PoC: Extend Map capabilities

[BobdenOs]

‼️EXPERIMENTAL‼️

Don't expect any of these features to every be actually be released !!!

Examples

A list of implemented and tested Map queries.

// allows simple path expression on Map type columns
SELECT map.a as extract FROM map;
SELECT map.a.b as extract FROM map;

// allows extracting paths through array values
SELECT map.a.b.![*].d as extract FROM map;

// allows filtering on array values before extracting further
SELECT map.a.b.![*][d != null].d as extract FROM map;

// allows selecting from Map values as path expression
SELECT c:Boolean, d:Boolean FROM map:map.a.b

// allows using Map path expressions inside WHERE clauses
SELECT map as extract FROM map WHERE map.a.b != null;
SELECT c:Boolean, d:Boolean FROM ${map}:map.a.b WHERE d != null

// allows selecting from Map values including infix filters
SELECT c:Boolean, d:Boolean FROM ${map}:map.a.b.![*][c != null]

As * is a special character it has to be escaped conincidentially as cds uses ![...] as the escape syntax it creates a very similar syntax as classic JSON path definitions use ![*]. The main difference being the ! which does appropriately points out how crazy of an operation is being used.