Performance Issue in Edge Creation for Large Tables and Index Creation

### Questions:
1. How can I create index for graph tables?
2. How effective are they? I am using a gin index right now on properties, and I can see that the performance does improve for the initial 200k edge creations, but the performance starts to degrade severely after that, does creating indexes on specifically the key that I am using in the MATCH clause of my edge creation query help?
3. I have also tried to skip to the 200k offset and start my edge creations from this point, but the performance is still poor for the rows after the 200k mark onwards, does this mean there is a limitation to indexes? How can I insert 8 million edges to my table within a reasonable time period?

### What we have tried:
#### Question 1
I have referred to Issue https://github.com/apache/age/issues/2137 to create btree and gin indexes, so far only this works for me:

```
# worked and query plan shows that we are using the index, but is slow after >200k edge creations
CREATE INDEX index_name ON schema_name."table_name" USING gin (properties);

# worked but query plan shows that we are using Seq Scan
CREATE INDEX IF NOT EXISTS index_name ON schema_name."table_name" USING gin ((properties -> '"tableId"'));

# worked but query plan shows us we are using Seq Scan
CREATE INDEX index_name ON schema_name."table_name" USING btree ((properties->>'"tableId"'));

```

and the following returns syntax errors:

```
# trying to create gin index on more specific key within properties that I am using in the MATCH clause for edge creation query
# got error -> ERROR: operator does not exist: ag_catalog.agtype -> unknown

CREATE INDEX IF NOT EXISTS index_name
ON schema_name."table_name" USING gin ((properties -> 'some_id'));

# trying to create btree index in general
# got error -> ERROR: type "agtype" does not exist

CREATE INDEX idx_btree_name
ON test."NodeType1"
USING btree (agtype_access_operator(VARIADIC ARRAY[properties, '"name"'::agtype]));

# got server crash/disconnections in pgadmin

CREATE INDEX IF NOT EXISTS idx_user_id ON goodreads_graph."User" USING BTREE (id);

```

---

#### Question 2 & 3
Our query looks something like this:
```
SELECT * FROM cypher('schema_name', $$
WITH {cypher_array} AS rows
UNWIND rows AS row
MATCH (a:Person {PersonId: row.StartId}),
(b:Person {PersonId: row.EndId})
CREATE (a)-[e:{edge_name} {{
StartId: row.StartId,
EndId: row.EndId,
otherprops: row.other_props
}}]->(b)
$$) AS (e agtype);
```

and we are doing one insertion for every 100 rows, for an offset of 100k rows from the original graph table that has 8 million rows. Initially it would take under 2-3s for every 100 rows, but starting from the 200k offset, the time would increase up to 100 - 1000s for every 100 rows.

The query plan tells me it seems to be using the index I've created `Bitmap Index Scan on idx_something...`, and I am at a loss as to what other things I can try to improve the performance of the edge creation queries.

If you could help us understand this, it would be a great help, thank you!