mendix-odata-pushdown

Pushing OData query options into your own SQL

The problem this exists for

Mendix will publish any entity over OData, including one with no table behind it: declare the resource non-persistable, give it a read microflow, done. What the documentation does not say is that Mendix then applies none of the query options to your answer. $filter, $orderby, $top, $skip, $count and the key lookup all arrive on the request URI and all stay there. Whatever the microflow returns is exactly what the client gets.

That is not a 500 and not an empty grid. It is a 200 with the wrong rows:

• ?$top=5 returns all 917 rows and the widget shows five of them, so paging looks correct while every page ships the whole table.
• A client re-reading one held row by key gets the collection back, adopts the first row as that object's identity, and keeps it. A detail page for one record shows another record's data, and nothing logs a word.

The second one is the reason to care. It is not a performance problem; it is wrong data on screen, and every check is green.

What the pack gives you

Four Java actions and the entity they return. Nothing in them is specific to any database or any app.

{{MODULE}}.Parse(Uri, Columns, Dialect, MaxTop, DefaultTop,
                 DefaultOrderBy, KeyField, RejectUnsupported) -> {{MODULE}}.Query
{{MODULE}}.Key(Uri, KeyField)                                 -> String
{{MODULE}}.FilterNumber(Uri, Field, Fallback)                 -> Long
{{MODULE}}.CallStatement(Routine, Kind, Parameters, Dialect)  -> String

Parse is the whole thing. Key and FilterNumber are short forms for the common case — a resource reachable one way only ("the sessions of this weekend"), whose entire contract is one value out of $filter. CallStatement builds the invocation for a resource backed by a stored routine.

{{MODULE}}.Query

Field	Style	What it is
FilterSql	splice	" WHERE …", or empty
OrderBySql	splice	" ORDER BY … LIMIT n OFFSET m"
SelectSql	splice	" a, b, c" for $select, or empty for all columns
SelectedColumns	bind	the same columns as exposed names
Key	bind	the key the client is re-reading one row by; empty for a collection
Top, Skip	bind	the page, already clamped to MaxTop
SortColumn1/2, SortDirection1/2	bind	the sort, as exposed names and A/D
WantsCount	both	$count=true — the client wants the size of the set
Rejected, RejectReason	bind	the request asked for something untranslatable. Only a bind caller sees these: with RejectUnsupported = true (what a splice caller passes) Parse throws instead of returning, so a splice caller always has Rejected = false