Moved from GitHub dgraph/5017
Posted by emile-tawfik:
The issue
In v1.1.x with introduction of single relations, the only way to overwrite a single relation was to use multiple mutation in single transaction (delete + insert) (Allow node reference replacements on 1-to-1 relationships · Issue #4136 · dgraph-io/dgraph · GitHub).
However, it seems this method doesn’t work anymore since v1.2.2 because of a bug.
What version of Dgraph are you using?
The issue exists on v1.2.2 and master.
The issue doesn’t exist on v1.2.1
Steps to reproduce the issue (command/config used to run Dgraph).
There is a test I wrote to reproduce the issue. I added it in query/query4_test.go.
func TestOverwriteOneToOneRelationInATransaction(t *testing.T) {
schema := `
onetoonerel: uid .
data: int .
`
setSchema(schema)
triples := `
_:node1 <onetoonerel> _:node2 .
_:node2 <data> "42" .
`
resp, err := client.NewTxn().Mutate(context.Background(), &api.Mutation{
SetNquads: []byte(triples),
CommitNow: true,
})
require.NoError(t, err)
node1Uid := resp.Uids["node1"]
node2Uid := resp.Uids["node2"]
txn := client.NewTxn()
_, err = txn.Mutate(context.Background(), &api.Mutation{
DelNquads: []byte(fmt.Sprintf("<%s> <onetoonerel> <%s> .", node1Uid, node2Uid)),
})
require.NoError(t, err)
resp, err = txn.Mutate(context.Background(), &api.Mutation{
SetNquads: []byte(fmt.Sprintf(`<%s> <onetoonerel> _:node3 .
_:node3 <data> "24" .`, node1Uid)),
})
require.NoError(t, err)
node3Uid := resp.Uids["node3"]
err = txn.Commit(context.Background())
require.NoError(t, err)
query := fmt.Sprintf(`{
me(func:uid(%s)) {
uid
onetoonerel {
uid
}
}
}`, node1Uid)
js := processQueryNoErr(t, query)
require.JSONEq(t, fmt.Sprintf(`
{
"data": {
"me": [
{
"uid": "%s",
"onetoonerel": {
"uid": "%s"
}
}
]
}
}
`, node1Uid, node3Uid), js)
}
Expected behaviour and actual result.
After a bisect it seems that the bug was introduced in Overwrite values for uid predicates (#4883) · dgraph-io/dgraph@cc495fc · GitHub
Expected the test to pass.
Got:
--- FAIL: TestOverwriteOneToOneRelationInATransaction (1.07s)
query4_test.go:1596:
Error Trace: query4_test.go:1596
Error: Not equal:
expected: map[string]interface {}{"data":map[string]interface {}{"me":[]interface {}{map[string]interface {}{"onetoonerel":map[string]interface {}{"uid":"0x186bf"}, "uid":"0x186bd"}}}}
actual : map[string]interface {}{"data":map[string]interface {}{"me":[]interface {}{map[string]interface {}{"onetoonerel":map[string]interface {}{"uid":[]interface {}{"0x186be", "0x186bf"}}, "uid":"0x186bd"}}}}
Diff:
--- Expected
+++ Actual
@@ -5,3 +5,6 @@
(string) (len=11) "onetoonerel": (map[string]interface {}) (len=1) {
- (string) (len=3) "uid": (string) (len=7) "0x186bf"
+ (string) (len=3) "uid": ([]interface {}) (len=2) {
+ (string) (len=7) "0x186be",
+ (string) (len=7) "0x186bf"
+ }
},
Test: TestOverwriteOneToOneRelationInATransaction