Match multiple patterns (OPTIONAL MATCH)

[AlexPresso]

I'm trying to execute the following query:

func FindUserFusionNetwork(sess gogm.SessionV2, discordTag string) (fusions []structures.Fusion) {
	query := `MATCH (i:Item)-[fr:FUSION_INPUT|FUSION_RESULT]-(f:Fusion) ` +
		`OPTIONAL MATCH (u:User{discordUsername: $discordTag})-[ui:INVENTORY_ITEM]->(i) ` +
		`RETURN *`
	err = sess.Query(context.Background(), query, map[string]interface{}{"discordTag": discordTag}, &fusions)
        fmt.Println(err)
	return
}

While it works perfectly in the Neo4J Browser, gogm (v2) seems unable to extract the requested structure from the resultset.
Am I doing something wrong ?

Edit: It returns the following error: failed auto read tx, label not found for node [1281], gogm: internal error, but the node having id = 1281 is an Item node, shouldn't it hydrate the Fusion structure based on it ?.

[erictg]

Did you register Item when you initialized gogm? Also, gogm expects a slice of pointers. It looks like the slice of Fusion being passed in is a normal slice.

[AlexPresso]

Oh yes, you are right, I'm fixing the pointer, thanks.
Yes, Item and all needed structures are initialized at startup:

func Init() {
	config := gogm.Config{
		IndexStrategy: gogm.IGNORE_INDEX,
		PoolSize:      viper.GetInt("db.poolSize"),
		Port:          viper.GetInt("db.port"),
		Host:          viper.GetString("db.host"),
		Password:      viper.GetString("db.password"),
		Username:      viper.GetString("db.username"),
		Protocol:      "bolt",
	}

	_gogm, err := gogm.New(
		&config,
		gogm.DefaultPrimaryKeyStrategy,
		&structures.Item{},
		&structures.Fusion{},
		&structures.User{},
		&structures.InventoryItem{},
	)

	if err != nil {
		log.Fatal(err)
	}

	gogm.SetGlobalGogm(_gogm)
}

[erictg]

Did that fix the issue?

[AlexPresso]

No, it's still giving that error

[erictg]

I'm wondering if its getting confused with return *. I'm going to write a test to see if I can reproduce this and get back to you.

[lomoval]

@erictg should the current version of GOGM support queries that do not return paths (as in this issue)?
I thought it supports paths only and can also handle requests that return a node.

From my experience.
Without paths GOGM can processed queries that return just a node. Something like this:

MATCH (n)-[..]-(..) WHERE ... RETURN n

But when you need relations and nodes, you need to use paths.
From my code, such query doesn't work (same with RETURN *):

MATCH (object{twinId:"..."})-[r:IS_DESCRIBED_BY]->(value:ReferenceInformationObject{twinId:".."})
WHERE value.name in [...] RETURN object,r,value

But paths GOGM process correctly:

MATCH p=(object{twinId:"..."})-[r:IS_DESCRIBED_BY]->(value:ReferenceInformationObject{twinId:"..."})
WHERE value.name in [...] RETURN p

In my code, I always use paths for GOGM queries. Without returning paths, GOGM does not work.

[AlexPresso]

Yes, but that means you can only match one and only path per query, It's impossible to use OPTIONAL MATCH in a single path.
It's also the same when you want to use UNION.

[nikitawootten]

@AlexPresso you can use an OPTIONAL MATCH in a single path using the following syntax:

MATCH p=(n:SomeNode)-[..]-(..) WHERE ... RETURN p
UNION ALL OPTIONAL MATCH p=(n)-[..]-(..) RETURN p

[nikitawootten]

@AlexPresso I believe that the bug that spawned the original discussion behind this issue is also solved by some of the changes I made to the decoder in #82. We're close to merging it now, but could you let me know if this bug (failed auto read tx, label not found for node...) is solved by these changes?

[nikitawootten]

Please report back if the problem persists :)