confluentinc/ksql

Add an array_positions function.

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#9,158 opened on Jun 1, 2022

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 (0 comments) (0 reactions) (0 assignees)Java (5,739 stars) (1,048 forks)batch import
enhancementfix-it-weekgood first issuestreaming-engineuser-defined-functions

Description

Is your feature request related to a problem? Please describe. The existing FIELD function works on a varags array of input strings. It does not work on an array of strings.

E.g.

+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|KSQL_COL_0                                                                                                                                                                 |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|0                                                                                                                                                                          |

Describe the solution you'd like In the above example, it'd be nice to return 1 or better an array of the positions where the element is present in the array.

See array_positions from https://www.postgresql.org/docs/current/functions-array.html.

Additional context See a short Slack discussion here: https://confluentcommunity.slack.com/archives/C6UJNMY67/p1654021013224899

Contributor guide

Tech stack
javasql
Domain
database
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Javaksql codebaseSQL array functions
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
Examine the existing FIELD function implementation in ksql (likely in the function registry). Understand the current varargs approach and how to extend it to handle array inputs. Reference PostgreSQL's array positions documentation for expected behavior. Consider returning an array of positions instead of a single index. Look for similar array functions already implemented in the codebase to follow patterns.