Promscale Tag Map Demo

Expose spans as a view over tag_map_denormalize function and use a support function on the = operator to optimize tag search.

Considerations:

1. This approach in conjunction with the fact we provide -> in our own schema results in an unpleasant scenario: if the user ends up issuing -> operator while ps_trace schema isn't path of their search_path, then _ps_trace.tag_map will be implicitly cast into jsonb and the built-in -> will be used, which will result in extremely poor performance.

2. We have several options regarding how we want our custom nodes to look in the plan output:

typedef enum CoercionForm
{
    COERCE_EXPLICIT_CALL,       /* display as a function call */
    COERCE_EXPLICIT_CAST,       /* display as an explicit cast */
    COERCE_IMPLICIT_CAST,       /* implicit cast, so hide it */
    COERCE_SQL_SYNTAX           /* display with SQL-mandated special syntax */
} CoercionForm;

For now I've decided to stick with COERCE_EXPLICIT_CALL

notes:

Source

select
        ...
    from ps_trace.spans
    where
        span_tags -> 'Key_1' = '"val_27"';

Translation:

select
        ...
    from _ps_trace.maps
    where
        denormalize(map) -> 'Key_1' = '"val_27"';

Target

select
        ...
    from _ps_trace.maps
    where map <@ (select find_label_ids('Key_1', '"val_27"'))

Current

select
        ...
    from _ps_trace.maps
    where map <@ find_label_ids('Key_1', '"val_27"')