wip

node.go

@@ -57,7 +57,8 @@ type Node struct {
 	Markdown         bool
 }
 
-func NodeTree(userID int, synced uint64) (nodes []TreeNode, maxSeq uint64, err error) { // {{{
+func NodeTree(userID, offset int, synced uint64) (nodes []TreeNode, maxSeq uint64, moreRowsExist bool, err error) { // {{{
+	const LIMIT = 8
 	var rows *sqlx.Rows
 	rows, err = db.Queryx(`
 		SELECT
@@ -74,14 +75,17 @@ func NodeTree(userID int, synced uint64) (nodes []TreeNode, maxSeq uint64, err e
 			public.node
 		WHERE
 			user_id = $1 AND (
-				created_seq > $2 OR
-				updated_seq > $2 OR
-				deleted_seq > $2
+				created_seq > $4 OR
+				updated_seq > $4 OR
+				deleted_seq > $4
 			)
 		ORDER BY
 			created ASC
+		LIMIT $2 OFFSET $3
 		`,
 		userID,
+		LIMIT + 1,
+		offset,
 		synced,
 	)
 	if err != nil {
@@ -95,12 +99,24 @@ func NodeTree(userID int, synced uint64) (nodes []TreeNode, maxSeq uint64, err e
 	}
 
 	nodes = []TreeNode{}
+	numNodes := 0
 	for rows.Next() {
+		// Query selects up to one more row than the decided limit.
+		// Saves one SQL query for row counting.
+		// Thus if numNodes is larger than the limit, more rows exist for the next call.
+		numNodes++
+		if numNodes > LIMIT {
+			moreRowsExist = true
+			return
+		}
+
 		node := TreeNode{}
 		if err = rows.StructScan(&node); err != nil {
 			return
 		}
 		nodes = append(nodes, node)
+
+		// DeletedSeq will be 0 if invalid, and thus not be a problem for the max function.
 		maxSeq = max(maxSeq, node.CreatedSeq, node.UpdatedSeq, uint64(node.DeletedSeq.Int64))
 	}