Upload & preview

Load files into existing tables and inspect rows without writing SQL.

File upload

Upload CSV, TSV or JSON files into an existing table (requires table:insert):

1. Open the table in the Explorer and choose Upload data.
2. Select the file — .csv, .tsv or .json.
3. Map/confirm the target columns (header handling follows the format: headers on first row for CSV/TSV, object keys for JSON).
4. Start the upload — rows are inserted via the server proxy in batches.

Behavior notes:

• Uploads append to the table; they don't truncate
• Format errors surface per batch with row context — fix the file and retry rather than fighting partial state
• Very large files: prefer ClickHouse-native bulk loading (clickhouse-client) and keep the UI upload for team-sized datasets
• All inserts pass data access rules — the target table must be allowed

Data preview

Every table opens with a paginated sample:

• Bounded reads (server caps rows per page — configurable via preferences' max-rows default)
• Sortable columns and quick filters on the sampled page
• Column types shown alongside values — catches Nullable/stringly-typed issues early

The preview is a SELECT … LIMIT through the security pipeline; table:select gates it.

From preview to action