ignore_* 会话设置

ClickHouse 在 ignore_* 生成分组中的会话设置。

这些设置可在 system.settings 中找到，并由 源代码 自动生成。

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ignore_cold_parts_seconds

仅在 ClickHouse Cloud 中生效。在新的数据分区片段被预热 (参见 cache_populated_by_fetch) 或达到指定秒数之前，会将其排除在 SELECT 查询之外。仅适用于 Replicated-/SharedMergeTree。

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ignore_data_skipping_indices

如果查询会使用指定的跳过索引，则忽略这些索引。

请看下面的示例：

CREATE TABLE data
(
    key Int,
    x Int,
    y Int,
    INDEX x_idx x TYPE minmax GRANULARITY 1,
    INDEX y_idx y TYPE minmax GRANULARITY 1,
    INDEX xy_idx (x,y) TYPE minmax GRANULARITY 1
)
Engine=MergeTree()
ORDER BY key;

INSERT INTO data VALUES (1, 2, 3);

SELECT * FROM data;
SELECT * FROM data SETTINGS ignore_data_skipping_indices=''; -- query will produce CANNOT_PARSE_TEXT error.
SELECT * FROM data SETTINGS ignore_data_skipping_indices='x_idx'; -- Ok.
SELECT * FROM data SETTINGS ignore_data_skipping_indices='na_idx'; -- Ok.

SELECT * FROM data WHERE x = 1 AND y = 1 SETTINGS ignore_data_skipping_indices='xy_idx',force_data_skipping_indices='xy_idx' ; -- query will produce INDEX_NOT_USED error, since xy_idx is explicitly ignored.
SELECT * FROM data WHERE x = 1 AND y = 2 SETTINGS ignore_data_skipping_indices='xy_idx';

不忽略任何索引时的查询：

EXPLAIN indexes = 1 SELECT * FROM data WHERE x = 1 AND y = 2;

Expression ((Projection + Before ORDER BY))
  Filter (WHERE)
    ReadFromMergeTree (default.data)
    Indexes:
      PrimaryKey
        Condition: true
        Parts: 1/1
        Granules: 1/1
      Skip
        Name: x_idx
        Description: minmax GRANULARITY 1
        Parts: 0/1
        Granules: 0/1
      Skip
        Name: y_idx
        Description: minmax GRANULARITY 1
        Parts: 0/0
        Granules: 0/0
      Skip
        Name: xy_idx
        Description: minmax GRANULARITY 1
        Parts: 0/0
        Granules: 0/0

忽略 xy_idx 索引：

EXPLAIN indexes = 1 SELECT * FROM data WHERE x = 1 AND y = 2 SETTINGS ignore_data_skipping_indices='xy_idx';

Expression ((Projection + Before ORDER BY))
  Filter (WHERE)
    ReadFromMergeTree (default.data)
    Indexes:
      PrimaryKey
        Condition: true
        Parts: 1/1
        Granules: 1/1
      Skip
        Name: x_idx
        Description: minmax GRANULARITY 1
        Parts: 0/1
        Granules: 0/1
      Skip
        Name: y_idx
        Description: minmax GRANULARITY 1
        Parts: 0/0
        Granules: 0/0

适用于 MergeTree 家族中的表。

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ignore_drop_queries_probability

如果启用，服务器将以指定的概率忽略所有 DROP 表查询 (对于 Memory 和 JOIN 引擎，会将 DROP 替换为 TRUNCATE) 。用于测试目的

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ignore_format_null_for_explain

如果启用，EXPLAIN 查询中的 FORMAT Null 将被忽略，改为使用默认输出格式。 如果禁用，带有 FORMAT Null 的 EXPLAIN 查询将不会产生任何输出 (向后兼容行为) 。

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ignore_materialized_views_with_dropped_target_table

在推送到视图时，忽略目标表已被删除的 MV