Use upsert statement when inserting to postgres state store

[sdil]

Summary

Warning

I'm not 100% sure if this implementation is accurate and produce the same result as previous one

When I was trying the Postgres state store, my test application was stuck after creating less than 10 actors. After figuring out the bottleneck, it seems like the DELETE statement is causing the PostgreSQL to be slow.

My initial thought is, DELETE statement is there to ensure that there's only 1 row for each actor exists in the database. Please correct me if I'm wrong.

I swapped the DELETE SQL statement to use INSERT .... ON CONFLICT SQL. Unfortunately, Squirrel does not support "ON CONFLUCT" statement correctly (refer Masterminds/squirrel#83 (comment)) so I have to use .Suffix method to manually construct the statement.

After changing this implementation, my test application was running fine creating 1,000 actors

[Tochemey]

@sdil you are correct. The DELETE/INSERT pattern is to do what ON CONFLICT is doing. I am chocked it slows down the application. However, I do know about the suffix option of squirrel. Thanks for the PR I will take a look shortly.

[Tochemey]

@sdil I left some few comments.