fix(UPDATE): only perform subselect matching if necessary (#989)

the issue was that while calculating the `UPDATE.elements`, we
accidentially assumed that the calculated element would lead to a join,
hence we did our subselect matching. This logic is not necessary for non
`SELECT` queries --> there we need joins if we do a `SELECT * from
<entity with calculated element /w path expression>`

---

fix(`UPDATE`): no assocs in list which matches subquery results

db-service/lib/cqn4sql.js

@@ -134,7 +134,7 @@ function cqn4sql(originalQuery, model) {
         const primaryKey = { list: [] }
         for (const k of Object.keys(queryTarget.elements)) {
           const e = queryTarget.elements[k]
-          if (e.key === true && !e.virtual) {
+          if (e.key === true && !e.virtual && e.isAssociation !== true) {
             subquery.SELECT.columns.push({ ref: [e.name] })
             primaryKey.list.push({ ref: [transformedFrom.as, e.name] })
           }

db-service/lib/infer/index.js

@@ -963,7 +963,8 @@ function infer(originalQuery, model) {
           if (element.type !== 'cds.LargeBinary') {
             queryElements[k] = element
           }
-          if (isCalculatedOnRead(element)) {
+          // only relevant if we actually select the calculated element
+          if (originalQuery.SELECT && isCalculatedOnRead(element)) {
             linkCalculatedElement(element)
           }
         }

db-service/test/cqn4sql/UPDATE.test.js

@@ -200,4 +200,41 @@ describe('UPDATE with path expression', () => {
     let res = cqn4sql(u, model)
     expect(JSON.parse(JSON.stringify(res))).to.deep.equal(JSON.parse(JSON.stringify(expected)))
   })
+
+  it('path expression via calculated element leads to subquery if used in where', () => {
+    const q = UPDATE('bookshop.Orders.Items').set({ price: 5 }).where('price = 4.99')
+
+    const res = cqn4sql(q, model)
+
+    const expected = UPDATE.entity({ ref: ['bookshop.Orders.Items'] }).alias('Items2')
+    expected.UPDATE.where = [
+      {
+        list: [{ ref: ['Items2', 'up__ID'] }, { ref: ['Items2', 'book_ID'] }],
+      },
+      'in',
+      cds.ql`
+        (SELECT
+          Items.up__ID,
+          Items.book_ID
+        FROM bookshop.Orders.Items AS Items
+        LEFT JOIN bookshop.Books AS book ON book.ID = Items.book_ID
+        WHERE (book.stock * 2) = 4.99
+        )
+      `,
+    ]
+
+    expect(JSON.parse(JSON.stringify(res))).to.deep.equal(JSON.parse(JSON.stringify(expected)))
+  })
+
+  it('if there is no path expression in the where, we dont need subselect magic', () => {
+    const q = UPDATE('bookshop.Orders.Items').set({ quantity: 3 }).where('1 = 1')
+    const res = cqn4sql(q, model)
+    expect(JSON.parse(JSON.stringify(res))).to.eql({
+      UPDATE: {
+        entity: { ref: ['bookshop.Orders.Items'], as: 'Items' },
+        where: [{ val: 1 }, '=', { val: 1 }],
+      },
+    })
+    expect(res.UPDATE).to.have.property('data')
+  })
 })

db-service/test/cqn4sql/model/update.cds

@@ -15,6 +15,14 @@ entity Authors {
   alive  : Boolean;
 }
 
+entity Orders {
+  key ID: UUID;
+  Items: composition of many {
+    key book: Association to Books;
+    price: Decimal = book.stock * 2;
+  }
+}
+
 service CatalogService {
    @odata.draft.enabled
    entity Books as projection on bookshop.Books;