From de86cf889d350a55fb271c4eedbf2873c2392dd3 Mon Sep 17 00:00:00 2001
From: fulldump <gerardooscarjt@gmail.com>
Date: Wed, 25 Jan 2023 02:02:18 +0100
Subject: [PATCH] feat: optimize patch, do not persist if diff is empty

---
 collection/collection.go      |  4 ++++
 collection/collection_test.go | 37 +++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/collection/collection.go b/collection/collection.go
index a9625df..00fe550 100644
--- a/collection/collection.go
+++ b/collection/collection.go
@@ -415,6 +415,10 @@ func (c *Collection) patchByRow(row *Row, patch interface{}, persist bool) error
 		return fmt.Errorf("cannot diff: %w", err)
 	}
 
+	if len(diff) == 2 { // diff == '{}'
+		return nil
+	}
+
 	// index update
 	err = indexRemove(c.Indexes, row)
 	if err != nil {
diff --git a/collection/collection_test.go b/collection/collection_test.go
index 7afeb8b..d1677b9 100644
--- a/collection/collection_test.go
+++ b/collection/collection_test.go
@@ -4,7 +4,9 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"io/ioutil"
+	"os"
 	"strconv"
 	"sync"
 	"testing"
@@ -346,6 +348,41 @@ func TestPersistenceUpdate(t *testing.T) {
 	})
 }
 
+func TestPersistenceUpdate_TwiceOptimization(t *testing.T) {
+	Environment(func(filename string) {
+
+		// Setup
+		c, _ := OpenCollection(filename)
+		c.Index("my-index", &IndexMapOptions{
+			Field: "id",
+		})
+		row, _ := c.Insert(map[string]interface{}{"id": "1", "name": "Pablo"})
+
+		// Run
+		for i := 0; i < 10; i++ {
+			c.Patch(row, map[string]interface{}{"name": "Jaime"})
+		}
+		c.Close()
+
+		// Check
+		numPatchCommands := 0
+		f, _ := os.Open(filename)
+		d := json.NewDecoder(f)
+		for {
+			c := Command{}
+			if decodeErr := d.Decode(&c); decodeErr == io.EOF {
+				break
+			}
+
+			if c.Name == "patch" {
+				numPatchCommands++
+			}
+		}
+
+		AssertEqual(numPatchCommands, 1)
+	})
+}
+
 type MockIndex struct {
 	AddRowCallback    func(row *Row) error
 	RemoveRowCallback func(row *Row) error