GitHub Issue #1607: Return selectRows total count without the rows query

api/src/org/labkey/api/action/ApiQueryResponse.java

@@ -75,6 +75,7 @@ public class ApiQueryResponse implements ApiResponse
     private RenderContext _ctx = null;
     private boolean _schemaEditable = false;
     private boolean _metaDataOnly;
+    private boolean _countOnly = false;
     private DataRegion _dataRegion;
     private TableInfo _tinfo = null;
     private List<DisplayColumn> _displayColumns = null;
@@ -147,6 +148,16 @@ public void render(ApiResponseWriter writer) throws Exception
                 if (_metaDataOnlyIncludesEmptyRowset)
                     writeEmptyRowset(writer);
             }
+            else if (_countOnly)
+            {
+                loadTotalRowsOnly();
+                if (_dataRegion.getTotalRows() != null)
+                    _rowCount = _dataRegion.getTotalRows();
+
+                if (_includeMetaData)
+                    writeMetaData(writer);
+                writeEmptyRowset(writer);
+            }
             else
             {
                 // First run the query, so on potential SQLException we only serialize the exception instead of outputting all the metadata before the exception
@@ -170,8 +181,11 @@ public void render(ApiResponseWriter writer) throws Exception
                         _rowCount = _dataRegion.getTotalRows();
                     }
                 }
+            }
 
-                long rowCount = _rowCount > 0 ? _rowCount : _offset + _numRespRows;
+            if (!_metaDataOnly)
+            {
+                long rowCount = _rowCount > 0 || _countOnly ? _rowCount : _offset + _numRespRows;
                 writer.writeProperty("rowCount", rowCount);
 
                 if (_includeMetaData)
@@ -268,9 +282,7 @@ protected void writeMetaData(ApiResponseWriter writer) throws Exception
 
     protected Results getResults() throws Exception
     {
-        // If we're going to be writing JSON back, which is tolerant of extra spaces, allow async so we
-        // can monitor if the client has stopped listening. XML doesn't take kindly to leading spaces
-        _dataRegion.setAllowAsync(ApiResponseWriter.getResponseFormat(_viewContext.getRequest(), ApiResponseWriter.Format.JSON).isJson());
+        _dataRegion.setAllowAsync(isAllowAsync());
         try
         {
             return _dataRegion.getResults(_ctx);
@@ -281,6 +293,26 @@ protected Results getResults() throws Exception
         }
     }
 
+    protected void loadTotalRowsOnly()
+    {
+        _dataRegion.setAllowAsync(isAllowAsync());
+        try
+        {
+            _dataRegion.loadTotalRowsOnly(_ctx);
+        }
+        catch (ConversionException e)
+        {
+            throw new ApiUsageException(e);
+        }
+    }
+
+    // If we're going to be writing JSON back, which is tolerant of extra spaces, allow async so we
+    // can monitor if the client has stopped listening. XML doesn't take kindly to leading spaces
+    private boolean isAllowAsync()
+    {
+        return ApiResponseWriter.getResponseFormat(_viewContext.getRequest(), ApiResponseWriter.Format.JSON).isJson();
+    }
+
     public List<FieldKey> getFieldKeys()
     {
         return _fieldKeys;
@@ -328,6 +360,12 @@ public void includeStyle(boolean withStyle)
         _doItWithStyle = withStyle;
     }
 
+    /** Return only rowCount (and metadata, if requested) via a COUNT(*) query, skipping the rows query. */
+    public void countOnly(boolean countOnly)
+    {
+        _countOnly = countOnly;
+    }
+
     protected double getFormatVersion()
     {
         return 8.3;

api/src/org/labkey/api/assay/AssayProtocolSchema.java

@@ -41,8 +41,8 @@
 import org.labkey.api.data.RenderContext;
 import org.labkey.api.data.Results;
 import org.labkey.api.data.SQLFragment;
+import org.labkey.api.data.ShowRows;
 import org.labkey.api.data.Sort;
-import org.labkey.api.data.Table;
 import org.labkey.api.data.TableInfo;
 import org.labkey.api.exp.PropertyDescriptor;
 import org.labkey.api.exp.api.ExpProtocol;
@@ -711,7 +711,7 @@ public void addQCWarningIndicator(QueryView baseQueryView, ViewContext context,
                             QuerySettings qs = getSettings(viewContext, settings.getDataRegionName(), settings.getQueryName());
 
                             // we want all the rows
-                            qs.setMaxRows(Table.ALL_ROWS);
+                            qs.setShowRows(ShowRows.ALL);
                             QueryView allResultsQueryView = createAllResultsQueryView(viewContext, qs);
 
                             DataView dataView = allResultsQueryView.createDataView();

api/src/org/labkey/api/data/DataRegion.java

@@ -851,16 +851,7 @@ public Map<String, List<Aggregate.Result>> getAggregateResults(RenderContext ctx
 
                     newAggregates.add(Aggregate.createCountStar());
                     _aggregateResults = ctx.getAggregates(_displayColumns, getTable(), getSettings(), getName(), newAggregates, getQueryParameters(), isAllowAsync());
-                    List<Aggregate.Result> result = _aggregateResults.remove(Aggregate.STAR);
-
-                    //Issue 14863: add null check
-                    if (result != null && !result.isEmpty())
-                    {
-                        Aggregate.Result countStarResult = result.getFirst();
-                        _totalRows = 0L;
-                        if (countStarResult.getValue() instanceof Number)
-                            _totalRows = ((Number) countStarResult.getValue()).longValue();
-                    }
+                    setTotalRowsFromCountStar(_aggregateResults.remove(Aggregate.STAR));
                 }
             }
             else
@@ -876,6 +867,42 @@ public Map<String, List<Aggregate.Result>> getAggregateResults(RenderContext ctx
         return _aggregateResults;
     }
 
+    /** Sets the total row count from a COUNT(*) aggregate alone, without selecting any rows. */
+    public void loadTotalRowsOnly(RenderContext ctx)
+    {
+        if (!hasPermission(ctx, ReadPermission.class))
+            throw new UnauthorizedException();
+
+        TableInfo table = getTable();
+        if (null == table)
+            throw new NotFoundException("Table or query not found: " + getSettings().getQueryName());
+
+        DataRegion oldRegion = ctx.getCurrentRegion();
+        ctx.setCurrentRegion(this);
+        try
+        {
+            Map<String, List<Aggregate.Result>> aggregates = ctx.getAggregates(_displayColumns, table, getSettings(), getName(), List.of(Aggregate.createCountStar()), getQueryParameters(), isAllowAsync());
+            setTotalRowsFromCountStar(aggregates.get(Aggregate.STAR));
+            _aggregateResults = Collections.emptyMap();
+        }
+        finally
+        {
+            ctx.setCurrentRegion(oldRegion);
+        }
+    }
+
+    private void setTotalRowsFromCountStar(@Nullable List<Aggregate.Result> result)
+    {
+        //Issue 14863: add null check
+        if (result == null || result.isEmpty())
+            return;
+
+        Aggregate.Result countStarResult = result.getFirst();
+        _totalRows = 0L;
+        if (countStarResult.getValue() instanceof Number n)
+            _totalRows = n.longValue();
+    }
+
     @NotNull
     private List<Aggregate> getSummaryStatsAggregates(List<AnalyticsProviderItem> providers)
     {

api/src/org/labkey/api/data/RenderContext.java

@@ -350,7 +350,10 @@ public Map<String, List<Aggregate.Result>> getAggregates(List<DisplayColumn> dis
         if (null != QueryService.get())
             cols = QueryService.get().ensureRequiredColumns(tinfo, cols, filter, sort, ignoredAggregateFilters);
 
-        if (!ignoredAggregateFilters.equals(_ignoredColumnFilters))
+        // Count-only requests skip the main query, so there's nothing to match; adopt the aggregate's set for filter messages
+        if (_results == null)
+            _ignoredColumnFilters.addAll(ignoredAggregateFilters);
+        else if (!ignoredAggregateFilters.equals(_ignoredColumnFilters))
         {
             // This should never happen, but if it did, the totals wouldn't match, so we won't calculate them.
             _log.error("Aggregate filter columns do not match main.  Aggregate:{} Main:{}", ignoredAggregateFilters, _ignoredColumnFilters);

api/webapp/clientapi/dom/DataRegion.js

@@ -3829,7 +3829,7 @@ if (!LABKEY.DataRegions) {
             containerPath: region.containerPath,
             filterArray: LABKEY.Filter.getFiltersFromParameters({ ...params, ...jsonData.filters }, params.dataRegionName),
             sort: undefined,
-            maxRows: 1,
+            maxRows: 0, // GH Issue 1607: with includeTotalCount, returns only the row count
             offset: 0,
             includeMetadata: false,
             includeDetailsColumn: false,

query/src/org/labkey/query/controllers/QueryController.java

@@ -3457,6 +3457,13 @@ public void setIncludeTotalCount(boolean includeTotalCount)
             _includeTotalCount = includeTotalCount;
         }
 
+        /** True when the request sent includeTotalCount rather than leaving it at its default. */
+        public boolean isIncludeTotalCountSet()
+        {
+            return null != getViewContext().getRequest().getParameter("includeTotalCount") ||
+                    (null != _initParameters && null != _initParameters.getPropertyValue("includeTotalCount"));
+        }
+
         public boolean isIncludeStyle()
         {
             return _includeStyle;
@@ -3577,7 +3584,10 @@ public ApiResponse execute(APIQueryForm form, BindException errors)
             }
 
             boolean isEditable = isQueryEditable(view.getTable());
-            boolean metaDataOnly = form.getQuerySettings().getMaxRows() == 0;
+            boolean noRows = form.getQuerySettings().getMaxRows() == 0;
+            // GH Issue 1607: maxRows=0 with an explicit includeTotalCount=true returns just the row count
+            boolean countOnly = noRows && form.isIncludeTotalCount() && form.isIncludeTotalCountSet();
+            boolean metaDataOnly = noRows && !countOnly;
             boolean arrayMultiValueColumns = getRequestedApiVersion() >= 16.2;
             boolean includeFormattedValue = getRequestedApiVersion() >= 17.1;
 
@@ -3607,6 +3617,7 @@ else if (getRequestedApiVersion() >= 9.1)
                         form.isIncludeDisplayValues(), form.isIncludeMetadata());
             }
             response.includeStyle(form.isIncludeStyle());
+            response.countOnly(countOnly);
 
             // Issues 29515 and 32269 - force key and other non-requested columns to be sent back, but only if the client has
             // requested minimal columns, as we now do for ExtJS stores