ColumnExpression first/last index

[ADBond]

Type of PR

• BUG
• FEAT
• MAINT
• DOC

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This provides some tooling for a dialect-agnostic way to select the first or last element of an array column, usable for instance in a blocking rule. So instead of

block_on("first_names_arr[1]", "last_names_arr[-1]")

in duckdb, which you would need to rewrite for other backends, you could have

block_on(
    ColumnExpression("first_names_arr").access_extreme_array_element("first"),
    ColumnExpression("last_names_arr").access_extreme_array_element("last"),
)

which will work for any backend.

PR Checklist

• Added documentation for changes
• Added feature to example notebooks or tutorial (if appropriate)
• Added tests (if appropriate)
• Updated CHANGELOG.md (if appropriate)
• Made changes based off the latest version of Splink
• Run the linter
• Run the spellchecker (if appropriate)

[RobinL]

👍