Querying "JSON properties"

[ralfhandl]

"JSON properties" are stream properties whose value is of media type application/json or one of its subtypes. They were introduced with ODATA-1177.

As outlined in OData Extension for JSON Data we need query capabilities on these properties.

Requirements:

1. Specify a JSON Schema that describes/restricts the JSON stream values (ODATA-1275)
2. Address parts of the JSON stream values in common expressions, e.g. in $filter, $compute, $orderby (this issue)

The second requirement can be solved via functions on JSON stream properties, e.g.

• extract/compute an OData value (primitive, complex, collection) from a JSON stream
• special case: extract/compute a JSON stream from a JSON stream
• special case: extract/compute a Boolean value from a JSON stream

These functions can be inspired by (or be direct wrappers for) the SQL/JSON functions

• JSON_QUERY, see IBM Db2, Microsoft SQL Server, Google BigQuery Standard SQL, or SAP HANA
• JSON_VALUE, see IBM Db2, Microsoft SQL Server, Google BigQuery Standard SQL, or SAP HANA

PostgreSQL has its own set of JSON Functions and Operators.

Proposal

Define functions JSON.query and JSON.value specific to JSON stream properties in the new JSON vocabulary.

Imported from ODATA-1336