Enhance integration test suite

[kparwal]

Add datatype conversion integration test suite and implementation for PostgreSQL.

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[henrymai]

Similar comment here as earlier about using .map() instead of .forEach() for these kinds of situations.

[kparwal]

not sure i understand the difference. rows in practice has just one value. turning it into a stream just to run map seems more roundabout.

[henrymai]

I don't feel strongly as to whether or not you should change this, which is why I approved the pull request in addition to leaving the comments before.

But if you're wondering about the reasoning:

Its a declarative vs imperative style (where declarative is preferred when possible).

More formally this (creating the list and then looping through it to add to it) is an antipattern called ITM (initialize then modify): https://www.youtube.com/watch?v=VV9vwFsaQ6U

In scala a .map() is always used for situations like this instead (just transforming one collection into another) vs a .foreach() which is meant for side effecting operations: https://stackoverflow.com/a/44042773

The youtube link above is mostly about c++ (although he has examples in python as well) and stackoverflow link is on scala, so its not a concept that is isolated to any single language.

It only seems roundabout because its not something that most Java developers are used to (unless they started with Java 8 and beyond), but this is also why they added all of this stuff to Java.

EDIT:

Also my original comment was about .map() vs .foreach() in general, I did not take into consideration that there was only a single element in the List, because a .foreach() was being used in the diff.

For the situations where one knows that the resulting List only comprises of a single or few elements, then one can just use List.of(<element>) instead of using a .foreach() or .map()

[henrymai]

Looks good to me other than the small comments on:

• map() instead forEach()
• Map.of() instead of Guava builder
• List.of() instead of the Guava's ImmutableList.of()