Merge pull request #17855 from spongedu/complete_sysemlog_table_doc

1. Refine documents for system log table; 2. fix a link error in config.xml

docs/en/operations/system-tables/index.md

@@ -20,7 +20,33 @@ System tables:
 
 Most of system tables store their data in RAM. A ClickHouse server creates such system tables at the start.
 
-Unlike other system tables, the system tables [metric_log](../../operations/system-tables/metric_log.md#system_tables-metric_log), [query_log](../../operations/system-tables/query_log.md#system_tables-query_log), [query_thread_log](../../operations/system-tables/query_thread_log.md#system_tables-query_thread_log), [trace_log](../../operations/system-tables/trace_log.md#system_tables-trace_log) are served by [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) table engine and store their data in a storage filesystem. If you remove a table from a filesystem, the ClickHouse server creates the empty one again at the time of the next data writing. If system table schema changed in a new release, then ClickHouse renames the current table and creates a new one.
+Unlike other system tables, the system log tables [metric_log](../../operations/system-tables/metric_log.md), [query_log](../../operations/system-tables/query_log.md), [query_thread_log](../../operations/system-tables/query_thread_log.md), [trace_log](../../operations/system-tables/trace_log.md), [part_log](../../operations/system-tables/part_log.md), crash_log and [text_log](../../operations/system-tables/text_log.md) are served by [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) table engine and store their data in a storage filesystem by default. If you remove a table from a filesystem, the ClickHouse server creates the empty one again at the time of the next data writing. If system table schema changed in a new release, then ClickHouse renames the current table and creates a new one.
+
+System log tables can be customized by creating a config file with the same name as the table under `/etc/clickhouse-server/config.d/`, or setting corresponding elements in `/etc/clickhouse-server/config.xml`. Elements can be customized are:
+
+-   `database`: database the system log table belongs to. This option is deprecated now. All system log tables are under database `system`.
+-   `table`: table to insert data.
+-   `partition_by`: specify [PARTITION BY](../../engines/table-engines/mergetree-family/custom-partitioning-key.md) expression.
+-   `ttl`: specify table [TTL](../../sql-reference/statements/alter/ttl.md) expression.
+-   `flush_interval_milliseconds`: interval of flushing data to disk.
+-   `engine`: provide full engine expression (starting with `ENGINE =` ) with parameters. This option is contradict with `partition_by` and `ttl`. If set together, the server would raise an exception and exit.
+
+An example:
+
+```
+<yandex>
+    <query_log>
+        <database>system</database>
+        <table>query_log</table>
+        <partition_by>toYYYYMM(event_date)</partition_by>
+        <ttl>event_date + INTERVAL 30 DAY DELETE</ttl>
+        <!--
+        <engine>ENGINE = MergeTree PARTITION BY toYYYYMM(event_date) ORDER BY (event_date, event_time) SETTINGS index_granularity = 1024</engine>
+        -->
+        <flush_interval_milliseconds>7500</flush_interval_milliseconds>
+    </query_log>
+</yandex>
+```
 
 By default, table growth is unlimited. To control a size of a table, you can use [TTL](../../sql-reference/statements/alter/ttl.md#manipulations-with-table-ttl) settings for removing outdated log records. Also you can use the partitioning feature of `MergeTree`-engine tables.
 

docs/zh/operations/system-tables/index.md

@@ -22,9 +22,35 @@ toc_title: "\u7CFB\u7EDF\u8868"
 
 大多数系统表将数据存储在RAM中。 ClickHouse服务器在开始时创建此类系统表。
 
-与其他系统表不同，系统表 [metric_log](../../operations/system-tables/metric_log.md#system_tables-metric_log), [query_log](../../operations/system-tables/query_log.md#system_tables-query_log), [query_thread_log](../../operations/system-tables/query_thread_log.md#system_tables-query_thread_log), [trace_log](../../operations/system-tables/trace_log.md#system_tables-trace_log) 由 [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) 表引擎并将其数据存储在存储文件系统中。 如果从文件系统中删除表，ClickHouse服务器会在下一次写入数据时再次创建空表。 如果系统表架构在新版本中发生更改，则ClickHouse会重命名当前表并创建一个新表。
+与其他系统表不同，系统日志表 [metric_log](../../operations/system-tables/metric_log.md#system_tables-metric_log), [query_log](../../operations/system-tables/query_log.md#system_tables-query_log), [query_thread_log](../../operations/system-tables/query_thread_log.md#system_tables-query_thread_log), [trace_log](../../operations/system-tables/trace_log.md#system_tables-trace_log), [part_log](../../operations/system-tables/part_log.md#system.part_log), crash_log and text_log 默认采用[MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) 引擎并将其数据存储在存储文件系统中。 如果从文件系统中删除表，ClickHouse服务器会在下一次写入数据时再次创建空表。 如果系统表架构在新版本中发生更改，则ClickHouse会重命名当前表并创建一个新表。
 
-默认情况下，表增长是无限的。 要控制表的大小，可以使用 [TTL](../../sql-reference/statements/alter.md#manipulations-with-table-ttl) 删除过期日志记录的设置。 你也可以使用分区功能 `MergeTree`-发动机表。
+用户可以通过在`/etc/clickhouse-server/config.d/`下创建与系统表同名的配置文件, 或者在`/etc/clickhouse-server/config.xml`中设置相应配置项，来自定义系统日志表的结构。可以自定义的配置项如下:
+
+-   `database`: 系统日志表所在的数据库。这个选项目前已经废弃。所有的系统日表都位于`system`库中。
+-   `table`: 系统日志表名。
+-   `partition_by`: 指定[PARTITION BY](../../engines/table-engines/mergetree-family/custom-partitioning-key.md)表达式。
+-   `ttl`: 指定系统日志表TTL选项。
+-   `flush_interval_milliseconds`: 指定系统日志表数据落盘时间。
+-   `engine`: 指定完整的表引擎定义。(以`ENGINE = `开始)。 这个选项与`partition_by`以及`ttl`冲突。如果两者一起设置，服务启动时会抛出异常并且退出。
+
+一个配置定义的例子如下：
+
+```
+<yandex>
+    <query_log>
+        <database>system</database>
+        <table>query_log</table>
+        <partition_by>toYYYYMM(event_date)</partition_by>
+        <ttl>event_date + INTERVAL 30 DAY DELETE</ttl>
+        <!--
+        <engine>ENGINE = MergeTree PARTITION BY toYYYYMM(event_date) ORDER BY (event_date, event_time) SETTINGS index_granularity = 1024</engine>
+        -->
+        <flush_interval_milliseconds>7500</flush_interval_milliseconds>
+    </query_log>
+</yandex>
+```
+
+默认情况下，表增长是无限的。 要控制表的大小，可以使用 TTL 删除过期日志记录的设置。 你也可以使用分区功能 `MergeTree`-发动机表。
 
 ## 系统指标的来源 {#system-tables-sources-of-system-metrics}
 

programs/server/config.xml

@@ -676,7 +676,7 @@
         <database>system</database>
         <table>query_log</table>
         <!--
-            PARTITION BY expr: https://clickhouse.yandex/docs/en/table_engines/custom_partitioning_key/
+            PARTITION BY expr: https://clickhouse.yandex/docs/en/table_engines/mergetree-family/custom_partitioning_key/
             Example:
                 event_date
                 toMonday(event_date)