add the function directory

docs/nightly/en/faq-and-others/faq.md

@@ -145,7 +145,7 @@ Of course, please use the `compact_table` function:
 select compact_table("test");
 ```
 
-There are many [administration functions](/reference/sql/functions#admin-functions) for database management.
+There are many [administration functions](/reference/sql/functions/overview#admin-functions) for database management.
 
 ### Can GreptimeDB be used to store logs?
 

docs/nightly/en/reference/sql/functions/overview.md

@@ -249,7 +249,7 @@ select database();
 GreptimeDB provides some administration functions to manage the database and data:
 
 * `flush_table(table_name)` to flush a table's memtables into SST file by table name.
-* `flush_region(region_id)` to flush a region's memtables into SST file by region id. Find the region id through [PARTITIONS](./information-schema/partitions.md) table.
+* `flush_region(region_id)` to flush a region's memtables into SST file by region id. Find the region id through [PARTITIONS](../information-schema/partitions.md) table.
 * `compact_table(table_name)` to schedule a compaction task for a table by table name.
 * `compact_region(region_id)` to schedule a compaction task for a region by region id.
 * `migrate_region(region_id, from_peer, to_peer, [timeout])` to migrate regions between datanodes, please read the [Region Migration](/user-guide/operations/region-migration).

docs/nightly/en/reference/sql/group_by.md

@@ -66,4 +66,4 @@ FROM system_metrics
 GROUP BY dt
 ```
 
-Please refer to [date_trunc](./functions.md#date_trunc) for more details.
+Please refer to [date_trunc](./functions/overview.md#date_trunc) for more details.

docs/nightly/en/reference/sql/overview.md

@@ -11,7 +11,7 @@
 * [GROUP BY](./group_by.md)
 * [LIMIT](./limit.md)
 * [JOIN](./join.md)
-* [Functions](./functions.md)
+* [Functions](./functions/overview.md)
 * [DELETE](./delete.md)
 * [SHOW](./show.md)
 * [TQL](./tql.md)

docs/nightly/en/reference/sql/range.md

@@ -24,7 +24,7 @@ INTERVAL :=  TIME_INTERVAL | ( INTERVAL expr )
    - Subkeyword `BY`, optional field, followed by parameter `(columna, columnb,..)`, describes the aggregate key. For legal `BY_OPTION` parameters, see [BY Option](#by-option).
 - The parameter `INTERVAL` is mainly used to give the length of a period of time. There are two parameter forms:
    - Strings based on the `PromQL Time Durations` format (eg: `3h`, `1h30m`). Visit the [Prometheus documentation](https://prometheus.io/docs/prometheus/latest/querying/basics/#time-durations) for a more detailed description of this format.
-   - `Interval` type. To use the `Interval` type, you need to carry parentheses, (for example: `(INTERVAL '1 year 3 hours 20 minutes')`). Visit [Interval](./functions.md#interval) for a more detailed description of this format.
+   - `Interval` type. To use the `Interval` type, you need to carry parentheses, (for example: `(INTERVAL '1 year 3 hours 20 minutes')`). Visit [Interval](./functions/overview.md#interval) for a more detailed description of this format.
 - `AGGR_FUNCTION(column1, column2,..) RANGE INTERVAL [FILL FILL_OPTION]` is called a Range expression.
    - `AGGR_FUNCTION(column1, column2,..)` is an aggregate function that represents the expression that needs to be aggregated.
    - Keyword `RANGE`, required field, followed by parameter `INTERVAL` specifies the time range of each data aggregation.

docs/nightly/en/user-guide/operations/admin.md

@@ -37,7 +37,7 @@ The `INFORMATION_SCHEMA` database provides access to system metadata, such as th
 
 * [The Storage Location](/user-guide/concepts/storage-location.md).
 * Cluster Failover for GreptimeDB by [Setting Remote WAL](./remote-wal/quick-start.md).
-* [Flush and Compaction for Table & Region](/reference/sql/functions#admin-functions).
+* [Flush and Compaction for Table & Region](/reference/sql/functions/overview#admin-functions).
 * Partition the table by regions, read the [Table Sharding](/contributor-guide/frontend/table-sharding.md) reference.
   * [Migrate the Region](./region-migration.md) for Load Balance.
 * [Expire Data by Setting TTL](/user-guide/concepts/features-that-you-concern#can-i-set-ttl-or-retention-policy-for-different-tables-or-measurements).

docs/nightly/en/user-guide/query-data/sql.md

@@ -85,7 +85,7 @@ select to_unixtime('2024-01-02 00:00:00');
 select to_unixtime('2024-01-02 00:00:00+08:00');
 ```
 
-Please refer to [SELECT](/reference/sql/select.md) and [Functions](/reference/sql/functions.md) for more information.
+Please refer to [SELECT](/reference/sql/select.md) and [Functions](/reference/sql/functions/overview.md) for more information.
 
 ## Limit the number of rows returned
 
@@ -165,7 +165,7 @@ For example, use the `now()` function and the `INTERVAL` keyword to retrieve dat
 SELECT * FROM monitor WHERE ts >= now() - INTERVAL '5 minutes';
 ```
 
-For date and time functions, please refer to [Functions](/reference/sql/functions.md) for more information.
+For date and time functions, please refer to [Functions](/reference/sql/functions/overview.md) for more information.
 
 ### Time zone
 

docs/nightly/zh/faq-and-others/faq.md

@@ -145,7 +145,7 @@ Of course, please use the `compact_table` function:
 select compact_table("test");
 ```
 
-There are many [administration functions](/reference/sql/functions#admin-functions) for database management.
+There are many [administration functions](/reference/sql/functions/overview#admin-functions) for database management.
 
 ### Can GreptimeDB be used to store logs?
 

docs/nightly/zh/reference/sql/functions/overview.md

@@ -245,7 +245,7 @@ select database();
 GreptimeDB 提供一些管理数据库和数据的函数：
 
 * `flush_table(table_name)` 通过表名将表的内存表刷写到 SST 文件。
-* `flush_region(region_id)` 通过 Region Id 将 Region 的内存表刷写到 SST 文件。可以通过 [PARTITIONS](./information-schema/partitions.md) 表查找一张表的所有 Region Id。
+* `flush_region(region_id)` 通过 Region Id 将 Region 的内存表刷写到 SST 文件。可以通过 [PARTITIONS](../information-schema/partitions.md) 表查找一张表的所有 Region Id。
 * `compact_table(table_name)` 通过表名为表发起compaction 任务。
 * `compact_region(region_id)` 通过 Region Id 为 Region 发起 compaction 任务。
 * `migrate_region(region_id, from_peer, to_peer, [timeout])` 在 Datanode 之间迁移 Region，请阅读 [ Region迁移](/user-guide/operations/region-migration)。

docs/nightly/zh/reference/sql/group_by.md

@@ -65,4 +65,4 @@ FROM system_metrics
 GROUP BY dt
 ```
 
-请参考 [date_trunc](./functions.md#date_trunc) 获取更多信息。
+请参考 [date_trunc](./functions/overview.md#date_trunc) 获取更多信息。

docs/nightly/zh/reference/sql/overview.md

@@ -11,7 +11,7 @@
 * [GROUP BY](./group_by.md)
 * [LIMIT](./limit.md)
 * [JOIN](./join.md)
-* [Functions](./functions.md)
+* [Functions](./functions/overview.md)
 * [DELETE](./delete.md)
 * [SHOW](./show.md)
 * [TQL](./tql.md)

docs/nightly/zh/reference/sql/range.md

@@ -25,7 +25,7 @@ INTERVAL :=  TIME_INTERVAL | ( INTERVAL expr )
   - 子关键字 `BY` ，可选字段，后接参数 `(columna, columnb,..)` ，描述了聚合键。详情请见[BY OPTION](#by-option)。
 - 参数 `INTERVAL` ，主要用于给出一段时间长度，有两种参数形式：
   - 基于 `PromQL Time Durations` 格式的字符串（例如：`3h`、`1h30m`）。访问 [Prometheus 文档](https://prometheus.io/docs/prometheus/latest/querying/basics/#time-durations) 获取该格式更详细的说明。
-  - `Interval` 类型，使用 `Interval` 类型需要携带括号,（例如：`(INTERVAL '1 year 3 hours 20 minutes')`）。访问 [Interval](./functions.md#interval) 获取该格式更详细的说明。
+  - `Interval` 类型，使用 `Interval` 类型需要携带括号,（例如：`(INTERVAL '1 year 3 hours 20 minutes')`）。访问 [Interval](./functions/overview.md#interval) 获取该格式更详细的说明。
 - `AGGR_FUNCTION(column1, column2,..) RANGE INTERVAL [FILL FILL_OPTION]` 称为一个 Range 表达式。
   - `AGGR_FUNCTION(column1, column2,..)` 是一个聚合函数，代表需要聚合的表达式。
   - 关键字 `RANGE`，必选字段，后接参数 `INTERVAL` 指定了每次数据聚合的时间范围，

docs/nightly/zh/summary-i18n.yml

@@ -24,6 +24,7 @@ Migrate-to-GreptimeDB: 迁移到 GreptimeDB
 Migrate-to-GreptimeCloud: 迁移到 GreptimeCloud
 Integrations: 集成
 Usage-&-Billing: 用量及费用
+Functions: 函数
 Frontend: Frontend
 Datanode: Datanode
 Flownode: Flownode

docs/nightly/zh/user-guide/operations/admin.md

@@ -37,7 +37,7 @@ ORDER BY datanode_id ASC
 
 * [存储位置说明](/user-guide/concepts/storage-location.md)。
 * 通过 [设置Remote WAL](./remote-wal/quick-start.md) 实现 GreptimeDB 的集群容灾。
-* [Table 和 Region 的 Flush 和 Compaction](/reference/sql/functions#admin-functions)。
+* [Table 和 Region 的 Flush 和 Compaction](/reference/sql/functions/overview#admin-functions)。
 * 通过 Region 对表进行分区，请阅读 [表的分片](/contributor-guide/frontend/table-sharding.md) 参考。
   * [迁移 Region](./region-migration.md) 以实现负载均衡。
 * [通过设置 TTL 过期数据](/user-guide/concepts/features-that-you-concern#can-i-set-ttl-or-retention-policy-for-different-tables-or-measurements)。

docs/nightly/zh/user-guide/query-data/sql.md

@@ -81,7 +81,7 @@ select to_unixtime('2024-01-02 00:00:00');
 select to_unixtime('2024-01-02 00:00:00+08:00');
 ```
 
-请参考 [SELECT](/reference/sql/select.md) 和 [Functions](/reference/sql/functions.md) 获取更多信息。
+请参考 [SELECT](/reference/sql/select.md) 和 [Functions](/reference/sql/functions/overview.md) 获取更多信息。
 
 ## 限制返回的行数
 
@@ -155,7 +155,7 @@ SELECT * FROM monitor WHERE ts > '2022-07-25 10:32:16.408';
 SELECT * FROM monitor WHERE ts >= now() - INTERVAL '5 minutes';
 ```
 
-请参考 [Functions](/reference/sql/functions.md) 获取更多时间函数信息。
+请参考 [Functions](/reference/sql/functions/overview.md) 获取更多时间函数信息。
 
 ### 时区