Query interrupt support

Adds the ability to interrupt a database connection during a
long-running query.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Author: stephencelis

SQLite Tests/DatabaseTests.swift

@@ -264,6 +264,22 @@ class DatabaseTests: SQLiteTestCase {
         AssertSQL("INSERT INTO users (email, admin) VALUES ('alice@example.com', 1)", 2)
     }
 
+    func test_interrupt_interruptsLongRunningQuery() {
+        insertUsers(map("abcdefghijklmnopqrstuvwxyz") { String($0) })
+        db.create(function: "sleep") { args in
+            usleep(UInt32(Double(args[0] as? Double ?? Double(args[0] as? Int64 ?? 1)) * 1_000_000))
+            return nil
+        }
+
+        let stmt = db.prepare("SELECT *, sleep(?) FROM users", 0.1)
+        stmt.run()
+        XCTAssert(!stmt.failed)
+
+        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(10 * NSEC_PER_MSEC)), dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), db.interrupt)
+        stmt.run()
+        XCTAssert(stmt.failed)
+    }
+
     func test_userVersion_getsAndSetsUserVersion() {
         XCTAssertEqual(0, db.userVersion)
         db.userVersion = 1

SQLite Tests/TestHelper.swift

@@ -40,6 +40,10 @@ class SQLiteTestCase: XCTestCase {
     }
 
     func insertUsers(names: String...) {
+        insertUsers(names)
+    }
+
+    func insertUsers(names: [String]) {
         for name in names { insertUser(name) }
     }
 

SQLite/Database.swift

@@ -343,6 +343,11 @@ public final class Database {
         return run("ROLLBACK TO SAVEPOINT \(quote(literal: savepointName))")
     }
 
+    /// Interrupts any long-running queries.
+    public func interrupt() {
+        sqlite3_interrupt(handle)
+    }
+
     // MARK: - Configuration
 
     public var foreignKeys: Bool {

SQLite/Statement.swift

@@ -194,7 +194,7 @@ public final class Statement {
             self.status = block()
             if self.failed {
                 self.reason = String.fromCString(sqlite3_errmsg(self.database.handle))
-                assert(self.status == SQLITE_CONSTRAINT, "\(self.reason!)")
+                assert(self.status == SQLITE_CONSTRAINT || self.status == SQLITE_INTERRUPT, "\(self.reason!)")
             }
         }
     }