Add the negative --limit facility to dimension records and data IDs c…

…ommand line

This was missed before since we added negative support at the last minute.
We can't actually use that negative support handling because the
command line uses advanced query interface to do the dataset type
joining.

python/lsst/daf/butler/cli/opt/options.py

@@ -288,11 +288,16 @@ def _config_split(*args: Any) -> dict[str | None, str]:
 )
 
 
+_default_limit = -20_000
 limit_option = MWOptionDecorator(
     "--limit",
-    help=unwrap("Limit the number of records, by default all records are shown."),
+    help=unwrap(
+        f"""Limit the number of results that are processed. 0 means no limit. A negative
+        value specifies a cap where a warning will be issued if the cap is hit.
+        Default value is {_default_limit}."""
+    ),
     type=int,
-    default=0,
+    default=_default_limit,
 )
 
 offset_option = MWOptionDecorator(

python/lsst/daf/butler/script/queryDataIds.py

@@ -57,6 +57,14 @@ def __init__(self, dataIds: Iterable[DataCoordinate]):
         # use dict to store dataIds as keys to preserve ordering
         self.dataIds = dict.fromkeys(dataIds)
 
+    def __len__(self) -> int:
+        return len(self.dataIds)
+
+    def pop_last(self) -> None:
+        if self.dataIds:
+            final_key = list(self.dataIds.keys())[-1]
+            self.dataIds.pop(final_key)
+
     def getAstropyTable(self, order: bool) -> AstropyTable:
         """Get the table as an astropy table.
 
@@ -195,12 +203,21 @@ def queryDataIds(
             results = results.where(where)
         if order_by:
             results = results.order_by(*order_by)
-        if limit > 0:
-            results = results.limit(limit)
+        query_limit = abs(limit)
+        warn_limit = False
+        if limit != 0:
+            if limit < 0:
+                query_limit += 1
+                warn_limit = True
+
+            results = results.limit(query_limit)
 
         if results.any(exact=False):
             if results.dimensions:
                 table = _Table(results)
+                if warn_limit and len(table) == query_limit:
+                    table.pop_last()
+                    _LOG.warning("More data IDs are available than the request limit of %d", abs(limit))
                 if not table.dataIds:
                     return None, "Post-query region filtering removed all rows, since nothing overlapped."
                 return table.getAstropyTable(not order_by), None

python/lsst/daf/butler/script/queryDimensionRecords.py

@@ -27,6 +27,7 @@
 
 from __future__ import annotations
 
+import logging
 from operator import attrgetter
 from typing import Any
 
@@ -36,6 +37,8 @@
 from .._butler import Butler
 from .._timespan import Timespan
 
+_LOG = logging.getLogger(__name__)
+
 
 def queryDimensionRecords(
     repo: str,
@@ -100,10 +103,19 @@ def queryDimensionRecords(
             query_results = query_results.where(where)
         if order_by:
             query_results = query_results.order_by(*order_by)
-        if limit > 0:
-            query_results = query_results.limit(limit)
+        query_limit = abs(limit)
+        warn_limit = False
+        if limit != 0:
+            if limit < 0:
+                query_limit += 1
+                warn_limit = True
+
+            query_results = query_results.limit(query_limit)
 
         records = list(query_results)
+        if warn_limit and len(records) == query_limit:
+            records.pop(-1)
+            _LOG.warning("More data IDs are available than the request limit of %d", abs(limit))
 
         if not records:
             return None