Optimize performance: Remove bulk date parsing, rely on on-demand conversion

Co-authored-by: zdrawku <11193764+zdrawku@users.noreply.github.com>

Author: Copilot

projects/igniteui-angular/src/lib/grids/pivot-grid/pivot-grid.component.ts

@@ -2401,7 +2401,6 @@ export class IgxPivotGridComponent extends IgxGridBaseDirective implements OnIni
         const columnDimensions: IPivotDimension[] = [];
         const rowDimensions: IPivotDimension[] = [];
         const values: IPivotValue[] = [];
-        const dateFields: string[] = [];
         let isFirstDate = true;
 
         fields.forEach((field) => {
@@ -2425,7 +2424,6 @@ export class IgxPivotGridComponent extends IgxGridBaseDirective implements OnIni
                     }
                 case "date":
                     {
-                        dateFields.push(field);
                         const dimension: IPivotDimension = new IgxPivotDateDimension(
                             {
                                 memberName: field,
@@ -2449,11 +2447,6 @@ export class IgxPivotGridComponent extends IgxGridBaseDirective implements OnIni
             }
         });
 
-        // Parse date-like values (timestamps and date strings) into Date objects
-        if (dateFields.length > 0) {
-            this.parseDateFields(data, dateFields);
-        }
-        
         const config: IPivotConfiguration = {
             columns: columnDimensions,
             rows: rowDimensions,
@@ -2462,39 +2455,6 @@ export class IgxPivotGridComponent extends IgxGridBaseDirective implements OnIni
         this.pivotConfiguration = config;
     }
 
-    /**
-     * @hidden
-     * Parses date-like values (timestamps and date strings) in the data into Date objects
-     */
-    private parseDateFields(data: any[], dateFields: string[]): void {
-        if (!data || data.length === 0) {
-            return;
-        }
-        
-        for (const record of data) {
-            for (const field of dateFields) {
-                const value = record[field];
-                // Skip if already a Date object or null/undefined
-                if (!value || value instanceof Date) {
-                    continue;
-                }
-                
-                // Convert timestamp or date string to Date object
-                if (typeof value === 'number' || typeof value === 'string') {
-                    try {
-                        const parsedDate = new Date(value);
-                        if (!isNaN(parsedDate.getTime())) {
-                            record[field] = parsedDate;
-                        }
-                    } catch (e) {
-                        // If parsing fails, leave the original value
-                        console.warn(`Failed to parse date value for field '${field}':`, value);
-                    }
-                }
-            }
-        }
-    }
-
     protected createColumnForDimension(value: any, data: any, parent: ColumnType, isGroup: boolean) {
         const key = value.value;
         const ref = isGroup ?

projects/igniteui-angular/src/lib/grids/pivot-grid/pivot-grid.spec.ts

@@ -2083,7 +2083,7 @@ describe('IgxPivotGrid #pivotGrid', () => {
                 expect(pivotGrid.values.map(x => x.enabled)).toEqual([true, true]);
             });
 
-            it('should auto-generate pivot config and parse date fields from timestamp values', () => {
+            it('should auto-generate pivot config and detect date fields from timestamp values', () => {
                 const pivotGrid = fixture.componentInstance.pivotGrid;
                 pivotGrid.pivotConfiguration = undefined;
                 pivotGrid.autoGenerateConfig = true;
@@ -2105,27 +2105,28 @@ describe('IgxPivotGrid #pivotGrid', () => {
                 expect(pivotGrid.pivotConfiguration.rows.map(x => x.memberName)).toEqual(['AllPeriods']);
                 expect(pivotGrid.pivotConfiguration.rows.map(x => x.enabled)).toEqual([true]);
 
-                // Verify the timestamp was converted to a Date object
-                expect(pivotGrid.data[0].Date instanceof Date).toBe(true);
-                expect(pivotGrid.data[0].Date.getTime()).toBe(TEST_TIMESTAMP);
+                // Verify the timestamp is still in its original format (not pre-parsed)
+                // IgxPivotDateDimension will handle parsing on-demand
+                expect(pivotGrid.data[0].Date).toBe(TEST_TIMESTAMP);
 
                 // values should be UnitPrice and UnitsSold (not Date)
                 expect(pivotGrid.values.length).toEqual(2);
                 expect(pivotGrid.values.map(x => x.member)).toEqual(['UnitPrice', 'UnitsSold']);
             });
 
-            it('should auto-generate pivot config and parse date fields from ISO date strings', () => {
+            it('should auto-generate pivot config and detect date fields from ISO date strings', () => {
                 const pivotGrid = fixture.componentInstance.pivotGrid;
                 pivotGrid.pivotConfiguration = undefined;
                 pivotGrid.autoGenerateConfig = true;
 
                 // Test with ISO date string
+                const TEST_DATE_STRING = '2008-06-20';
                 pivotGrid.data = [{
                     ProductCategory: 'Clothing', 
                     UnitPrice: 12.81, 
                     SellerName: 'Stanley',
                     Country: 'Bulgaria', 
-                    Date: '2008-06-20', 
+                    Date: TEST_DATE_STRING, 
                     UnitsSold: 282
                 }];
                 fixture.detectChanges();
@@ -2135,25 +2136,24 @@ describe('IgxPivotGrid #pivotGrid', () => {
                 expect(pivotGrid.pivotConfiguration.rows.map(x => x.memberName)).toEqual(['AllPeriods']);
                 expect(pivotGrid.pivotConfiguration.rows.map(x => x.enabled)).toEqual([true]);
 
-                // Verify the date string was converted to a Date object
-                expect(pivotGrid.data[0].Date instanceof Date).toBe(true);
-                expect(pivotGrid.data[0].Date.getFullYear()).toBe(2008);
-                expect(pivotGrid.data[0].Date.getMonth()).toBe(5); // June is month 5 (0-indexed)
-                expect(pivotGrid.data[0].Date.getDate()).toBe(20);
+                // Verify the date string is still in its original format (not pre-parsed)
+                // IgxPivotDateDimension will handle parsing on-demand
+                expect(pivotGrid.data[0].Date).toBe(TEST_DATE_STRING);
             });
 
-            it('should auto-generate pivot config and parse date fields from US format date strings', () => {
+            it('should auto-generate pivot config and detect date fields from US format date strings', () => {
                 const pivotGrid = fixture.componentInstance.pivotGrid;
                 pivotGrid.pivotConfiguration = undefined;
                 pivotGrid.autoGenerateConfig = true;
 
                 // Test with US format date string (MM/DD/YYYY)
+                const TEST_US_DATE_STRING = '10/24/2025';
                 pivotGrid.data = [{
                     ProductCategory: 'Clothing', 
                     UnitPrice: 12.81, 
                     SellerName: 'Stanley',
                     Country: 'Bulgaria', 
-                    Date: '10/24/2025', 
+                    Date: TEST_US_DATE_STRING, 
                     UnitsSold: 282
                 }];
                 fixture.detectChanges();
@@ -2163,11 +2163,9 @@ describe('IgxPivotGrid #pivotGrid', () => {
                 expect(pivotGrid.pivotConfiguration.rows.map(x => x.memberName)).toEqual(['AllPeriods']);
                 expect(pivotGrid.pivotConfiguration.rows.map(x => x.enabled)).toEqual([true]);
 
-                // Verify the date string was converted to a Date object
-                expect(pivotGrid.data[0].Date instanceof Date).toBe(true);
-                expect(pivotGrid.data[0].Date.getFullYear()).toBe(2025);
-                expect(pivotGrid.data[0].Date.getMonth()).toBe(9); // October is month 9 (0-indexed)
-                expect(pivotGrid.data[0].Date.getDate()).toBe(24);
+                // Verify the date string is still in its original format (not pre-parsed)
+                // IgxPivotDateDimension will handle parsing on-demand
+                expect(pivotGrid.data[0].Date).toBe(TEST_US_DATE_STRING);
             });
 
             it('should handle multiple date fields and enable only the first one', () => {
@@ -2196,9 +2194,10 @@ describe('IgxPivotGrid #pivotGrid', () => {
                 expect(rowDimensions[0].enabled).toBe(true);
                 expect(rowDimensions[1].enabled).toBe(false);
 
-                // Verify both date values were parsed
-                expect(pivotGrid.data[0].StartDate instanceof Date).toBe(true);
-                expect(pivotGrid.data[0].EndDate instanceof Date).toBe(true);
+                // Verify date values remain in their original format (not pre-parsed)
+                // IgxPivotDateDimension will handle parsing on-demand
+                expect(pivotGrid.data[0].StartDate).toBe(TEST_START_TIMESTAMP);
+                expect(pivotGrid.data[0].EndDate).toBe(TEST_END_DATE_STRING);
             });
 
             it('should not treat regular numbers as timestamps', () => {