sql: change SPLIT AT to take a select statement

`SPLIT AT` now takes an arbitrary select statement. Existing uses must switch to
using `VALUES`; e.g. `ALTER TABLE t SPLIT AT (x, y)` becomes `ALTER TABLE t
SPLIT AT VALUES (x, y)`.

Part of cockroachdb#13665, implements part of RFC cockroachdb#14146.

pkg/ccl/sqlccl/backup_test.go

@@ -78,18 +78,23 @@ func bankDataInsertStmts(count int) []string {
 	return statements
 }
 
-func bankSplitStmts(numAccounts int, numRanges int) []string {
+func bankSplitStmt(numAccounts int, numRanges int) string {
 	// Asking for more splits than ranges doesn't make any sense. Because of the
 	// way go benchmarks work, split each row into a range instead of erroring.
 	if numRanges > numAccounts {
 		numRanges = numAccounts
 	}
-	var statements []string
+
+	var stmt bytes.Buffer
+	stmt.WriteString("ALTER TABLE bench.bank SPLIT AT VALUES ")
+
 	for i, incr := 1, numAccounts/numRanges; i < numRanges; i++ {
-		s := fmt.Sprintf(`ALTER TABLE bench.bank SPLIT AT (%d)`, i*incr)
-		statements = append(statements, s)
+		if i > 1 {
+			stmt.WriteString(", ")
+		}
+		fmt.Fprintf(&stmt, "(%d)", i*incr)
 	}
-	return statements
+	return stmt.String()
 }
 
 func backupRestoreTestSetup(
@@ -115,10 +120,9 @@ func backupRestoreTestSetup(
 		for _, insert := range bankDataInsertStmts(numAccounts) {
 			sqlDB.Exec(insert)
 		}
-		for _, split := range bankSplitStmts(numAccounts, backupRestoreDefaultRanges) {
-			// This occasionally flakes, so ignore errors.
-			_, _ = sqlDB.DB.Exec(split)
-		}
+		split := bankSplitStmt(numAccounts, backupRestoreDefaultRanges)
+		// This occasionally flakes, so ignore errors.
+		_, _ = sqlDB.DB.Exec(split)
 	}
 
 	if err := tc.WaitForFullReplication(); err != nil {

pkg/ccl/storageccl/export_test.go

@@ -109,7 +109,7 @@ func TestExport(t *testing.T) {
 		t.Fatalf("expected a deletion tombstone got %s", v.PrettyPrint())
 	}
 
-	sqlDB.Exec(`ALTER TABLE export.export SPLIT AT (2)`)
+	sqlDB.Exec(`ALTER TABLE export.export SPLIT AT VALUES (2)`)
 	_, paths5, kvs5 := exportAndSlurp(hlc.Timestamp{})
 	if expected := 2; len(paths5) != expected {
 		t.Fatalf("expected %d files in export got %d", expected, len(paths5))

pkg/sql/parser/parse_test.go

@@ -615,12 +615,13 @@ func TestParse(t *testing.T) {
 		{`COPY t FROM STDIN`},
 		{`COPY t (a, b, c) FROM STDIN`},
 
-		{`ALTER TABLE a SPLIT AT (1)`},
-		{`ALTER TABLE d.a SPLIT AT ('b', 2)`},
-		{`ALTER INDEX a@i SPLIT AT (1)`},
-		{`ALTER INDEX d.a@i SPLIT AT (2)`},
-		{`ALTER INDEX i SPLIT AT (1)`},
-		{`ALTER INDEX d.i SPLIT AT (2)`},
+		{`ALTER TABLE a SPLIT AT VALUES (1)`},
+		{`ALTER TABLE a SPLIT AT SELECT * FROM t`},
+		{`ALTER TABLE d.a SPLIT AT VALUES ('b', 2)`},
+		{`ALTER INDEX a@i SPLIT AT VALUES (1)`},
+		{`ALTER INDEX d.a@i SPLIT AT VALUES (2)`},
+		{`ALTER INDEX i SPLIT AT VALUES (1)`},
+		{`ALTER INDEX d.i SPLIT AT VALUES (2)`},
 
 		{`BACKUP foo TO 'bar'`},
 		{`BACKUP foo.foo, baz.baz TO 'bar'`},

pkg/sql/parser/split.go

@@ -22,7 +22,9 @@ import "bytes"
 type Split struct {
 	Table NormalizableTableName
 	Index *TableNameWithIndex
-	Exprs Exprs
+	// Each row contains values for the columns in the PK or index (or a prefix
+	// of the columns).
+	Rows *Select
 }
 
 // Format implements the NodeFormatter interface.
@@ -35,7 +37,6 @@ func (node *Split) Format(buf *bytes.Buffer, f FmtFlags) {
 		buf.WriteString("TABLE ")
 		FormatNode(buf, f, node.Table)
 	}
-	buf.WriteString(" SPLIT AT (")
-	FormatNode(buf, f, node.Exprs)
-	buf.WriteString(")")
+	buf.WriteString(" SPLIT AT ")
+	FormatNode(buf, f, node.Rows)
 }