From c22eea13adab71a48694ca276183809977aef892 Mon Sep 17 00:00:00 2001
From: Ben Johnson <benbjohnson@yahoo.com>
Date: Tue, 5 Jan 2021 14:07:17 -0700
Subject: [PATCH] Add checkpoint tests

---
 db.go      | 19 +++++++++---------
 db_test.go | 59 ++++++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 62 insertions(+), 16 deletions(-)

diff --git a/db.go b/db.go
index c08f541..8e248b5 100644
--- a/db.go
+++ b/db.go
@@ -34,13 +34,12 @@ const (
 
 // DB represents a managed instance of a SQLite database in the file system.
 type DB struct {
-	mu               sync.RWMutex
-	path             string        // part to database
-	db               *sql.DB       // target database
-	rtx              *sql.Tx       // long running read transaction
-	pageSize         int           // page size, in bytes
-	notify           chan struct{} // closes on WAL change
-	lastCheckpointAt time.Time     // last checkpoint time
+	mu       sync.RWMutex
+	path     string        // part to database
+	db       *sql.DB       // target database
+	rtx      *sql.Tx       // long running read transaction
+	pageSize int           // page size, in bytes
+	notify   chan struct{} // closes on WAL change
 
 	ctx    context.Context
 	cancel func()
@@ -682,7 +681,7 @@ func (db *DB) Sync() (err error) {
 		checkpoint = true
 	} else if db.MaxCheckpointPageN > 0 && newWALSize >= calcWALSize(db.pageSize, db.MaxCheckpointPageN) {
 		checkpoint, checkpointMode = true, CheckpointModeRestart
-	} else if db.CheckpointInterval > 0 && !db.lastCheckpointAt.IsZero() && time.Since(db.lastCheckpointAt) > db.CheckpointInterval && newWALSize > calcWALSize(db.pageSize, 1) {
+	} else if db.CheckpointInterval > 0 && !info.dbModTime.IsZero() && time.Since(info.dbModTime) > db.CheckpointInterval && newWALSize > calcWALSize(db.pageSize, 1) {
 		checkpoint = true
 	}
 
@@ -750,6 +749,7 @@ func (db *DB) verify() (info syncInfo, err error) {
 	if fi, err := os.Stat(db.Path()); err != nil {
 		return info, err
 	} else {
+		info.dbModTime = fi.ModTime()
 		db.dbSizeGauge.Set(float64(fi.Size()))
 	}
 
@@ -826,6 +826,7 @@ func (db *DB) verify() (info syncInfo, err error) {
 
 type syncInfo struct {
 	generation    string    // generation name
+	dbModTime     time.Time // last modified date of real DB file
 	walSize       int64     // size of real WAL file
 	walModTime    time.Time // last modified date of real WAL file
 	shadowWALPath string    // name of last shadow WAL file
@@ -1166,8 +1167,6 @@ func (db *DB) checkpoint(mode string) (err error) {
 		return fmt.Errorf("release read lock: %w", err)
 	}
 
-	db.lastCheckpointAt = time.Now()
-
 	return nil
 }
 
diff --git a/db_test.go b/db_test.go
index 688c413..8d50179 100644
--- a/db_test.go
+++ b/db_test.go
@@ -519,17 +519,64 @@ func TestDB_Sync(t *testing.T) {
 
 	// Ensure DB checkpoints after minimum number of pages.
 	t.Run("MinCheckpointPageN", func(t *testing.T) {
-		t.Skip()
-	})
+		db, sqldb := MustOpenDBs(t)
+		defer MustCloseDBs(t, db, sqldb)
 
-	// Ensure DB forces checkpoint after maximum number of pages.
-	t.Run("MaxCheckpointPageN", func(t *testing.T) {
-		t.Skip()
+		// Execute a query to force a write to the WAL and then sync.
+		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
+			t.Fatal(err)
+		} else if err := db.Sync(); err != nil {
+			t.Fatal(err)
+		}
+
+		// Write at least minimum number of pages to trigger rollover.
+		for i := 0; i < db.MinCheckpointPageN; i++ {
+			if _, err := sqldb.Exec(`INSERT INTO foo (bar) VALUES ('baz');`); err != nil {
+				t.Fatal(err)
+			}
+		}
+
+		// Sync to shadow WAL.
+		if err := db.Sync(); err != nil {
+			t.Fatal(err)
+		}
+
+		// Ensure position is now on the second index.
+		if pos, err := db.Pos(); err != nil {
+			t.Fatal(err)
+		} else if got, want := pos.Index, 1; got != want {
+			t.Fatalf("Index=%v, want %v", got, want)
+		}
 	})
 
 	// Ensure DB checkpoints after interval.
 	t.Run("CheckpointInterval", func(t *testing.T) {
-		t.Skip()
+		db, sqldb := MustOpenDBs(t)
+		defer MustCloseDBs(t, db, sqldb)
+
+		// Execute a query to force a write to the WAL and then sync.
+		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
+			t.Fatal(err)
+		} else if err := db.Sync(); err != nil {
+			t.Fatal(err)
+		}
+
+		// Reduce checkpoint interval to ensure a rollover is triggered.
+		db.CheckpointInterval = 1 * time.Nanosecond
+
+		// Write to WAL & sync.
+		if _, err := sqldb.Exec(`INSERT INTO foo (bar) VALUES ('baz');`); err != nil {
+			t.Fatal(err)
+		} else if err := db.Sync(); err != nil {
+			t.Fatal(err)
+		}
+
+		// Ensure position is now on the second index.
+		if pos, err := db.Pos(); err != nil {
+			t.Fatal(err)
+		} else if got, want := pos.Index, 1; got != want {
+			t.Fatalf("Index=%v, want %v", got, want)
+		}
 	})
 }