Add Diff() function

This adds a Diff() function for generating a database diff to the
Connection object.

Author: MKleusberg

README.md

@@ -20,7 +20,6 @@ A Go library for accessing and using SQLite databases stored remotely on DBHub.i
 * Download a complete database
 * Upload a complete database
 * Retrieve database commit history details (size, branch, commit list, whatever else is useful)
-* Diffs between database revisions
 
 ### Requirements
 
@@ -81,5 +80,6 @@ Query results (JSON):
 * [List views](https://github.com/sqlitebrowser/go-dbhub/blob/master/examples/list_views/main.go) - List the views present in a database
 * [List indexes](https://github.com/sqlitebrowser/go-dbhub/blob/master/examples/list_indexes/main.go) - List the indexes present in a database
 * [Retrieve column details](https://github.com/sqlitebrowser/go-dbhub/blob/master/examples/column_details/main.go) - Retrieve the details of columns in a table
-  
+* [Generate diff between two revisions](https://github.com/sqlitebrowser/go-dbhub/blob/master/examples/diff_commits/main.go) - Figure out the differences between two databases or two versions of one database
+
 Please try it out, submits PRs to extend or fix things, and report any weirdness or bugs you encounter. :smile:

dbhub.go

@@ -49,6 +49,32 @@ func (c Connection) Columns(dbowner, dbname, table string) (columns []com.APIJSO
 	return
 }
 
+// Diff returns the differences between two commits of two databases, or if the details on the second database are left empty,
+// between two commits of the same database. You can also specify the merge strategy used for the generated SQL statements.
+func (c Connection) Diff(dbOwnerA string, dbNameA string, commitA string, dbOwnerB string, dbNameB string, commitB string, merge MergeStrategy) (diffs com.Diffs, err error) {
+	// Prepare the API parameters
+	data := url.Values{}
+	data.Set("apikey", c.APIKey)
+	data.Set("dbowner_a", dbOwnerA)
+	data.Set("dbname_a", dbNameA)
+	data.Set("commit_a", commitA)
+	data.Set("dbowner_b", dbOwnerB)
+	data.Set("dbname_b", dbNameB)
+	data.Set("commit_b", commitB)
+	if merge == PreservePkMerge {
+		data.Set("merge", "preserve_pk")
+	} else if merge == NewPkMerge {
+		data.Set("merge", "new_pk")
+	} else {
+		data.Set("merge", "none")
+	}
+
+	// Fetch the diffs
+	queryUrl := c.Server + "/v1/diff"
+	err = sendRequest(queryUrl, data, &diffs)
+	return
+}
+
 // Indexes returns the list of indexes present in the database, along with the table they belong to
 func (c Connection) Indexes(dbowner, dbname string) (idx map[string]string, err error) {
 	// Prepare the API parameters

examples/diff_commits/main.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/sqlitebrowser/go-dbhub"
+)
+
+func main() {
+	// Create a new DBHub.io API object
+	db, err := dbhub.New("YOUR_API_KEY_HERE")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Retrieve the differences between two commmits of the same database
+	user := "justinclift"
+	database := "DB4S download stats.sqlite"
+	commit1 := "34cbeebfc347a09406707f4220cd40f60778692523d2e7d227ccd92f4125c9ea"
+	commit2 := "bc6a07955811d86db79e9b4f7fdc3cb2360d40da793066510d792588a8bf8de2"
+	mergeMode := dbhub.PreservePkMerge
+	diffs, err := db.Diff(user, database, commit1, "", "", commit2, mergeMode)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Display the SQL statements needed to turn the first version of the database into the second.
+	// This should produce a similar output to the sqldiff utility.
+	fmt.Printf("SQL statements for turning the first version into the second:\n")
+	for _, i := range diffs.Diff { // There is one item for each modified database object
+		// Print schema changes to this object if there are any
+		if i.Schema != nil {
+			fmt.Printf("%s\n", i.Schema.Sql)
+		}
+
+		// Loop over all data changes in this object if there are any
+		for _, j := range i.Data {
+			fmt.Printf("%s\n", j.Sql)
+		}
+	}
+	fmt.Println()
+}

go.mod

@@ -10,4 +10,4 @@ replace (
 	github.com/Sirupsen/logrus v1.6.0 => github.com/sirupsen/logrus v1.6.0
 )
 
-require github.com/sqlitebrowser/dbhub.io v0.0.6
+require github.com/sqlitebrowser/dbhub.io v0.0.7

go.sum

@@ -125,6 +125,8 @@ github.com/sqlitebrowser/blackfriday v9.0.0+incompatible h1:ddH/UyzasooYgGIblVU4
 github.com/sqlitebrowser/blackfriday v9.0.0+incompatible/go.mod h1:/zga9sqpWzcewuI83AO5JZwe9+6F9GgPDdqqdNNEL/0=
 github.com/sqlitebrowser/dbhub.io v0.0.6 h1:hvIXQg0F/YDPFZEBeIGTtEBS9F3N02rYiEMtn98553c=
 github.com/sqlitebrowser/dbhub.io v0.0.6/go.mod h1:GgZi8wkjdRGkkUVgYNuZp5i+Yps3jGt/jjRuLKRi6Po=
+github.com/sqlitebrowser/dbhub.io v0.0.7 h1:1DrKD5BR5FjOwMg4NDet/a8b73HVLYmjxIR7S6ieaGU=
+github.com/sqlitebrowser/dbhub.io v0.0.7/go.mod h1:GgZi8wkjdRGkkUVgYNuZp5i+Yps3jGt/jjRuLKRi6Po=
 github.com/sqlitebrowser/github_flavored_markdown v0.0.0-20190120045821-b8cf8f054e47 h1:s0+Ea95n1LrsKh6rtclU/9Qb2/5ofvnfnR7gDDiFTw8=
 github.com/sqlitebrowser/github_flavored_markdown v0.0.0-20190120045821-b8cf8f054e47/go.mod h1:8vPIKi5FslxCXEgfQxrFtWfdclGy6VWAc9NA1ZTYCJg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

types.go

@@ -15,3 +15,21 @@ type ResultRow struct {
 type Results struct {
 	Rows []ResultRow
 }
+
+// MergeStrategy specifies the type of SQL statements included in the diff results.
+// The SQL statements can be used for merging databases and depending on whether and
+// how you want to merge you should choose your merge strategy.
+type MergeStrategy int
+
+const (
+	// NoMerge removes any SQL statements for merging from the diff results
+	NoMerge MergeStrategy = iota
+
+	// PreservePkMerge produces SQL statements which preserve the values of the primary key columns.
+	// Executing these statements on the first database produces a database similar to the second.
+	PreservePkMerge
+
+	// NewPkMerge produces SQL statements which generate new values for the primary key columns when
+	// executed. This avoids a couple of possible conflicts and allows merging more distant databases.
+	NewPkMerge
+)