catalog: Improve alter column type (#818)

* catalog: Improve alter column type

This commit adds support for altering a column type into an array. It
adds a new test to ensure that the generated code is valid.

* catalog: remove unecessary type annotation

* ast: Add a String method to AlterTableType

Author: aitva

internal/endtoend/testdata/ddl_alter_table_alter_type/postgresql/go/db.go

@@ -0,0 +1,2 @@
+-- name: Placeholder :exec
+SELECT 1;

internal/endtoend/testdata/ddl_alter_table_alter_type/postgresql/go/models.go

@@ -0,0 +1,2 @@
+CREATE TABLE foo (bar TEXT);
+ALTER TABLE foo ALTER bar TYPE TEXT ARRAY;

internal/endtoend/testdata/ddl_alter_table_alter_type/postgresql/go/query.sql.go

@@ -0,0 +1,12 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "name": "querytest",
+      "schema": "schema.sql",
+      "queries": "query.sql"
+    }
+  ]
+}

internal/endtoend/testdata/ddl_alter_table_alter_type/postgresql/query.sql

@@ -1,7 +1,5 @@
 package ast
 
-type AlterTableType int
-
 const (
 	AT_AddColumn AlterTableType = iota
 	AT_AlterColumnType
@@ -10,6 +8,25 @@ const (
 	AT_SetNotNull
 )
 
+type AlterTableType int
+
+func (t AlterTableType) String() string {
+	switch t {
+	case AT_AddColumn:
+		return "AddColumn"
+	case AT_AlterColumnType:
+		return "AlterColumnType"
+	case AT_DropColumn:
+		return "DropColumn"
+	case AT_DropNotNull:
+		return "DropNotNull"
+	case AT_SetNotNull:
+		return "SetNotNull"
+	default:
+		return "Unknown"
+	}
+}
+
 type AlterTableCmd struct {
 	Subtype   AlterTableType
 	Name      *string

internal/endtoend/testdata/ddl_alter_table_alter_type/postgresql/schema.sql

@@ -258,7 +258,7 @@ func New(def string) *Catalog {
 	return &Catalog{
 		DefaultSchema: def,
 		Schemas: []*Schema{
-			&Schema{Name: def},
+			{Name: def},
 		},
 		Extensions: map[string]struct{}{},
 	}

internal/endtoend/testdata/ddl_alter_table_alter_type/postgresql/sqlc.json

@@ -78,7 +78,7 @@ func (c *Catalog) alterTable(stmt *ast.AlterTableStmt) error {
 
 			case ast.AT_AlterColumnType:
 				table.Columns[idx].Type = *cmd.Def.TypeName
-				// table.Columns[idx].IsArray = isArray(d.TypeName)
+				table.Columns[idx].IsArray = cmd.Def.IsArray
 
 			case ast.AT_DropColumn:
 				table.Columns = append(table.Columns[:idx], table.Columns[idx+1:]...)