feat(search): enable deep search with path expressions

[patricebender]

support search via path expressions:

• deep search via associations
• include calculated elements if explicitly requested

---

with cds.infer being a part of all our query objects, each query comes with target and elements even without the infer function of the db-servicebeing called. Hence, it was possible to calculate the search term as a very first step of cqn4sql. After the contains(…) function has been added to the queries where or having clause the usual join tree algorithm is executed, making it possible to use path expressions within the search term.

---

rework of #252

[johannes-vogel]

don't you need to append the search terms instead of replacing the existing where/having clauses?

[patricebender]

This is done in line 243ff

[patricebender]

blocked by cap/issues/issues/16172 → cds.infer can't handle table aliases:

> q = SELECT`from ${Books} as Foo { Foo.ID }`
Query {
  SELECT: {
    from: { ref: [ 'my.bookshop.Books' ], as: 'Foo' },
    columns: [ { ref: [ 'Foo', 'ID' ] } ]
  }
}
> q.elements
Uncaught:
Error: Couldn't resolve element "Foo/ID" in entity my.bookshop.Books [ 'ID', 'title', 'stock' ]
    at /Users/patricebender/SAPDevelop/foo/node_modules/@sap/cds/lib/ql/infer.js:80:22
    at Array.forEach (<anonymous>)
    at Function.elements4 (/Users/patricebender/SAPDevelop/foo/node_modules/@sap/cds/lib/ql/infer.js:61:32)
    at get elements [as elements] (/Users/patricebender/SAPDevelop/foo/node_modules/@sap/cds/lib/ql/SELECT.js:157:53)

[johannes-vogel]

blocked by cap/issues/issues/16172 → cds.infer can't handle table aliases:

> q = SELECT`from ${Books} as Foo { Foo.ID }`
Query {
  SELECT: {
    from: { ref: [ 'my.bookshop.Books' ], as: 'Foo' },
    columns: [ { ref: [ 'Foo', 'ID' ] } ]
  }
}
> q.elements
Uncaught:
Error: Couldn't resolve element "Foo/ID" in entity my.bookshop.Books [ 'ID', 'title', 'stock' ]
    at /Users/patricebender/SAPDevelop/foo/node_modules/@sap/cds/lib/ql/infer.js:80:22
    at Array.forEach (<anonymous>)
    at Function.elements4 (/Users/patricebender/SAPDevelop/foo/node_modules/@sap/cds/lib/ql/infer.js:61:32)
    at get elements [as elements] (/Users/patricebender/SAPDevelop/foo/node_modules/@sap/cds/lib/ql/SELECT.js:157:53)

Why would cds.infer have to handle aliases? Where do they stem from?

[patricebender]

Why would cds.infer have to handle aliases?

If we want to support path expressions in a search annotation, we must attach the search function to the query before it is going through the join algorithm for processing. But for the calculation of the searchable columns, we need to know the target of the query, to find out which elements must be searched. Hence, I rely on cds.infer to do the work instead of doing it by myself. And by doing so,I dont attach the elements to the original query anymore. For an expand column, cqn4sql builds a subquery, attaches a table alias and transforms the query. cds.infer can't resolve the columns starting with an alias name anymore

Where do they stem from?

Each cqn4sql transformation assigns unique table aliases to the given query. All transformed columns will be absolutified → all refs are prepended with the unique table alias.
This also accounts for where exists subqueries, or correlated subqueries stemming from expand