Definition
/**
* Create an index column specification from an expression.
*
* Use chainable methods: ->asc(), ->desc(), ->nullsFirst(), ->nullsLast(), ->opclass(), ->collate()
*
* Example: index_expr(fn_call('lower', col('email')))->desc()
*
* @param Expression $expression The expression to index
*/
index_expr(Expression $expression) : IndexColumn