Fix statement_timeout interrupting most queries

ext/sqlite3/database.c

@@ -417,8 +417,10 @@ rb_sqlite3_statement_timeout(void *context)
     clock_gettime(CLOCK_MONOTONIC, &currentTime);
 
     if (!timespecisset(&ctx->stmt_deadline)) {
-        // Set stmt_deadline if not already set
-        ctx->stmt_deadline = currentTime;
+        struct timespec timeout;
+        timeout.tv_sec = ctx->stmt_timeout / 1000;
+        timeout.tv_nsec = (ctx->stmt_timeout % 1000) * 1000000L;
+        timespecadd(&currentTime, &timeout, &ctx->stmt_deadline);
     } else if (timespecafter(&currentTime, &ctx->stmt_deadline)) {
         return 1;
     }

ext/sqlite3/timespec.h

@@ -15,6 +15,15 @@
 			(vsp)->tv_nsec += 1000000000L;			\
 		}							\
 	} while (0)
+#define	timespecadd(tsp, usp, vsp)					\
+	do {								\
+		(vsp)->tv_sec = (tsp)->tv_sec + (usp)->tv_sec;		\
+		(vsp)->tv_nsec = (tsp)->tv_nsec + (usp)->tv_nsec;	\
+		if ((vsp)->tv_nsec >= 1000000000L) {			\
+			(vsp)->tv_sec++;				\
+			(vsp)->tv_nsec -= 1000000000L;			\
+		}							\
+	} while (0)
 #define timespecafter(tsp, usp)						\
 	(((tsp)->tv_sec > (usp)->tv_sec) ||				\
 	 ((tsp)->tv_sec == (usp)->tv_sec && (tsp)->tv_nsec > (usp)->tv_nsec))

test/test_integration_statement.rb

@@ -205,6 +205,16 @@ def test_long_running_statements_get_interrupted_when_statement_timeout_set
         SELECT i FROM r ORDER BY i LIMIT 1;
       SQL
     end
+
+    # (regression) Ensure queries that finish within the timeout complete,
+    # even ones running many instructions (time is instructions-based, not wall call)
+    @db.statement_timeout = 1_000
+    result = @db.execute <<~SQL
+      WITH RECURSIVE r(i) AS (VALUES(0) UNION ALL SELECT i+1 FROM r LIMIT 100000)
+      SELECT count(i) FROM r;
+    SQL
+    assert_equal 100_000, result.first.first
+  ensure
     @db.statement_timeout = 0
   end
 end