The partition date picker

The partition date picker is the date tree in the Truncate Partitions dialog. It unfolds a table's partitions by year, month and day, and the dates you tick are the partitions the truncate acts on.

Where the picker appears

• On a Warehouse Fact table: open the table and go to Settings, then click Truncate. Pick your dates under Partition Dates in the Truncate Partitions dialog; the rest of that dialog is in Dimension and fact settings.
• Warehouse Dimension tables do not use the tree. A Dimension that stores history picks a Truncate Target instead.
• On a Lake staging table: open the table's popup and click Truncate. The tree fills the Truncate Partitions dialog; the flows around it are in Run, stop and troubleshoot loads and Staging tables.

How the tree is laid out

The tree opens on years, newest first. Open a year to see its months in calendar order, from January to December; open a month to see its dates, earliest to latest. Entries that fall on the same day sit together.

• Each date shows its day in the MMM dd, yyyy format, like Jan 05, 2026. When the date carries a time as well, a chip shows it in the HH:mm:ss format, like 14:00:00; a day-only date shows no chip.
• Year and month rows carry a badge with the number of dates below them; a year row reads like 12 dates.
• The picker reads the dates as the platform reports them: yyyy-MM-dd HH:mm:ss, an ISO timestamp with a T, or a plain yyyy-MM-dd day.
• Collapsing a year also collapses its months.

Pick the dates to truncate

Tick a date to add it to the truncate; untick it to leave the date out.

• A checkbox on a year or month row ticks all of its dates, or clears them when they are all ticked already. When only some of a group's dates are ticked, the group checkbox shows a dash.
• Select All ticks every date when nothing is ticked. When something is ticked, it clears the selection instead, so click it again to tick everything. The badge at the end of that row counts your progress, like 3 of 12 selected.

Read the row counts

• Each date row ends with the number of rows its partitions hold, like 1,234 rows.
• When the platform could not count a date, the row shows -. That means the count is unknown, not zero.
• A year or month row shows a total only when every date below it was counted. If one count is missing, the total is hidden rather than shown lower than it really is.

Questions, answered

What does the dash next to a date mean?

The platform could not count the rows in that date's partitions, so the number is unknown. It does not mean the date is empty.

What does "3 of 12 selected" count?

It counts dates: how many you have ticked out of all the dates in the tree. It does not count the rows behind them.

How do I pick a whole month at once?

Tick the checkbox on the month's row. It ticks every date in the month, or clears them when they are all ticked already. The same works on a year row for a whole year.

How do I select every date at once?

Click Select All while nothing is ticked. If dates are already ticked, it clears the selection first, so click it again to tick everything.

Why does a year or month row show no row total?

Because at least one of its dates has no known count. Rather than show a total that understates the removal, the row hides it.

In what order do the years and months appear?

Years come newest first, and months run in calendar order, January to December. Dates inside a month run earliest to latest.

Why do some dates show a time?

Some partition dates carry a time of day as well as a day. When they do, the row shows it in a chip, like 14:00:00, next to the date. A date without a time shows the day only.

Do my picks stay when I reopen the dialog?

No. Every time the Truncate Partitions dialog opens, the selection starts empty. On a Warehouse table, switching to another source system also clears your picks, because each source system has its own dates.