mirror of
https://github.com/ClickHouse/ClickHouse.git
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Merge pull request #21304 from amosbird/indexhint
Resurrect indexHint function.
This commit is contained in:
Nikita Mikhaylov
GitHub
commit
d4e8f9676b
@ -1192,6 +1192,109 @@ SELECT defaultValueOfTypeName('Nullable(Int8)')
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└──────────────────────────────────────────┘
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```
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## indexHint {#indexhint}
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The function is intended for debugging and introspection purposes. The function ignores it's argument and always returns 1. Arguments are not even evaluated.
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But for the purpose of index analysis, the argument of this function is analyzed as if it was present directly without being wrapped inside `indexHint` function. This allows to select data in index ranges by the corresponding condition but without further filtering by this condition. The index in ClickHouse is sparse and using `indexHint` will yield more data than specifying the same condition directly.
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**Syntax**
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```sql
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SELECT * FROM table WHERE indexHint(<expression>)
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```
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**Returned value**
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1. Type: [Uint8](https://clickhouse.yandex/docs/en/data_types/int_uint/#diapazony-uint).
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**Example**
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Here is the example of test data from the table [ontime](../../getting-started/example-datasets/ontime.md).
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Input table:
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```sql
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SELECT count() FROM ontime
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```
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```text
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┌─count()─┐
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│ 4276457 │
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└─────────┘
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```
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The table has indexes on the fields `(FlightDate, (Year, FlightDate))`.
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Create a query, where the index is not used.
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Query:
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```sql
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SELECT FlightDate AS k, count() FROM ontime GROUP BY k ORDER BY k
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```
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ClickHouse processed the entire table (`Processed 4.28 million rows`).
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Result:
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```text
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┌──────────k─┬─count()─┐
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│ 2017-01-01 │ 13970 │
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│ 2017-01-02 │ 15882 │
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........................
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│ 2017-09-28 │ 16411 │
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│ 2017-09-29 │ 16384 │
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│ 2017-09-30 │ 12520 │
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└────────────┴─────────┘
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```
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To apply the index, select a specific date.
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Query:
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```sql
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SELECT FlightDate AS k, count() FROM ontime WHERE k = '2017-09-15' GROUP BY k ORDER BY k
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```
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By using the index, ClickHouse processed a significantly smaller number of rows (`Processed 32.74 thousand rows`).
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Result:
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```text
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┌──────────k─┬─count()─┐
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│ 2017-09-15 │ 16428 │
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└────────────┴─────────┘
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```
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Now wrap the expression `k = '2017-09-15'` into `indexHint` function.
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Query:
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```sql
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SELECT
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FlightDate AS k,
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count()
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FROM ontime
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WHERE indexHint(k = '2017-09-15')
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GROUP BY k
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ORDER BY k ASC
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```
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ClickHouse used the index in the same way as the previous time (`Processed 32.74 thousand rows`).
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The expression `k = '2017-09-15'` was not used when generating the result.
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In examle the `indexHint` function allows to see adjacent dates.
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Result:
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```text
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┌──────────k─┬─count()─┐
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│ 2017-09-14 │ 7071 │
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│ 2017-09-15 │ 16428 │
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│ 2017-09-16 │ 1077 │
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│ 2017-09-30 │ 8167 │
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└────────────┴─────────┘
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```
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## replicate {#other-functions-replicate}
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Creates an array with a single value.
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@ -1133,6 +1133,111 @@ SELECT defaultValueOfTypeName('Nullable(Int8)')
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└──────────────────────────────────────────┘
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```
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## indexHint {#indexhint}
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Возвращает все данные из диапазона, в который попадают данные, соответствующие указанному выражению.
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Переданное выражение не будет вычислено. Выбор диапазона производится по индексу.
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Индекс в ClickHouse разреженный, при чтении диапазона в ответ попадают «лишние» соседние данные.
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**Синтаксис**
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```sql
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SELECT * FROM table WHERE indexHint(<expression>)
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```
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**Возвращаемое значение**
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Возвращает диапазон индекса, в котором выполняется заданное условие.
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Тип: [Uint8](https://clickhouse.yandex/docs/ru/data_types/int_uint/#diapazony-uint).
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**Пример**
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Рассмотрим пример с использованием тестовых данных таблицы [ontime](../../getting-started/example-datasets/ontime.md).
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Исходная таблица:
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```sql
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SELECT count() FROM ontime
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```
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```text
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┌─count()─┐
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│ 4276457 │
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└─────────┘
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```
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В таблице есть индексы по полям `(FlightDate, (Year, FlightDate))`.
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Выполним выборку по дате, где индекс не используется.
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Запрос:
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```sql
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SELECT FlightDate AS k, count() FROM ontime GROUP BY k ORDER BY k
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```
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ClickHouse обработал всю таблицу (`Processed 4.28 million rows`).
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Результат:
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```text
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┌──────────k─┬─count()─┐
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│ 2017-01-01 │ 13970 │
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│ 2017-01-02 │ 15882 │
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........................
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│ 2017-09-28 │ 16411 │
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│ 2017-09-29 │ 16384 │
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│ 2017-09-30 │ 12520 │
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└────────────┴─────────┘
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```
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Для подключения индекса выбираем конкретную дату.
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Запрос:
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```sql
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SELECT FlightDate AS k, count() FROM ontime WHERE k = '2017-09-15' GROUP BY k ORDER BY k
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```
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При использовании индекса ClickHouse обработал значительно меньшее количество строк (`Processed 32.74 thousand rows`).
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Результат:
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```text
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┌──────────k─┬─count()─┐
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│ 2017-09-15 │ 16428 │
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└────────────┴─────────┘
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```
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Передадим в функцию `indexHint` выражение `k = '2017-09-15'`.
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Запрос:
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```sql
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SELECT
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FlightDate AS k,
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count()
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FROM ontime
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WHERE indexHint(k = '2017-09-15')
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GROUP BY k
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ORDER BY k ASC
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```
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ClickHouse применил индекс по аналогии с примером выше (`Processed 32.74 thousand rows`).
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Выражение `k = '2017-09-15'` не используется при формировании результата.
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Функция `indexHint` позволяет увидеть соседние данные.
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Результат:
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```text
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┌──────────k─┬─count()─┐
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│ 2017-09-14 │ 7071 │
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│ 2017-09-15 │ 16428 │
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│ 2017-09-16 │ 1077 │
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│ 2017-09-30 │ 8167 │
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└────────────┴─────────┘
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```
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## replicate {#other-functions-replicate}
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Создает массив, заполненный одним значением.
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@ -477,6 +477,103 @@ FROM
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1 rows in set. Elapsed: 0.002 sec.
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## indexHint {#indexhint}
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输出符合索引选择范围内的所有数据，同时不实用参数中的表达式进行过滤。
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传递给函数的表达式参数将不会被计算，但ClickHouse使用参数中的表达式进行索引过滤。
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**返回值**
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- 1。
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**示例**
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这是一个包含[ontime](../../getting-started/example-datasets/ontime.md)测试数据集的测试表。
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```
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SELECT count() FROM ontime
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┌─count()─┐
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│ 4276457 │
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└─────────┘
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```
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该表使用`(FlightDate, (Year, FlightDate))`作为索引。
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对该表进行如下的查询：
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```
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:) SELECT FlightDate AS k, count() FROM ontime GROUP BY k ORDER BY k
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SELECT
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FlightDate AS k,
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count()
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FROM ontime
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GROUP BY k
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ORDER BY k ASC
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┌──────────k─┬─count()─┐
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│ 2017-01-01 │ 13970 │
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│ 2017-01-02 │ 15882 │
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........................
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│ 2017-09-28 │ 16411 │
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│ 2017-09-29 │ 16384 │
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│ 2017-09-30 │ 12520 │
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└────────────┴─────────┘
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273 rows in set. Elapsed: 0.072 sec. Processed 4.28 million rows, 8.55 MB (59.00 million rows/s., 118.01 MB/s.)
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```
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在这个查询中，由于没有使用索引，所以ClickHouse将处理整个表的所有数据(`Processed 4.28 million rows`)。使用下面的查询尝试使用索引进行查询：
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```
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:) SELECT FlightDate AS k, count() FROM ontime WHERE k = '2017-09-15' GROUP BY k ORDER BY k
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SELECT
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FlightDate AS k,
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count()
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FROM ontime
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WHERE k = '2017-09-15'
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GROUP BY k
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ORDER BY k ASC
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┌──────────k─┬─count()─┐
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│ 2017-09-15 │ 16428 │
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└────────────┴─────────┘
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1 rows in set. Elapsed: 0.014 sec. Processed 32.74 thousand rows, 65.49 KB (2.31 million rows/s., 4.63 MB/s.)
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```
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在最后一行的显示中，通过索引ClickHouse处理的行数明显减少（`Processed 32.74 thousand rows`）。
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现在将表达式`k = '2017-09-15'`传递给`indexHint`函数：
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```
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:) SELECT FlightDate AS k, count() FROM ontime WHERE indexHint(k = '2017-09-15') GROUP BY k ORDER BY k
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SELECT
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FlightDate AS k,
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count()
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FROM ontime
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WHERE indexHint(k = '2017-09-15')
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GROUP BY k
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ORDER BY k ASC
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┌──────────k─┬─count()─┐
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│ 2017-09-14 │ 7071 │
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│ 2017-09-15 │ 16428 │
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│ 2017-09-16 │ 1077 │
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│ 2017-09-30 │ 8167 │
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└────────────┴─────────┘
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4 rows in set. Elapsed: 0.004 sec. Processed 32.74 thousand rows, 65.49 KB (8.97 million rows/s., 17.94 MB/s.)
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```
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对于这个请求，根据ClickHouse显示ClickHouse与上一次相同的方式应用了索引（`Processed 32.74 thousand rows`）。但是，最终返回的结果集中并没有根据`k = '2017-09-15'`表达式进行过滤结果。
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由于ClickHouse中使用稀疏索引，因此在读取范围时（本示例中为相邻日期），"额外"的数据将包含在索引结果中。使用`indexHint`函数可以查看到它们。
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## 复制 {#replicate}
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使用单个值填充一个数组。
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70
src/Functions/indexHint.cpp
Normal file
70
src/Functions/indexHint.cpp
Normal file
@ -0,0 +1,70 @@
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#include <Functions/IFunctionImpl.h>
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#include <Functions/FunctionFactory.h>
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#include <DataTypes/DataTypesNumber.h>
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namespace DB
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{
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/** The `indexHint` function takes any number of any arguments and always returns one.
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*
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* This function has a special meaning (see ExpressionAnalyzer, KeyCondition)
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* - the expressions inside it are not evaluated;
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* - but when analyzing the index (selecting ranges for reading), this function is treated the same way,
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* as if instead of using it the expression itself would be.
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*
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* Example: WHERE something AND indexHint(CounterID = 34)
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* - do not read or calculate CounterID = 34, but select ranges in which the CounterID = 34 expression can be true.
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*
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* The function can be used for debugging purposes, as well as for (hidden from the user) query conversions.
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*/
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class FunctionIndexHint : public IFunction
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{
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public:
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static constexpr auto name = "indexHint";
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static FunctionPtr create(ContextPtr)
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{
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return std::make_shared<FunctionIndexHint>();
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}
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bool isVariadic() const override
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{
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return true;
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}
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size_t getNumberOfArguments() const override
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{
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return 0;
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}
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bool useDefaultImplementationForNulls() const override { return false; }
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bool isSuitableForConstantFolding() const override { return false; }
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String getName() const override
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{
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return name;
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}
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DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const override
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{
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return std::make_shared<DataTypeUInt8>();
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}
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ColumnPtr executeImpl(const ColumnsWithTypeAndName &, const DataTypePtr &, size_t input_rows_count) const override
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{
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return DataTypeUInt8().createColumnConst(input_rows_count, 1u);
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}
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ColumnPtr getResultIfAlwaysReturnsConstantAndHasArguments(const ColumnsWithTypeAndName &) const override
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{
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return DataTypeUInt8().createColumnConst(1, 1u);
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}
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};
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void registerFunctionIndexHint(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionIndexHint>();
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}
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}
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@ -39,7 +39,7 @@ struct DivideIntegralByConstantImpl
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|
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static ResultType process(A a, B b) { return Op::template apply<ResultType>(a, b); }
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static NO_INLINE void vectorConstant(const A * __restrict a_pos, B b, ResultType * __restrict c_pos, size_t size)
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static void NO_INLINE NO_SANITIZE_UNDEFINED vectorConstant(const A * __restrict a_pos, B b, ResultType * __restrict c_pos, size_t size)
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{
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wsign-compare"
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@ -43,7 +43,7 @@ struct ModuloByConstantImpl
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|
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static ResultType process(A a, B b) { return Op::template apply<ResultType>(a, b); }
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static void NO_INLINE vectorConstant(const A * __restrict src, B b, ResultType * __restrict dst, size_t size)
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static void NO_INLINE NO_SANITIZE_UNDEFINED vectorConstant(const A * __restrict src, B b, ResultType * __restrict dst, size_t size)
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{
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wsign-compare"
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|
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@ -28,6 +28,7 @@ void registerFunctionSleep(FunctionFactory &);
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void registerFunctionSleepEachRow(FunctionFactory &);
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void registerFunctionMaterialize(FunctionFactory &);
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void registerFunctionIgnore(FunctionFactory &);
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void registerFunctionIndexHint(FunctionFactory &);
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void registerFunctionIdentity(FunctionFactory &);
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void registerFunctionArrayJoin(FunctionFactory &);
|
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void registerFunctionReplicate(FunctionFactory &);
|
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@ -101,6 +102,7 @@ void registerFunctionsMiscellaneous(FunctionFactory & factory)
|
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registerFunctionSleepEachRow(factory);
|
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registerFunctionMaterialize(factory);
|
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registerFunctionIgnore(factory);
|
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registerFunctionIndexHint(factory);
|
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registerFunctionIdentity(factory);
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registerFunctionArrayJoin(factory);
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registerFunctionReplicate(factory);
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@ -303,6 +303,7 @@ SRCS(
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ignore.cpp
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ilike.cpp
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in.cpp
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indexHint.cpp
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initializeAggregation.cpp
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intDiv.cpp
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intDivOrZero.cpp
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|
||||
@ -181,7 +181,7 @@ const ActionsDAG::Node & ActionsDAG::addFunction(
|
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}
|
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}
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/// Some functions like ignore() or getTypeName() always return constant result even if arguments are not constant.
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/// Some functions like ignore(), indexHint() or getTypeName() always return constant result even if arguments are not constant.
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/// We can't do constant folding, but can specify in sample block that function result is constant to avoid
|
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/// unnecessary materialization.
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if (!node.column && node.function_base->isSuitableForConstantFolding())
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@ -811,6 +811,14 @@ void ActionsMatcher::visit(const ASTFunction & node, const ASTPtr & ast, Data &
|
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}
|
||||
}
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||||
|
||||
/// A special function `indexHint`. Everything that is inside it is not calculated
|
||||
if (node.name == "indexHint")
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{
|
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// Arguments are removed. We add function instead of constant column to avoid constant folding.
|
||||
data.addFunction(FunctionFactory::instance().get("indexHint", data.getContext()), {}, column_name);
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||||
return;
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||||
}
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||||
|
||||
if (node.is_window_function)
|
||||
{
|
||||
// Also add columns from PARTITION BY and ORDER BY of window functions.
|
||||
|
||||
@ -51,8 +51,10 @@ bool RequiredSourceColumnsMatcher::needChildVisit(const ASTPtr & node, const AST
|
||||
|
||||
if (const auto * f = node->as<ASTFunction>())
|
||||
{
|
||||
/// "indexHint" is a special function for index analysis.
|
||||
/// Everything that is inside it is not calculated. See KeyCondition
|
||||
/// "lambda" visit children itself.
|
||||
if (f->name == "lambda")
|
||||
if (f->name == "indexHint" || f->name == "lambda")
|
||||
return false;
|
||||
}
|
||||
|
||||
|
||||
@ -309,11 +309,11 @@ static const std::map<std::string, std::string> inverse_relations = {
|
||||
|
||||
bool isLogicalOperator(const String & func_name)
|
||||
{
|
||||
return (func_name == "and" || func_name == "or" || func_name == "not");
|
||||
return (func_name == "and" || func_name == "or" || func_name == "not" || func_name == "indexHint");
|
||||
}
|
||||
|
||||
/// The node can be one of:
|
||||
/// - Logical operator (AND, OR, NOT)
|
||||
/// - Logical operator (AND, OR, NOT and indexHint() - logical NOOP)
|
||||
/// - An "atom" (relational operator, constant, expression)
|
||||
/// - A logical constant expression
|
||||
/// - Any other function
|
||||
@ -330,7 +330,8 @@ ASTPtr cloneASTWithInversionPushDown(const ASTPtr node, const bool need_inversio
|
||||
|
||||
const auto result_node = makeASTFunction(func->name);
|
||||
|
||||
if (need_inversion)
|
||||
/// indexHint() is a special case - logical NOOP function
|
||||
if (result_node->name != "indexHint" && need_inversion)
|
||||
{
|
||||
result_node->name = (result_node->name == "and") ? "or" : "and";
|
||||
}
|
||||
@ -965,6 +966,8 @@ bool KeyCondition::isKeyPossiblyWrappedByMonotonicFunctions(
|
||||
{
|
||||
const auto & args = (*it)->arguments->children;
|
||||
auto func_builder = FunctionFactory::instance().tryGet((*it)->name, context);
|
||||
if (!func_builder)
|
||||
return false;
|
||||
ColumnsWithTypeAndName arguments;
|
||||
ColumnWithTypeAndName const_arg;
|
||||
FunctionWithOptionalConstArg::Kind kind = FunctionWithOptionalConstArg::Kind::NO_CONST;
|
||||
@ -1277,6 +1280,8 @@ bool KeyCondition::tryParseAtomFromAST(const ASTPtr & node, ContextPtr context,
|
||||
bool KeyCondition::tryParseLogicalOperatorFromAST(const ASTFunction * func, RPNElement & out)
|
||||
{
|
||||
/// Functions AND, OR, NOT.
|
||||
/// Also a special function `indexHint` - works as if instead of calling a function there are just parentheses
|
||||
/// (or, the same thing - calling the function `and` from one argument).
|
||||
const ASTs & args = func->arguments->children;
|
||||
|
||||
if (func->name == "not")
|
||||
@ -1288,7 +1293,7 @@ bool KeyCondition::tryParseLogicalOperatorFromAST(const ASTFunction * func, RPNE
|
||||
}
|
||||
else
|
||||
{
|
||||
if (func->name == "and")
|
||||
if (func->name == "and" || func->name == "indexHint")
|
||||
out.function = RPNElement::FUNCTION_AND;
|
||||
else if (func->name == "or")
|
||||
out.function = RPNElement::FUNCTION_OR;
|
||||
|
||||
@ -39,7 +39,6 @@
|
||||
#include <DataTypes/DataTypeUUID.h>
|
||||
#include <DataTypes/DataTypesNumber.h>
|
||||
#include <Storages/VirtualColumnUtils.h>
|
||||
#include <DataStreams/materializeBlock.h>
|
||||
|
||||
namespace ProfileEvents
|
||||
{
|
||||
|
||||
@ -392,7 +392,7 @@ bool MergeTreeIndexConditionSet::operatorFromAST(ASTPtr & node)
|
||||
|
||||
func->name = "__bitSwapLastTwo";
|
||||
}
|
||||
else if (func->name == "and")
|
||||
else if (func->name == "and" || func->name == "indexHint")
|
||||
{
|
||||
auto last_arg = args.back();
|
||||
args.pop_back();
|
||||
@ -448,7 +448,7 @@ bool MergeTreeIndexConditionSet::checkASTUseless(const ASTPtr & node, bool atomi
|
||||
|
||||
const ASTs & args = func->arguments->children;
|
||||
|
||||
if (func->name == "and")
|
||||
if (func->name == "and" || func->name == "indexHint")
|
||||
return checkASTUseless(args[0], atomic) && checkASTUseless(args[1], atomic);
|
||||
else if (func->name == "or")
|
||||
return checkASTUseless(args[0], atomic) || checkASTUseless(args[1], atomic);
|
||||
|
||||
@ -339,6 +339,10 @@ bool MergeTreeWhereOptimizer::cannotBeMoved(const ASTPtr & ptr, bool is_final) c
|
||||
if ("globalIn" == function_ptr->name
|
||||
|| "globalNotIn" == function_ptr->name)
|
||||
return true;
|
||||
|
||||
/// indexHint is a special function that it does not make sense to transfer to PREWHERE
|
||||
if ("indexHint" == function_ptr->name)
|
||||
return true;
|
||||
}
|
||||
else if (auto opt_name = IdentifierSemantic::getColumnName(ptr))
|
||||
{
|
||||
|
||||
@ -90,6 +90,8 @@ private:
|
||||
bool operatorFromAST(const ASTFunction * func, RPNElement & out)
|
||||
{
|
||||
/// Functions AND, OR, NOT.
|
||||
/// Also a special function `indexHint` - works as if instead of calling a function there are just parentheses
|
||||
/// (or, the same thing - calling the function `and` from one argument).
|
||||
const ASTs & args = typeid_cast<const ASTExpressionList &>(*func->arguments).children;
|
||||
|
||||
if (func->name == "not")
|
||||
@ -101,7 +103,7 @@ private:
|
||||
}
|
||||
else
|
||||
{
|
||||
if (func->name == "and")
|
||||
if (func->name == "and" || func->name == "indexHint")
|
||||
out.function = RPNElement::FUNCTION_AND;
|
||||
else if (func->name == "or")
|
||||
out.function = RPNElement::FUNCTION_OR;
|
||||
|
||||
35
tests/queries/0_stateless/01739_index_hint.reference
Normal file
35
tests/queries/0_stateless/01739_index_hint.reference
Normal file
@ -0,0 +1,35 @@
|
||||
-- { echo }
|
||||
|
||||
drop table if exists tbl;
|
||||
create table tbl (p Int64, t Int64, f Float64) Engine=MergeTree partition by p order by t settings index_granularity=1;
|
||||
insert into tbl select number / 4, number, 0 from numbers(16);
|
||||
select * from tbl WHERE indexHint(t = 1) order by t;
|
||||
0 0 0
|
||||
0 1 0
|
||||
select * from tbl WHERE indexHint(t in (select toInt64(number) + 2 from numbers(3))) order by t;
|
||||
0 1 0
|
||||
0 2 0
|
||||
0 3 0
|
||||
1 4 0
|
||||
select * from tbl WHERE indexHint(p = 2) order by t;
|
||||
2 8 0
|
||||
2 9 0
|
||||
2 10 0
|
||||
2 11 0
|
||||
select * from tbl WHERE indexHint(p in (select toInt64(number) - 2 from numbers(3))) order by t;
|
||||
0 0 0
|
||||
0 1 0
|
||||
0 2 0
|
||||
0 3 0
|
||||
drop table tbl;
|
||||
drop table if exists XXXX;
|
||||
create table XXXX (t Int64, f Float64) Engine=MergeTree order by t settings index_granularity=128;
|
||||
insert into XXXX select number*60, 0 from numbers(100000);
|
||||
SELECT count() FROM XXXX WHERE indexHint(t = 42);
|
||||
128
|
||||
drop table if exists XXXX;
|
||||
create table XXXX (t Int64, f Float64) Engine=MergeTree order by t settings index_granularity=8192;
|
||||
insert into XXXX select number*60, 0 from numbers(100000);
|
||||
SELECT count() FROM XXXX WHERE indexHint(t = toDateTime(0));
|
||||
100000
|
||||
drop table XXXX;
|
||||
35
tests/queries/0_stateless/01739_index_hint.sql
Normal file
35
tests/queries/0_stateless/01739_index_hint.sql
Normal file
@ -0,0 +1,35 @@
|
||||
-- { echo }
|
||||
|
||||
drop table if exists tbl;
|
||||
|
||||
create table tbl (p Int64, t Int64, f Float64) Engine=MergeTree partition by p order by t settings index_granularity=1;
|
||||
|
||||
insert into tbl select number / 4, number, 0 from numbers(16);
|
||||
|
||||
select * from tbl WHERE indexHint(t = 1) order by t;
|
||||
|
||||
select * from tbl WHERE indexHint(t in (select toInt64(number) + 2 from numbers(3))) order by t;
|
||||
|
||||
select * from tbl WHERE indexHint(p = 2) order by t;
|
||||
|
||||
select * from tbl WHERE indexHint(p in (select toInt64(number) - 2 from numbers(3))) order by t;
|
||||
|
||||
drop table tbl;
|
||||
|
||||
drop table if exists XXXX;
|
||||
|
||||
create table XXXX (t Int64, f Float64) Engine=MergeTree order by t settings index_granularity=128;
|
||||
|
||||
insert into XXXX select number*60, 0 from numbers(100000);
|
||||
|
||||
SELECT count() FROM XXXX WHERE indexHint(t = 42);
|
||||
|
||||
drop table if exists XXXX;
|
||||
|
||||
create table XXXX (t Int64, f Float64) Engine=MergeTree order by t settings index_granularity=8192;
|
||||
|
||||
insert into XXXX select number*60, 0 from numbers(100000);
|
||||
|
||||
SELECT count() FROM XXXX WHERE indexHint(t = toDateTime(0));
|
||||
|
||||
drop table XXXX;
|
||||
Loading…
Reference in New Issue
Block a user