NOT NULL
+----
+start_pretty   end_pretty