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Enhance subscriptions to not emit updates when the underlying databas…
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…e value has not changed

Fix unsubscribe (dispose) for queries
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@tp
tp committed Oct 23, 2024
1 parent e8d03b0 commit 919e97d
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6 changes: 6 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,3 +1,9 @@
## 1.4.0

* Enhance subscriptions to not emit updates when the underlying database value has not changed
* E.g. when an object is updated with the exact same storage values or a query ends up with the same result list no updates are emitted
* Fix unsubscribe for queries

## 1.3.0

* Add `single`/`singleOnce` for cases where one expects a single match, but does not have a primary key
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111 changes: 86 additions & 25 deletions lib/src/index_entity_store.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ part 'index_columns.dart';
part 'query.dart';
part 'query_result.dart';

typedef QueryResultMapping<T> = (T Function(), QueryResult<T>);
typedef QueryResultMapping<T> = (MappedDBResult<T> Function(), QueryResult<T>);

enum SortOrder {
asc,
Expand Down Expand Up @@ -45,16 +45,17 @@ class IndexedEntityStore<T, K> {
final List<QueryResultMapping> _entityResults = [];

@visibleForTesting
int get subscriptionCount =>
_singleEntityResults.values.expand((mappings) => mappings).length +
_entityResults.length;
int get subscriptionCount {
return _singleEntityResults.values.expand((mappings) => mappings).length +
_entityResults.length;
}

/// Returns a subscription to a single entity by its primary key
QueryResult<T?> get(K key) {
final QueryResultMapping<T?> mapping = (
() => getOnce(key),
() => _getOnce(key),
QueryResult._(
initialValue: getOnce(key),
initialValue: _getOnce(key),
onDispose: (r) {
_singleEntityResults[key] = _singleEntityResults[key]!
.where((mapping) => mapping.$2 != r)
Expand All @@ -74,28 +75,34 @@ class IndexedEntityStore<T, K> {

/// Returns a single entity by its primary key
T? getOnce(K key) {
return _getOnce(key).result;
}

MappedDBResult<T?> _getOnce(K key) {
final res = _database.select(
'SELECT value FROM `entity` WHERE `type` = ? AND `key` = ?',
[_entityKey, key],
);

if (res.isEmpty) {
return null;
return (dbValues: [null], result: null);
}

return _connector.deserialize(res.single['value']);
final dbValue = res.single['value'];

return (dbValues: [dbValue], result: _connector.deserialize(dbValue));
}

/// Returns a subscription to all entities in this store
QueryResult<List<T>> getAll({
OrderByClause? orderBy,
}) {
final QueryResultMapping<List<T>> mapping = (
() => getAllOnce(orderBy: orderBy),
() => _getAllOnce(orderBy: orderBy),
QueryResult._(
initialValue: getAllOnce(orderBy: orderBy),
initialValue: _getAllOnce(orderBy: orderBy),
onDispose: (r) {
_entityResults.removeWhere((m) => m.$2 != r);
_entityResults.removeWhere((m) => m.$2 == r);
},
)
);
Expand All @@ -108,6 +115,12 @@ class IndexedEntityStore<T, K> {
/// Returns a list of all entities in this store
List<T> getAllOnce({
OrderByClause? orderBy,
}) {
return _getAllOnce(orderBy: orderBy).result;
}

MappedDBResult<List<T>> _getAllOnce({
OrderByClause? orderBy,
}) {
final res = _database.select(
[
Expand All @@ -124,7 +137,12 @@ class IndexedEntityStore<T, K> {
],
);

return res.map((e) => _connector.deserialize(e['value'])).toList();
final values = res.map((e) => e['value']).toList();

return (
dbValues: values,
result: values.map((v) => _connector.deserialize(v)).toList()
);
}

/// Returns the single entity (or null) for the given query
Expand All @@ -134,11 +152,11 @@ class IndexedEntityStore<T, K> {
/// they can use [query] with a limit instead.
QueryResult<T?> single(QueryBuilder q) {
final QueryResultMapping<T?> mapping = (
() => singleOnce(q),
() => _singleOnce(q),
QueryResult._(
initialValue: singleOnce(q),
initialValue: _singleOnce(q),
onDispose: (r) {
_entityResults.removeWhere((m) => m.$2 != r);
_entityResults.removeWhere((m) => m.$2 == r);
},
)
);
Expand All @@ -154,14 +172,19 @@ class IndexedEntityStore<T, K> {
/// If the caller expects more than 1 value but is only interested in one,
/// they can use [query] with a limit instead.
T? singleOnce(QueryBuilder q) {
final result = queryOnce(q, limit: 2);
return _singleOnce(q).result;
}

MappedDBResult<T?> _singleOnce(QueryBuilder q) {
final result = _queryOnce(q, limit: 2);

if (result.length > 1) {
if (result.result.length > 1) {
throw Exception(
'singleOnce expected to find one element, but found at least 2 matching the query $q');
'singleOnce expected to find one element, but found at least 2 matching the query $q',
);
}

return result.singleOrNull;
return (dbValues: result.dbValues, result: result.result.firstOrNull);
}

/// Returns a subscription to entities matching the given query
Expand All @@ -171,11 +194,11 @@ class IndexedEntityStore<T, K> {
int? limit,
}) {
final QueryResultMapping<List<T>> mapping = (
() => queryOnce(q, limit: limit, orderBy: orderBy),
() => _queryOnce(q, limit: limit, orderBy: orderBy),
QueryResult._(
initialValue: queryOnce(q, limit: limit, orderBy: orderBy),
initialValue: _queryOnce(q, limit: limit, orderBy: orderBy),
onDispose: (r) {
_entityResults.removeWhere((m) => m.$2 != r);
_entityResults.removeWhere((m) => m.$2 == r);
},
)
);
Expand All @@ -190,6 +213,14 @@ class IndexedEntityStore<T, K> {
QueryBuilder q, {
OrderByClause? orderBy,
int? limit,
}) {
return _queryOnce(q, orderBy: orderBy, limit: limit).result;
}

MappedDBResult<List<T>> _queryOnce(
QueryBuilder q, {
OrderByClause? orderBy,
int? limit,
}) {
final (w, s) = q(_indexColumns)._entityKeysQuery();

Expand All @@ -211,7 +242,12 @@ class IndexedEntityStore<T, K> {

final res = _database.select(query, values);

return res.map((e) => _connector.deserialize(e['value'])).toList();
final dbValues = res.map((e) => e['value']).toList();

return (
dbValues: dbValues,
result: dbValues.map((v) => _connector.deserialize(v)).toList(),
);
}

void insert(T e) {
Expand Down Expand Up @@ -257,6 +293,14 @@ class IndexedEntityStore<T, K> {
delete(_connector.getPrimaryKey(entity));
}

void deleteEntities(Iterable<T> entities) {
deleteMany(
{
for (final e in entities) _connector.getPrimaryKey(e),
},
);
}

void deleteMany(Set<K> keys) {
for (final key in keys) {
_database.execute(
Expand Down Expand Up @@ -307,13 +351,30 @@ class IndexedEntityStore<T, K> {
final singleEntitySubscriptions = _singleEntityResults[key];
if (singleEntitySubscriptions != null) {
for (final mapping in singleEntitySubscriptions) {
mapping.$2._value.value = mapping.$1();
final newValue = mapping.$1();

if (newValue.dbValues.length ==
mapping.$2._value.value.dbValues.length &&
newValue.dbValues.indexed.every(
(e) => mapping.$2._value.value.dbValues[e.$1] == e.$2)) {
continue; // values already match
}

mapping.$2._value.value = newValue;
}
}
}

for (final mapping in _entityResults) {
mapping.$2._value.value = mapping.$1();
final newValue = mapping.$1();

if (newValue.dbValues.length == mapping.$2._value.value.dbValues.length &&
newValue.dbValues.indexed
.every((e) => mapping.$2._value.value.dbValues[e.$1] == e.$2)) {
continue; // values already match
}

mapping.$2._value.value = newValue;
}
}
}
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8 changes: 5 additions & 3 deletions lib/src/query_result.dart
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Original file line number Diff line number Diff line change
@@ -1,13 +1,15 @@
part of 'index_entity_store.dart';

typedef MappedDBResult<T> = ({List<dynamic> dbValues, T result});

class QueryResult<T> implements ValueListenable<T> {
QueryResult._({
required T initialValue,
required MappedDBResult<T> initialValue,
void Function(QueryResult<T> self)? onDispose,
}) : _value = ValueNotifier(initialValue),
_onDispose = onDispose;

final ValueNotifier<T> _value;
final ValueNotifier<MappedDBResult<T>> _value;

final void Function(QueryResult<T> self)? _onDispose;

Expand All @@ -22,7 +24,7 @@ class QueryResult<T> implements ValueListenable<T> {
}

@override
T get value => _value.value;
T get value => _value.value.result;

@mustCallSuper
void dispose() {
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2 changes: 1 addition & 1 deletion pubspec.yaml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name: indexed_entity_store
description: A fast, simple, and synchronous entity store for Flutter applications.
version: 1.3.0
version: 1.4.0
repository: https://github.com/LunaONE/indexed_entity_store

environment:
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