This module defines functions that translate from the Postgres IR into Postgres SQL AST.

NOTE: These functions processAnnAggregateSelect, processAnnSimpleSelect, processConnectionSelect, are all mutually recursive.

These functions are generally called from the top level functions in Translate.Select, and the call stack looks like:

• selectQuerySQL -> mkSQLSelect -> processAnnSimpleSelect -> processSelectParams/processAnnFields
• selectAggregateQuerySQL -> mkAggregateSelect -> processAnnAggregateSelect -> processSelectParams/processAnnFields
• connetionSelectQuerySQL -> mkConnectionSelect -> processConnectionSelection -> processSelectParams

SelectSource consists of a prefix, a source, a boolean conditional expression, and info on whether sorting or slicing is done (needed to handle the LIMIT optimisation)