Allow SHOW CREATE to display auto increment for tables that store AutoIncrement but don't support writing it.

sql/rowexec/show_iters.go

@@ -531,9 +531,9 @@ func getForeignKeyTable(t sql.Table) (sql.ForeignKeyTable, error) {
 	}
 }
 
-func getAutoIncrementTable(t sql.Table) sql.AutoIncrementTable {
+func getAutoIncrementTable(t sql.Table) sql.AutoIncrementGetter {
 	switch t := t.(type) {
-	case sql.AutoIncrementTable:
+	case sql.AutoIncrementGetter:
 		return t
 	case sql.TableWrapper:
 		return getAutoIncrementTable(t.Underlying())

sql/tables.go

@@ -330,9 +330,7 @@ type TruncateableTable interface {
 // AUTO_INCREMENT sequence. These methods should only be used for tables with and AUTO_INCREMENT column in their schema.
 type AutoIncrementTable interface {
 	Table
-	// PeekNextAutoIncrementValue returns the next AUTO_INCREMENT value without incrementing the current
-	// auto_increment counter.
-	PeekNextAutoIncrementValue(ctx *Context) (uint64, error)
+	AutoIncrementGetter
 	// GetNextAutoIncrementValue gets the next AUTO_INCREMENT value. In the case that a table with an autoincrement
 	// column is passed in a row with the autoinc column failed, the next auto increment value must
 	// update its internal state accordingly and use the insert val at runtime.
@@ -342,6 +340,15 @@ type AutoIncrementTable interface {
 	AutoIncrementSetter(*Context) AutoIncrementSetter
 }
 
+// AutoIncrementGetter provides support for reading a table's AUTO_INCREMENT value.
+// This can include tables that don't implement AutoIncrementTable if the table is a read-only snapshot
+// of an auto-incremented table.
+type AutoIncrementGetter interface {
+	// PeekNextAutoIncrementValue returns the next AUTO_INCREMENT value without incrementing the current
+	// auto_increment counter.
+	PeekNextAutoIncrementValue(ctx *Context) (uint64, error)
+}
+
 // AutoIncrementSetter provides support for altering a table's
 // AUTO_INCREMENT sequence, eg 'ALTER TABLE t AUTO_INCREMENT = 10;'
 type AutoIncrementSetter interface {