[DASHBOARDS] Add split multi-value fields setting for charts (#17907)

closes https://github.com/twentyhq/twenty/issues/17890



https://github.com/user-attachments/assets/dbf2ebe6-c2da-44d0-846e-d7fa9fac5f43

packages/twenty-server/src/engine/api/common/common-query-runners/types/group-by-field.types.ts

@@ -6,6 +6,7 @@ import { type FlatFieldMetadata } from 'src/engine/metadata-modules/flat-field-m
 export type GroupByRegularField = {
   fieldMetadata: FlatFieldMetadata;
   subFieldName?: string;
+  shouldUnnest?: boolean;
 };
 
 export type GroupByDateField = {

packages/twenty-server/src/engine/api/common/common-query-runners/utils/__tests__/get-group-by-expression.util.spec.ts

@@ -3,7 +3,10 @@ import {
   ObjectRecordGroupByDateGranularity,
 } from 'twenty-shared/types';
 
-import { type GroupByDateField } from 'src/engine/api/common/common-query-runners/types/group-by-field.types';
+import {
+  type GroupByDateField,
+  type GroupByRegularField,
+} from 'src/engine/api/common/common-query-runners/types/group-by-field.types';
 import { getGroupByExpression } from 'src/engine/api/common/common-query-runners/utils/get-group-by-expression.util';
 import { type FlatFieldMetadata } from 'src/engine/metadata-modules/flat-field-metadata/types/flat-field-metadata.type';
 
@@ -23,6 +26,16 @@ const buildGroupByDateField = (
   ...overrides,
 });
 
+const buildGroupByRegularField = (
+  overrides: Partial<GroupByRegularField> = {},
+): GroupByRegularField => ({
+  fieldMetadata: {
+    type: FieldMetadataType.MULTI_SELECT,
+    name: 'tags',
+  } as FlatFieldMetadata,
+  ...overrides,
+});
+
 describe('getGroupByExpression', () => {
   const columnNameWithQuotes = '"company"."createdAt"';
 
@@ -126,4 +139,36 @@ describe('getGroupByExpression', () => {
       expect(result).not.toContain('AT TIME ZONE');
     });
   });
+
+  describe('array unnest handling', () => {
+    const arrayColumnNameWithQuotes = '"company"."tags"';
+
+    it('should unnest array fields when split mode is enabled', () => {
+      const groupByField = buildGroupByRegularField({
+        shouldUnnest: true,
+      });
+
+      const result = getGroupByExpression({
+        groupByField,
+        columnNameWithQuotes: arrayColumnNameWithQuotes,
+      });
+
+      expect(result).toBe(
+        `UNNEST(CASE WHEN CARDINALITY(${arrayColumnNameWithQuotes}) > 0 THEN ${arrayColumnNameWithQuotes} ELSE ARRAY[${arrayColumnNameWithQuotes}[1]] END)`,
+      );
+    });
+
+    it('should keep plain column expression when split mode is disabled', () => {
+      const groupByField = buildGroupByRegularField({
+        shouldUnnest: false,
+      });
+
+      const result = getGroupByExpression({
+        groupByField,
+        columnNameWithQuotes: arrayColumnNameWithQuotes,
+      });
+
+      expect(result).toBe(arrayColumnNameWithQuotes);
+    });
+  });
 });

packages/twenty-server/src/engine/api/common/common-query-runners/utils/get-group-by-expression.util.ts

@@ -30,6 +30,10 @@ export const getGroupByExpression = ({
   if (
     !(isGroupByDateField(groupByField) || isGroupByRelationField(groupByField))
   ) {
+    if ('shouldUnnest' in groupByField && groupByField.shouldUnnest) {
+      return `UNNEST(CASE WHEN CARDINALITY(${columnNameWithQuotes}) > 0 THEN ${columnNameWithQuotes} ELSE ARRAY[${columnNameWithQuotes}[1]] END)`;
+    }
+
     return columnNameWithQuotes;
   }