perspective cache - basic design

packages/datalib/src/PerspectiveCache.ts

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+import { RangeDefinition } from 'dbgate-types';
+import { PerspectiveDataLoadProps } from './PerspectiveDataProvider';
+import _pick from 'lodash/pick';
+import _omit from 'lodash/omit';
+import _difference from 'lodash/difference';
+import debug from 'debug';
+
+const dbg = debug('dbgate:PerspectiveCache');
+
+export class PerspectiveCacheTable {
+  constructor(props: PerspectiveDataLoadProps) {
+    this.schemaName = props.schemaName;
+    this.pureName = props.pureName;
+    this.bindingColumns = props.bindingColumns;
+    this.dataColumns = props.dataColumns;
+    this.loadedAll = false;
+  }
+
+  schemaName: string;
+  pureName: string;
+  bindingColumns?: string[];
+  dataColumns: string[];
+  loadedAll: boolean;
+  loadedRows: any[] = [];
+  get loadedCount() {
+    return this.loadedRows.length;
+  }
+
+  getRowsResult(props: PerspectiveDataLoadProps): { rows: any[]; incomplete: boolean } {
+    return {
+      rows: this.loadedRows.slice(0, props.topCount),
+      incomplete: props.topCount < this.loadedCount || !this.loadedAll,
+    };
+  }
+}
+
+export class PerspectiveCache {
+  constructor(public stableStringify) {}
+
+  tables: { [tableKey: string]: PerspectiveCacheTable } = {};
+
+  getTableCache(props: PerspectiveDataLoadProps) {
+    const tableKey = this.stableStringify(_omit(props, ['range', 'bindingValues', 'dataColumns']));
+    let res = this.tables[tableKey];
+
+    if (res && _difference(props.dataColumns, res.dataColumns).length > 0) {
+      dbg('Delete cache because incomplete columns', props.pureName, res.dataColumns);
+
+      // we have incomplete cache
+      delete this.tables[tableKey];
+      res = null;
+    }
+
+    if (!res) {
+      res = new PerspectiveCacheTable(props);
+      this.tables[tableKey] = res;
+      return res;
+    }
+
+    // cache could be used
+    return res;
+  }
+}