From `alpha-40` we've been using a `WHERE` clause to fetch required rows and generate mutation response. This has a few limitations like the requirement of a primary key/unique constraint. This also returns inconsistent data on `delete` mutation as mentioned in #1794.
Now, we're using `VALUES (..)` (refer [here](https://www.postgresql.org/docs/current/sql-values.html)) expression to form virtual table rows in `SQL` to generate mutation response.
Internal changes:-
- Not to use primary key/unique constraint columns:-
- Revert back to `ConstraintName` from `TableConstraint` in `TableInfo` type
- Remove `tcCols` field in `TableConstraint` type
- Modify `table_info.sql` and `fetchTableMeta` function `SQL`
- A test case to perform `delete` mutation and returning relational objects.
If returning field contains nested selections then mutation is performed in two steps
1. Mutation is performed with returning columns of any primary key and unique constraints
2. returning fields are queried on rows returned by selecting from table by filtering with column values returned in Step 1.
Since mutation takes two courses based on selecting relations in returning field, it is hard to maintain sequence of prepared arguments (PrepArg) generated while resolving returning field. So, we're using txtConverter instead of prepare to resolve mutation fields.
* remove phase one/two distinction and hdbquery typeclass
* move extensions to default-extensions
* switch to LazyTx which only acquires a connection if needed
* move defns from TH module into Ops module
* remove tojson orphan instance for http exception
* remove orphan instance for dmlp1
* getTopLevelNodes will not throw any exceptions
* improved nested insert execution logic
* integrate error path, improve executing 'withExp' and improve tests
* add more readable types in '/Resolve/Insert.hs'
* set conflict context just before executing WITH expression
Better SQL generation for select queries (the query plans will be the same but much more readable). This closes some long standing issues (#6, #121, #278).
Insert trigger function: If query affects no rows then return `null`
Insert trigger function is modified to have
`IF r IS NULL THEN RETURN null; ELSE RETURN r; END IF;` in return statement.
* fix primary key changing on upsert, fix#342
* add 'update_columns' in 'on_conflict' object, consider 'allowUpsert'
* 'ConflictCtx' type should respect upsert cases
* validation for not null fields in an object
* add 'on_conflict' condition to allow upsert mutation, closes#105
* check for empty unique or primary key constraints
* add 'on_conflict' condition test cases and introspection test case
* update 'conflict_action' enum values' description
