Query Abstract Syntax Tree
The query abstract syntax tree (query AST) is constructed from a minimal set of operators and a syntax similar to s-expressions but in JSON arrays for portability on the web platform. A valid expression is either a value (number, string, boolean or object) or an operation denoted as an array whose first element is an operator and the rest are operands. The following operators are currently supported:
| Operator | Operands | Result | Description |
|---|---|---|---|
$ |
(none) | value | Get current row |
. |
2+ string | value | Get field from the first operand |
~ |
2 strings | null/object | Regular expression matcher |
+ |
1+ values | value | Sum or strings/arrays concatenation |
- |
1+ numbers | number | Subtraction |
* |
1+ numbers | number | Multiplication |
/ |
1+ numbers | number | Division |
% |
2 numbers | number | Modulo |
&& |
2 arrays | boolean | Logical intersection |
& |
0+ booleans | value | Logical and |
| |
0+ booleans | value | Logical or |
== |
2+ values | boolean | Equality |
!= |
2+ values | boolean | Inequality |
> |
2+ values | boolean | Greater than comparison |
>= |
2+ values | boolean | Greater or equal comparison |
< |
2+ values | boolean | Less than comparison |
<= |
2+ values | boolean | Less or equal comparison |
! |
1 boolean | boolean | Logical not |
Behaviors involving JSON null is deliberately left undefined. The reference implementation considers queries with operations containing null’s as malformed, but does not complain about the appearance of null elsewhere; however core API users must not rely on such implementation details.