Optimize scrolling behavior of Discover table

Also:
* some minor cleanup

Signed-off-by: Miki <miki@amazon.com>

changelogs/fragments/6683.yml

@@ -0,0 +1,2 @@
+feat:
+- Optimize scrolling behavior of Discover table ([#6683](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/6683))

src/plugins/discover/public/application/components/data_grid/data_grid_table.tsx

@@ -3,8 +3,6 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import './_data_grid_table.scss';
-
 import React, { useState } from 'react';
 import { EuiPanel } from '@elastic/eui';
 import { IndexPattern, getServices } from '../../../opensearch_dashboards_services';

src/plugins/discover/public/application/components/default_discover_table/default_discover_table.tsx

@@ -38,6 +38,10 @@ export interface DefaultDiscoverTableProps {
   scrollToTop?: () => void;
 }
 
+// ToDo: These would need to be read from an upcoming config panel
+const PAGINATED_PAGE_SIZE = 50;
+const INFINITE_SCROLLED_PAGE_SIZE = 10;
+
 const DefaultDiscoverTableUI = ({
   columns,
   hits,
@@ -70,52 +74,75 @@ const DefaultDiscoverTableUI = ({
     isShortDots
   );
   const displayedColumnNames = displayedColumns.map((column) => column.name);
-  const pageSize = 10;
-  const [renderedRowCount, setRenderedRowCount] = useState(pageSize); // Start with 10 rows
-  const [displayedRows, setDisplayedRows] = useState(rows.slice(0, pageSize));
+
+  /* INFINITE_SCROLLED_PAGE_SIZE:
+   * Infinitely scrolling, a page of 10 rows is shown and then 4 pages are lazy-loaded for a total of 5 pages.
+   *   * The lazy-loading is mindful of the performance by monitoring the fps of the browser.
+   *   *`renderedRowCount` and `desiredRowCount` are only used in this method.
+   *
+   * PAGINATED_PAGE_SIZE
+   * Paginated, the view is broken into pages of 50 rows.
+   *   * `displayedRows` and `currentRowCounts` are only used in this method.
+   */
+  const [renderedRowCount, setRenderedRowCount] = useState(INFINITE_SCROLLED_PAGE_SIZE);
+  const [desiredRowCount, setDesiredRowCount] = useState(
+    Math.min(rows.length, 5 * INFINITE_SCROLLED_PAGE_SIZE)
+  );
+  const [displayedRows, setDisplayedRows] = useState(rows.slice(0, PAGINATED_PAGE_SIZE));
   const [currentRowCounts, setCurrentRowCounts] = useState({
     startRow: 0,
-    endRow: rows.length < pageSize ? rows.length : pageSize,
+    endRow: rows.length < PAGINATED_PAGE_SIZE ? rows.length : PAGINATED_PAGE_SIZE,
   });
+
   const observerRef = useRef<IntersectionObserver | null>(null);
-  const [sentinelEle, setSentinelEle] = useState<HTMLDivElement>();
-  // Need a callback ref since the element isn't set on the first render.
+  // `sentinelElement` is attached to the bottom of the table to observe when the table is scrolled all the way.
+  const [sentinelElement, setSentinelElement] = useState<HTMLDivElement>();
+  // `tableElement` is used for first auto-sizing and then fixing column widths
+  const [tableElement, setTableElement] = useState<HTMLTableElement>();
+  // Both need callback refs since the elements aren't set on the first render.
   const sentinelRef = useCallback((node: HTMLDivElement | null) => {
     if (node !== null) {
-      setSentinelEle(node);
+      setSentinelElement(node);
+    }
+  }, []);
+  const tableRef = useCallback((el: HTMLTableElement | null) => {
+    if (el !== null) {
+      setTableElement(el);
     }
   }, []);
 
   useEffect(() => {
-    if (sentinelEle) {
+    if (sentinelElement && !showPagination) {
       observerRef.current = new IntersectionObserver(
         (entries) => {
           if (entries[0].isIntersecting) {
-            setRenderedRowCount((prevRowCount) => prevRowCount + pageSize); // Load 50 more rows
+            // Load another batch of rows, some immediately and some lazily
+            setRenderedRowCount((prevRowCount) => prevRowCount + INFINITE_SCROLLED_PAGE_SIZE);
+            setDesiredRowCount((prevRowCount) => prevRowCount + 5 * INFINITE_SCROLLED_PAGE_SIZE);
           }
         },
         { threshold: 1.0 }
       );
 
-      observerRef.current.observe(sentinelEle);
+      observerRef.current.observe(sentinelElement);
     }
 
     return () => {
-      if (observerRef.current && sentinelEle) {
-        observerRef.current.unobserve(sentinelEle);
+      if (observerRef.current && sentinelElement) {
+        observerRef.current.unobserve(sentinelElement);
       }
     };
-  }, [sentinelEle]);
+  }, [sentinelElement, showPagination]);
 
+  // Page management when using a paginated table
   const [activePage, setActivePage] = useState(0);
-  const pageCount = Math.ceil(rows.length / pageSize);
-
+  const pageCount = Math.ceil(rows.length / PAGINATED_PAGE_SIZE);
   const goToPage = (pageNumber: number) => {
-    const startRow = pageNumber * pageSize;
+    const startRow = pageNumber * PAGINATED_PAGE_SIZE;
     const endRow =
-      rows.length < pageNumber * pageSize + pageSize
+      rows.length < pageNumber * PAGINATED_PAGE_SIZE + PAGINATED_PAGE_SIZE
         ? rows.length
-        : pageNumber * pageSize + pageSize;
+        : pageNumber * PAGINATED_PAGE_SIZE + PAGINATED_PAGE_SIZE;
     setCurrentRowCounts({
       startRow,
       endRow,
@@ -124,6 +151,60 @@ const DefaultDiscoverTableUI = ({
     setActivePage(pageNumber);
   };
 
+  // Lazy-loader of rows
+  const lazyLoadRequestFrameRef = useRef<number>(0);
+  const lazyLoadLastTimeRef = useRef<number>(0);
+
+  React.useEffect(() => {
+    if (!showPagination) {
+      const loadMoreRows = (time: number) => {
+        if (renderedRowCount < desiredRowCount) {
+          // Load more rows only if fps > 30, when calls are less than 33ms apart
+          if (time - lazyLoadLastTimeRef.current < 33) {
+            setRenderedRowCount((prevRowCount) => prevRowCount + INFINITE_SCROLLED_PAGE_SIZE);
+          }
+          lazyLoadLastTimeRef.current = time;
+          lazyLoadRequestFrameRef.current = requestAnimationFrame(loadMoreRows);
+        }
+      };
+      lazyLoadRequestFrameRef.current = requestAnimationFrame(loadMoreRows);
+    }
+
+    return () => cancelAnimationFrame(lazyLoadRequestFrameRef.current);
+  }, [showPagination, renderedRowCount, desiredRowCount]);
+
+  // Allow auto column-sizing using the initially rendered rows and then convert to fixed
+  const tableLayoutRequestFrameRef = useRef<number>(0);
+
+  useEffect(() => {
+    if (tableElement) {
+      // Load the first batch of rows and adjust the columns to the contents
+      tableElement.style.tableLayout = 'auto';
+
+      tableLayoutRequestFrameRef.current = requestAnimationFrame(() => {
+        if (tableElement) {
+          /* Get the widths for each header cell which is the column's width automatically adjusted to the content of
+           * the column. Apply the width as a style and change the layout to fixed. This is to
+           *   1) prevent columns from changing size when more rows are added, and
+           *   2) speed of rendering time of subsequently added rows.
+           *
+           * First cell is skipped because it has a dimention set already, and the last cell is skipped to allow it to
+           * grow as much as the table needs.
+           */
+          tableElement
+            .querySelectorAll('thead > tr > th:not(:first-child):not(:last-child)')
+            .forEach((th) => {
+              (th as HTMLTableCellElement).style.width = th.getBoundingClientRect().width + 'px';
+            });
+
+          tableElement.style.tableLayout = 'fixed';
+        }
+      });
+    }
+
+    return () => cancelAnimationFrame(tableLayoutRequestFrameRef.current);
+  }, [columns, tableElement]);
+
   return (
     indexPattern && (
       <>
@@ -138,7 +219,7 @@ const DefaultDiscoverTableUI = ({
             sampleSize={sampleSize}
           />
         ) : null}
-        <table data-test-subj="docTable" className="osd-table table">
+        <table data-test-subj="docTable" className="osd-table table" ref={tableRef}>
           <thead>
             <TableHeader
               displayedColumns={displayedColumns}
@@ -155,7 +236,7 @@ const DefaultDiscoverTableUI = ({
               (row: OpenSearchSearchHit, index: number) => {
                 return (
                   <TableRow
-                    key={index}
+                    key={row._id}
                     row={row}
                     columns={displayedColumnNames}
                     indexPattern={indexPattern}

src/plugins/discover/public/application/components/default_discover_table/table_header.tsx

@@ -39,7 +39,7 @@ export function TableHeader({
 }: Props) {
   return (
     <tr data-test-subj="docTableHeader" className="osdDocTableHeader">
-      <th style={{ width: '24px' }} />
+      <th style={{ width: '28px' }} />
       {displayedColumns.map((col) => {
         return (
           <TableHeaderColumn

src/plugins/discover/public/application/components/default_discover_table/table_row.tsx

@@ -30,7 +30,7 @@ export interface TableRowProps {
   isShortDots: boolean;
 }
 
-export const TableRow = ({
+const TableRowUI = ({
   row,
   columns,
   indexPattern,
@@ -185,3 +185,5 @@ export const TableRow = ({
     </>
   );
 };
+
+export const TableRow = React.memo(TableRowUI);