mirror of https://github.com/AMT-Cheif/drift.git
98 lines
3.0 KiB
Dart
98 lines
3.0 KiB
Dart
import 'package:drift/drift.dart';
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import 'tables/filename.dart';
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// #docregion joinIntro
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// We define a data class to contain both a todo entry and the associated
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// category.
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class EntryWithCategory {
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EntryWithCategory(this.entry, this.category);
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final Todo entry;
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final Category? category;
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}
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// #enddocregion joinIntro
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extension GroupByQueries on MyDatabase {
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// #docregion joinIntro
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// in the database class, we can then load the category for each entry
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Stream<List<EntryWithCategory>> entriesWithCategory() {
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final query = select(todos).join([
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leftOuterJoin(categories, categories.id.equalsExp(todos.category)),
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]);
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// see next section on how to parse the result
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// #enddocregion joinIntro
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// #docregion results
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return query.watch().map((rows) {
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return rows.map((row) {
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return EntryWithCategory(
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row.readTable(todos),
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row.readTableOrNull(categories),
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);
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}).toList();
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});
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// #enddocregion results
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// #docregion joinIntro
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}
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// #enddocregion joinIntro
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// #docregion countTodosInCategories
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Future<void> countTodosInCategories() async {
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final amountOfTodos = todos.id.count();
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final query = select(categories).join([
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innerJoin(
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todos,
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todos.category.equalsExp(categories.id),
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useColumns: false,
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)
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]);
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query
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..addColumns([amountOfTodos])
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..groupBy([categories.id]);
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final result = await query.get();
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for (final row in result) {
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print('there are ${row.read(amountOfTodos)} entries in'
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'${row.readTable(categories)}');
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}
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}
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// #enddocregion countTodosInCategories
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// #docregion averageItemLength
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Stream<double> averageItemLength() {
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final avgLength = todos.content.length.avg();
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final query = selectOnly(todos)..addColumns([avgLength]);
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return query.map((row) => row.read(avgLength)!).watchSingle();
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}
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// #enddocregion averageItemLength
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// #docregion otherTodosInSameCategory
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/// Searches for todo entries in the same category as the ones having
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/// `titleQuery` in their titles.
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Future<List<Todo>> otherTodosInSameCategory(String titleQuery) async {
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// Since we're adding the same table twice (once to filter for the title,
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// and once to find other todos in same category), we need a way to
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// distinguish the two tables. So, we're giving one of them a special name:
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final otherTodos = alias(todos, 'inCategory');
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final query = select(otherTodos).join([
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// In joins, `useColumns: false` tells drift to not add columns of the
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// joined table to the result set. This is useful here, since we only join
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// the tables so that we can refer to them in the where clause.
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innerJoin(categories, categories.id.equalsExp(otherTodos.category),
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useColumns: false),
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innerJoin(todos, todos.category.equalsExp(categories.id),
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useColumns: false),
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])
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..where(todos.title.contains(titleQuery));
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return query.map((row) => row.readTable(otherTodos)).get();
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}
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// #enddocregion otherTodosInSameCategory
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}
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