feat: EXPOSED-560 Support DISTINCT ON from Postgres

[obabichevjb]

Description

Added support for DISTINCT ON clauses in the Query class, enabling retrieval of distinct rows based on specified columns for SQL SELECT statements.

Detailed description:

• What: Introduced new methods withDistinctOn(Column<*>, vararg Column<*>) and withDistinctOn(Pair<Column<*>, SortOrder>, vararg Pair<Column<*>, SortOrder>) in the Query class to allow the use of DISTINCT ON clauses. These methods enable distinct rows selection based on the specified columns and optionally ordered by specified sort orders.
• Why: We had several requests for that feature from GitHub and Slack
• How: The changes were implemented by:
  • Adding two new methods to the Query class to set the distinctOn property.
  • Adjusting the prepareSQL method to include the DISTINCT ON clause when distinctOn is set.

---

Type of Change

• New feature

Affected databases:

• Postgres
• H2

---

Related Issues

EXPOSED-560 Support DISTINCT ON from Postgres
#500