feat: pickTableColumns utility function and update documentation

docs/table-introspect-api.md

@@ -30,3 +30,17 @@ const table = pgTable('table', {
 
 const columns/*: { id: ..., name: ... } */ = getTableColumns(table);
 ```
+
+```ts
+import { pgTable, pickTableColumns } from 'drizzle-orm/pg-core';
+
+const table = pgTable('table', {
+  id: integer('id').primaryKey(),
+  name: text('name'),
+});
+
+const colums = pickTableColumns(table, {
+  id: true,
+  name: false,
+});
+```

drizzle-orm/src/utils.ts

@@ -188,6 +188,16 @@ export function getTableColumns<T extends Table>(table: T): T['_']['columns'] {
 	return table[Table.Symbol.Columns];
 }
 
+export function pickTableColumns<T extends Table>(
+  table: T,
+  includedColumns: Partial<Record<keyof T['_']['columns'], true>>
+): Pick<T['_']['columns'], keyof typeof includedColumns> {
+  const allColumns = table[Table.Symbol.Columns];
+  return Object.fromEntries(
+    Object.entries(allColumns).filter(([key]) => key in includedColumns)
+  ) as any;
+}
+
 export function getViewSelectedFields<T extends View>(view: T): T['_']['selectedFields'] {
 	return view[ViewBaseConfig].selectedFields;
 }

integration-tests/tests/utils/table-columns.test.ts

@@ -0,0 +1,37 @@
+import { describe, expect, test } from 'vitest';
+import { integer, sqliteTable, text } from 'drizzle-orm/sqlite-core';
+import { getTableColumns, pickTableColumns } from 'drizzle-orm';
+
+describe('table columns utils', () => {
+  const users = sqliteTable('users', {
+    id: integer('id').primaryKey(),
+    name: text('name'),
+    email: text('email'),
+  });
+
+  test('getTableColumns should return all columns', () => {
+    const columns = getTableColumns(users);
+
+    expect(Object.keys(columns)).toEqual(['id', 'name', 'email']);
+    expect(columns.id.name).toBe('id');
+    expect(columns.name.name).toBe('name'); 
+    expect(columns.email.name).toBe('email');
+  });
+
+  test('pickTableColumns should return only selected columns', () => {
+    const columns = pickTableColumns(users, {
+      id: true,
+      name: true
+    });
+
+    expect(Object.keys(columns)).toEqual(['id', 'name']);
+    expect(columns.id.name).toBe('id');
+    expect(columns.name.name).toBe('name');
+    expect(columns.email).toBeUndefined();
+  });
+
+  test('pickTableColumns should return empty object if no columns selected', () => {
+    const columns = pickTableColumns(users, {});
+    expect(Object.keys(columns)).toEqual([]);
+  });
+});