Automatic Hidden Tables
What It Detects
Section titled “What It Detects”This flag identifies hidden tables that are automatically generated by Power BI features, most commonly:
- Auto date/time tables — Power BI creates a hidden date hierarchy table for every date/datetime column in the model when the “Auto date/time” option is enabled.
- Auto-generated aggregation tables — Created by the automatic aggregation feature.
- Performance Analyzer tables — Temporary tables created during profiling sessions that may persist.
Why It Matters
Section titled “Why It Matters”- Model bloat — Each auto date/time table adds a hidden calendar table per date column. A model with 15 date columns generates 15 hidden date tables, each containing years of date rows.
- Memory consumption — Auto date/time tables can account for 10–30% of the model’s total memory footprint in models with many date columns.
- Slower refresh — The hidden tables are recalculated during every refresh cycle.
- DAX conflicts — Auto date/time hierarchies can produce unexpected results in time-intelligence calculations, especially when the model already has an explicit Date table.
- Non-obvious impact — Because the tables are hidden, developers may not realize they exist or understand their memory cost.
Trigger Conditions
Section titled “Trigger Conditions”A table is flagged when any of the following are true:
- The table name matches the auto date/time pattern:
LocalDateTable_*orDateTableTemplate_*. - The table is marked as hidden and is not referenced by any user-created relationship, measure, or visual.
- The table was generated by a Power BI automatic feature (detected via model metadata annotations).
Threshold: Any auto-generated hidden table is flagged.
Output
Section titled “Output”| Field | Description |
|---|---|
tableName | Name of the hidden table (e.g., LocalDateTable_xxxxxxxx) |
generatedBy | Feature that created the table (e.g., “Auto date/time”) |
associatedColumn | The date column that triggered the table creation |
estimatedSizeBytes | Estimated memory consumed by the hidden table |
datasetName | Semantic model name |
workspaceName | Workspace name |
Notes and Edge Cases
Section titled “Notes and Edge Cases”- Disabling auto date/time — To prevent these tables from being created, go to Power BI Desktop > File > Options > Current File > Data Load > uncheck “Auto date/time”. This must be done per .pbix file or set as a global default under Global > Data Load.
- Existing explicit date table — If your model already has a dedicated Date/Calendar dimension table marked as a date table, the auto date/time tables are redundant and should be disabled.
- Cannot delete individually — You cannot delete individual auto date/time tables. You must disable the feature globally for the model, which removes all of them at once. After disabling, ensure any date hierarchies used in report visuals are updated to use the explicit date table.
Related Flags
Section titled “Related Flags”- Unused Tables — Auto-generated tables are a specific subset of potentially unused tables, but handled by this dedicated flag.
- Unused Columns — The columns within auto-generated tables are also unused by definition.