Add drop(index:)

Author: jberkel

Sources/SQLite/Schema/SchemaChanger.swift

@@ -45,6 +45,7 @@ public class SchemaChanger: CustomStringConvertible {
         case addColumn(ColumnDefinition)
         case addIndex(IndexDefinition, ifNotExists: Bool)
         case dropColumn(String)
+        case dropIndex(String, ifExists: Bool)
         case renameColumn(String, String)
         case renameTable(String)
         case createTable(columns: [ColumnDefinition], ifNotExists: Bool)
@@ -60,6 +61,8 @@ public class SchemaChanger: CustomStringConvertible {
                 return "ALTER TABLE \(table.quote()) RENAME COLUMN \(from.quote()) TO \(to.quote())"
             case .dropColumn(let column) where SQLiteFeature.dropColumn.isSupported(by: version):
                 return "ALTER TABLE \(table.quote()) DROP COLUMN \(column.quote())"
+            case .dropIndex(let name, let ifExists):
+                return "DROP INDEX \(ifExists ? " IF EXISTS " : "") \(name.quote())"
             case .createTable(let columns, let ifNotExists):
                 return "CREATE TABLE \(ifNotExists ? " IF NOT EXISTS " : "") \(table.quote()) (" +
                     columns.map { $0.toSQL() }.joined(separator: ", ") +
@@ -111,6 +114,10 @@ public class SchemaChanger: CustomStringConvertible {
             operations.append(.dropColumn(column))
         }
 
+        public func drop(index: String, ifExists: Bool = false) {
+            operations.append(.dropIndex(index, ifExists: ifExists))
+        }
+
         public func rename(column: String, to: String) {
             operations.append(.renameColumn(column, to))
         }
@@ -324,8 +331,9 @@ extension TableDefinition {
     func apply(_ operation: SchemaChanger.Operation?) -> TableDefinition {
         switch operation {
         case .none: return self
-        case .createTable, .addIndex: fatalError()
+        case .createTable, .addIndex, .dropIndex: fatalError()
         case .addColumn: fatalError("Use 'ALTER TABLE ADD COLUMN (...)'")
+
         case .dropColumn(let column):
             return TableDefinition(name: name,
                 columns: columns.filter { $0.name != column },

Tests/SQLiteTests/Schema/SchemaChangerTests.swift

@@ -124,6 +124,44 @@ class SchemaChangerTests: SQLiteTestCase {
         }
     }
 
+    func test_drop_index() throws {
+        try db.execute("""
+            CREATE INDEX age_index ON users(age)
+        """)
+
+        try schemaChanger.alter(table: "users") { table in
+            table.drop(index: "age_index")
+        }
+        let indexes = try schema.indexDefinitions(table: "users").filter { !$0.isInternal }
+        XCTAssertEqual(0, indexes.count)
+    }
+
+    func test_drop_index_if_exists() throws {
+        try db.execute("""
+            CREATE INDEX age_index ON users(age)
+        """)
+
+        try schemaChanger.alter(table: "users") { table in
+            table.drop(index: "age_index")
+        }
+
+        try schemaChanger.alter(table: "users") { table in
+            table.drop(index: "age_index", ifExists: true)
+        }
+
+        XCTAssertThrowsError(
+            try schemaChanger.alter(table: "users") { table in
+                table.drop(index: "age_index", ifExists: false)
+            }
+        ) { error in
+            if case Result.error(let message, _, _) =  error {
+                XCTAssertEqual(message, "no such index: age_index")
+            } else {
+                XCTFail("unexpected error \(error)")
+            }
+        }
+    }
+
     func test_drop_table() throws {
         try schemaChanger.drop(table: "users")
         XCTAssertThrowsError(try db.scalar(users.count)) { error in