Derived Metrics Bugs

[shangyian]

Summary

Shared Dimensions for Derived Metrics

When querying derived metrics, the system needed to correctly compute which dimensions are available. A derived metric that references multiple base metrics should be able to use dimensions from any of its base metrics (union), while multiple metrics queried together should only expose shared dimensions (intersection).

The changes modified get_shared_dimensions() to compute per-metric dimension unions first, then intersect across metrics. We also add get_metric_parents_map() to batch-fetch parent mappings while maintaining metric-to-parent relationships. This enables dimension determination for derived metrics to work correctly.

AST Column Compilation for Derived Metrics

Derived metric queries have no FROM clause - they reference base metrics directly as columns (e.g., SELECT default.revenue / default.orders). The AST compiler couldn't resolve these references with the right types.

The changes here extended Column.compile() to resolve metric references by looking up the metric node and getting its output type, and added support for dimension attribute references for ordering/filtering.

Pre-expanded Template Handling

Metric decomposition could produce pre-expanded aggregation templates like SUM(POWER(match_score, 2)) instead of the unexpanded SUM(POWER({}, 2)). The build_component_expression() function didn't handle these. This change adds detection for pre-expanded templates, which are parsed directly as complete SQL expressions.

Test Plan

• PR has an associated issue: #
• make check passes
• make test shows 100% unit test coverage

Deployment Plan

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