From ceda4ab61bc04dfdddfc4ec55938d499ca1e6c4c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kuba=20Podg=C3=B3rski?= <kuba--@users.noreply.github.com>
Date: Mon, 24 Aug 2020 13:24:18 +0200
Subject: [PATCH] Add support for drop table

---
 server/grpc_test.go | 25 +++++++++++++++++
 server/sql.go       | 11 +++-----
 sql/ddl.go          | 65 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+), 7 deletions(-)
 create mode 100644 sql/ddl.go

diff --git a/server/grpc_test.go b/server/grpc_test.go
index 4529c0df8..77c030e23 100644
--- a/server/grpc_test.go
+++ b/server/grpc_test.go
@@ -709,6 +709,7 @@ func TestQuerySQLUnary(t *testing.T) {
 					{"Table", "string"},
 				},
 				rows: []row{
+					{[]columnResponse{"delete_me"}},
 					{[]columnResponse{"grouper"}},
 					{[]columnResponse{"joiner"}},
 				},
@@ -731,6 +732,27 @@ func TestQuerySQLUnary(t *testing.T) {
 			},
 			eq: equal,
 		},
+		{
+			sql: "drop table delete_me",
+			exp: tableResponse{
+				headers: []columnInfo{},
+				rows:    []row{},
+			},
+			eq: equal,
+		},
+		{
+			sql: "show tables",
+			exp: tableResponse{
+				headers: []columnInfo{
+					{"Table", "string"},
+				},
+				rows: []row{
+					{[]columnResponse{"grouper"}},
+					{[]columnResponse{"joiner"}},
+				},
+			},
+			eq: equal,
+		},
 	}
 
 	for i, test := range tests {
@@ -881,6 +903,9 @@ func setUpTestQuerySQLUnary(ctx context.Context, t *testing.T) (gh *server.GRPCH
 		}
 	}
 
+	// delete_me
+	m.MustCreateIndex(t, "delete_me", pilosa.IndexOptions{TrackExistence: true})
+
 	return gh, func() {
 		if err := m.API.DeleteIndex(ctx, joiner.Name()); err != nil {
 			panic(err)
diff --git a/server/sql.go b/server/sql.go
index 0f1de916c..7647e0377 100644
--- a/server/sql.go
+++ b/server/sql.go
@@ -38,17 +38,14 @@ func execSQL(ctx context.Context, api *pilosa.API, logger logger.Logger, querySt
 	case sql.SQLTypeSelect:
 		handler := sql.NewSelectHandler(api)
 		results, err = handler.Handle(ctx, query)
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to start SQL query")
-		}
 	case sql.SQLTypeShow:
 		handler := sql.NewShowHandler(api)
 		results, err = handler.Handle(ctx, query)
-		if err != nil {
-			return nil, errors.Wrap(err, "failed to start SQL query")
-		}
+	case sql.SQLTypeEmpty:
+		handler := sql.NewDDLHandler(api)
+		results, err = handler.Handle(ctx, query)
 	default:
 		return nil, status.Errorf(codes.Unimplemented, "query type not supported")
 	}
-	return results, nil
+	return results, errors.Wrap(err, "failed to start SQL query")
 }
diff --git a/sql/ddl.go b/sql/ddl.go
new file mode 100644
index 000000000..3b693850e
--- /dev/null
+++ b/sql/ddl.go
@@ -0,0 +1,65 @@
+// Copyright 2020 Pilosa Corp.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sql
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/pilosa/pilosa/v2"
+	pproto "github.com/pilosa/pilosa/v2/proto"
+	"github.com/pkg/errors"
+	"vitess.io/vitess/go/vt/sqlparser"
+)
+
+// DDLHandler executes  CREATE, ALTER, DROP, RENAME, TRUNCATE or ANALYZE statement.
+type DDLHandler struct {
+	api *pilosa.API
+}
+
+// NewDDLHandler constructor
+func NewDDLHandler(api *pilosa.API) *DDLHandler {
+	return &DDLHandler{
+		api: api,
+	}
+}
+
+// Handle executes mapped SQL
+func (h *DDLHandler) Handle(ctx context.Context, mapped *MappedSQL) (pproto.StreamClient, error) {
+	stmt, ok := mapped.Statement.(*sqlparser.DDL)
+	if !ok {
+		return nil, fmt.Errorf("statement is not type DDL: %T", mapped.Statement)
+	}
+
+	switch stmt.Action {
+	case sqlparser.DropStr:
+		return h.execDropTable(ctx, stmt)
+
+	default:
+		return nil, errors.Errorf("unsupported DDL action: %s", stmt.Action)
+	}
+}
+
+func (h *DDLHandler) execDropTable(ctx context.Context, stmt *sqlparser.DDL) (pproto.StreamClient, error) {
+	if n := len(stmt.FromTables); n != 1 {
+		return nil, fmt.Errorf("statement can only contain a single drop table, but got: %d", n)
+	}
+
+	indexName := stmt.FromTables[0].ToViewName().Name.String()
+	if err := h.api.DeleteIndex(ctx, indexName); err != nil {
+		return nil, errors.Wrapf(err, "deleting index %s", indexName)
+	}
+	return pproto.EmptyStream{}, nil
+}