SuperDB

Pragmas

Pragmas control various language features and appear in a declaration block so their effect is lexically scoped. They have the form

pragma <id> [ = <expr> ]

where <id> is an identifier and <expr> is a constant expression that must evaluate at compile time without referencing any runtime state such as this or a field of this.

If <expr> is omitted, it defaults to true.

Pragmas must appear in the declaration section of a scope.

List of Pragmas

Currently, there are two supported pragmas.

• index_base - controls whether index expressions and slice expressions are 0-based or 1-based.
  • 0 for zero-based indexing
  • 1 for one-based indexing
• pg - controls the precedence of scoping for GROUP BY clauses in SQL operators
  • false to follow Google SQL semantics of resolving identifiers first from column aliases then from the input table
  • true to follow PostgreSQL semantics of resolving identifiers first from the input table then from the column aliases

Example

Controlling indexing and slicing

# spq
pragma index_base = 1
values {
  a: this[2:3],
  b: (
    pragma index_base = 0
    values this[0]
  )
}
# input
"bar"
[1,2,3]
# expected output
{a:"a",b:error("missing")}
{a:[2],b:1}