Postgres source: added items for array data type

[sashaNeshcheret]

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[sashaNeshcheret]

/test connector=connectors/source-postgres

🕑 connectors/source-postgres https://github.com/airbytehq/airbyte/actions/runs/2776068836
❌ connectors/source-postgres https://github.com/airbytehq/airbyte/actions/runs/2776068836
🐛 https://gradle.com/s/tuoytmtgml5zi

Build Failed

Test summary info:

Could not find result summary

[cgardens]

why do we have a constant for an array that contains items of a certain type?

[sashaNeshcheret]

Because previously we just have Array without items and it was the reason of failing during refresh schema. Currently throwing exception in such case was changed to logging error message and we are adding items to array on source side.

[cgardens]

Sorry. This really doesn't make sense to me. It seems like for Postgres that we are making the assumption that all arrays will be string arrays. That is not how postgres works. The docs say other types are supported. This is just going to break.

@grishick

[sashaNeshcheret]

/test connector=connectors/source-postgres

🕑 connectors/source-postgres https://github.com/airbytehq/airbyte/actions/runs/2781466960
✅ connectors/source-postgres https://github.com/airbytehq/airbyte/actions/runs/2781466960
No Python unittests run

Build Passed

Test summary info:

All Passed

[ryankfu]

Unless my context is incorrect, the issue is that for JsonSchemaType.ARRAY there should be a corresponding field items that indicates the type of information in the array: https://cswr.github.io/JsonSchema/spec/arrays/

What this solution seems to implement is a limited scope of only having the items be only of type strings which as Charles has mentioned is not the only datatype that postgres arrays can support. Feel free to correct me if the understanding isn't clear but having the context included in the PR body would be helpful for everyone to get up to speed

Furthermore, since this is a change in the current behavior it would seem that a good practice is to add a regression test that covers the scenario where items field is not defined for array datatypes and also tests that validates the various datatypes that postgres arrays supports. How can we help make sure you're unblocked on this issue?

[sashaNeshcheret]

@ryankfu, @cgardens you are right, solution that implemented in this PR was just for handling on-call issue and has limitation about types of items as possible quick solution. As far as on-call issue was fixed by PR and this approach has concerns, we can finish with temporal solution and discuss long term approach.
We investigated issue internally with team and for first point of view we have two several solution.
First solution is revert PR and leave as is, so we will use just JsonSchemaType.ARRAY without items and their types.
Another way is extend JDBCType(that just have java.sql.ARRAY type) with new types ARRAY_INT, ARRAY_TEXT etc, but seems we can just do it with copy paste JDBCType. With created PostgresJDBCType we can specify correct data type for array items. Something similar we have for MySqlSourceOperations that does not extend JdbcSourceOperations as all jdbc related sources, but implements SourceOperations with own MysqlType, but it require a lot of refactoring and testing.
@grishick @edgao @tuliren

CC: @alexandr-shegeda @VitaliiMaltsev

[cgardens]

closing as stale. feel free to re-open if this is something we are still working on.