Comments and cleanup

src/plugins/discover/public/application/main/hooks/use_esql_mode.ts

@@ -74,7 +74,12 @@ export function useEsqlMode({
             return;
           }
 
+          // We need to reset the default profile state on index pattern changes
+          // when loading starts to ensure the correct pre fetch state is available
+          // before data fetching is triggered
           if (next.fetchStatus === FetchStatus.LOADING) {
+            // We have to grab the current query from appState
+            // here since nextQuery has not been updated yet
             const appStateQuery = stateContainer.appState.getState().query;
 
             if (isOfAggregateQueryType(appStateQuery)) {
@@ -86,6 +91,7 @@ export function useEsqlMode({
                 getIndexPatternFromESQLQuery(appStateQuery.esql) !==
                 getIndexPatternFromESQLQuery(prev.current.query);
 
+              // Reset all default profile state when index pattern changes
               if (indexPatternChanged) {
                 stateContainer.internalState.transitions.setResetDefaultProfileState({
                   columns: true,
@@ -94,6 +100,8 @@ export function useEsqlMode({
                 });
               }
             }
+
+            return;
           }
 
           if (next.fetchStatus !== FetchStatus.PARTIAL) {
@@ -132,6 +140,8 @@ export function useEsqlMode({
           const { viewMode } = stateContainer.appState.getState();
           const changeViewMode = viewMode !== getValidViewMode({ viewMode, isEsqlMode: true });
 
+          // If the index pattern hasn't changed, but the available columns have changed
+          // due to transformational commands, reset the associated default profile state
           if (!indexPatternChanged && allColumnsChanged) {
             stateContainer.internalState.transitions.setResetDefaultProfileState({
               columns: true,

src/plugins/discover/public/application/main/state_management/discover_data_state_container.ts

@@ -277,6 +277,8 @@ export function getDataStateContainer({
             disableNextFetchOnStateChange$.next(false);
           }
 
+          // Trigger chart fetching after the pre fetch state has been updated
+          // to ensure state values that would affect data fetching are set
           fetchChart$.next();
 
           abortController = new AbortController();
@@ -302,6 +304,8 @@ export function getDataStateContainer({
                 await appStateContainer.replaceUrlState(postFetchStateUpdate);
               }
 
+              // Clear the default profile state flags after the data fetching
+              // is done so refetches don't reset the state again
               internalStateContainer.transitions.setResetDefaultProfileState({
                 columns: false,
                 rowHeight: false,

src/plugins/discover/public/application/main/state_management/utils/build_state_subscribe.ts

@@ -160,7 +160,7 @@ export const buildStateSubscribe =
 
       if (dataState.disableNextFetchOnStateChange$.getValue()) {
         addLog(
-          '[buildStateSubscribe] fetch disabled on state changes',
+          '[buildStateSubscribe] next fetch skipped on state change',
           JSON.stringify(logData, null, 2)
         );
 

src/plugins/discover/public/application/main/state_management/utils/get_default_profile_state.ts

@@ -31,6 +31,11 @@ export const getDefaultProfileState = ({
   const defaultState = getDefaultState(profilesManager, dataView);
 
   return {
+    /**
+     * Returns state that should be updated before data fetching occurs,
+     * for example state used as part of the data fetching process
+     * @returns The state to reset to before fetching data
+     */
     getPreFetchState: () => {
       const stateUpdate: DiscoverAppState = {};
 
@@ -44,6 +49,12 @@ export const getDefaultProfileState = ({
 
       return Object.keys(stateUpdate).length ? stateUpdate : undefined;
     },
+
+    /**
+     * Returns state that should be updated after data fetching occurs,
+     * for example state used to modify the UI after receiving data
+     * @returns The state to reset to after fetching data
+     */
     getPostFetchState: ({
       defaultColumns,
       esqlQueryColumns,

src/plugins/unified_histogram/public/container/container.tsx

@@ -95,7 +95,7 @@ export type UnifiedHistogramApi = {
 export const UnifiedHistogramContainer = forwardRef<
   UnifiedHistogramApi,
   UnifiedHistogramContainerProps
->(({ onBreakdownFieldChange, onVisContextChanged, ...containerProps }, ref) => {
+>(({ breakdownField, onBreakdownFieldChange, onVisContextChanged, ...containerProps }, ref) => {
   const [layoutProps, setLayoutProps] = useState<LayoutProps>();
   const [localStorageKeyPrefix, setLocalStorageKeyPrefix] = useState<string>();
   const [stateService, setStateService] = useState<UnifiedHistogramStateService>();
@@ -158,8 +158,7 @@ export const UnifiedHistogramContainer = forwardRef<
     searchSessionId,
     requestAdapter,
     columns,
-    breakdownField: initialBreakdownField,
-    ...pick(containerProps, 'breakdownField'),
+    breakdownField: breakdownField ?? initialBreakdownField,
     onBreakdownFieldChange,
   });