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new 2583846a6340 [docs] Clarify hot partition window in SSD/HDD examples
(#4621)
2583846a6340 is described below
commit 2583846a634083be8b6329104f3f2890a25fec0f
Author: Mingyu Chen (Rayner) <[email protected]>
AuthorDate: Fri Nov 13 08:03:20 2026 +0800
[docs] Clarify hot partition window in SSD/HDD examples (#4621)
The SSD/HDD example in #2502 uses the correct reference date,
2021-05-20, but describes `hot_partition_num` as keeping only the most
recent N partitions on SSD. The scheduler also places all future
partitions on SSD, which explains why the example has five SSD
partitions with `hot_partition_num = 2`.
Clarify the hot-partition window and cooldown calculation in English and
Chinese for dev, 4.x, and 3.x. Keep the existing dates and partition
results, explain the historical-partition prerequisite, and state the
example date beside the summarized `SHOW PARTITIONS` output.
Fixes #2502
Validation:
- Checked `DynamicPartitionScheduler.setStorageMediumProperty` on Doris
master, branch-3.0, branch-3.1, branch-4.0, and branch-4.1. Each uses
`offset + hotPartitionNum <= 0` for HDD and `offset + hotPartitionNum`
for SSD cooldown boundaries. [3.1
source](https://github.com/apache/doris/blob/a3e9f66a1106a4208e6855ffef9e0fb8b3c981ff/fe/fe-core/src/main/java/org/apache/doris/clone/DynamicPartitionScheduler.java#L458),
[4.1
source](https://github.com/apache/doris/blob/df8ed67a8e5dbdc91f1065b50dae23d834117800/fe/fe-core/src/main/java/org/apache/doris/clone/DynamicPartitionScheduler.java#L488).
- Independently calculated the seven partitions and cooldown boundaries
for 2021-05-20, verified all 14 partition entries in each of the six
pages, and confirmed headings and links are unchanged.
- `git diff --check` and the changed-file locale synchronization check
pass.
- The changed-file link check reports four existing Chinese
FAQ/troubleshooting anchor errors. The links and headings are unchanged
here; their fixes are already covered by #4430.
- No cluster execution or website build was run for these prose changes.
Review:
- Goal: the text now explains the date and SSD/HDD distribution using
the scheduler's actual rule.
- Scope: six existing pages, limited to this parameter and its examples.
- Information architecture: all active English/Chinese counterparts
updated; archived snapshots unchanged.
- Routing and navigation: no paths, titles, heading anchors, sidebar
items, or redirects changed.
- Frontend and build conventions: no UI, configuration, or build
changes.
- Validation: source comparison, partition arithmetic, locale
synchronization, and whitespace checks completed; existing link-check
findings documented above.
- Other correctness/usability concerns: no additional findings
introduced by the change.
Co-authored-by: morningman <[email protected]>
---
docs/table-design/tiered-storage/tiered-ssd-hdd.md | 14 +++++++++-----
.../current/table-design/tiered-storage/tiered-ssd-hdd.md | 14 +++++++++-----
.../table-design/tiered-storage/tiered-ssd-hdd.md | 8 ++++++--
.../table-design/tiered-storage/tiered-ssd-hdd.md | 14 +++++++++-----
.../table-design/tiered-storage/tiered-ssd-hdd.md | 8 ++++++--
.../table-design/tiered-storage/tiered-ssd-hdd.md | 14 +++++++++-----
6 files changed, 48 insertions(+), 24 deletions(-)
diff --git a/docs/table-design/tiered-storage/tiered-ssd-hdd.md
b/docs/table-design/tiered-storage/tiered-ssd-hdd.md
index 6ea82fdc2956..0a4c0383276a 100644
--- a/docs/table-design/tiered-storage/tiered-ssd-hdd.md
+++ b/docs/table-design/tiered-storage/tiered-ssd-hdd.md
@@ -55,7 +55,7 @@ Tiered storage is implemented based on dynamic partitions.
Doris automatically c
The execution flow of tiered storage is as follows:
1. Enable dynamic partitions when creating the table, and set
`dynamic_partition.storage_medium = HDD`.
-2. Use `dynamic_partition.hot_partition_num` to designate the most recent N
partitions as hot partitions, stored on SSD.
+2. Use `dynamic_partition.hot_partition_num` to keep the current partition,
partitions for the previous `N - 1` time intervals, and all future partitions
on SSD.
3. The system sets a `storage_cooldown_time` for each hot partition.
4. Once the cooldown time is reached, partition data is automatically migrated
from SSD to HDD.
@@ -69,12 +69,12 @@ Tiered storage relies on the following two dynamic
partition parameters:
| Parameter | Purpose
| Default | Notes
|
| -------------------------------------- |
------------------------------------------------------------------------ |
------- | ---------------------------------------------------------------- |
-| `dynamic_partition.hot_partition_num` | Specifies how many of the most
recent partitions are hot, stored on SSD | None | Must be used together
with `storage_medium = HDD` |
+| `dynamic_partition.hot_partition_num` | Keeps the current partition,
partitions for the previous `N - 1` time intervals, and all future partitions
on SSD when `N > 0` | None | Must be used together with `storage_medium =
HDD` |
| `dynamic_partition.storage_medium` | Specifies the final storage medium
for dynamic partitions | HDD | When set to SSD,
`hot_partition_num` no longer takes effect |
### dynamic_partition.hot_partition_num
-- **Function**: Specifies the most recent N partitions as hot partitions.
These partitions are stored on SSD, while the remaining partitions are stored
on HDD.
+- **Function**: For a positive value `N`, keeps the current partition,
partitions for the previous `N - 1` time intervals, and all future partitions
on SSD. Older partitions use HDD.
- **Conditions for use**:
- You must also set `dynamic_partition.storage_medium = HDD`. Otherwise
this parameter does not take effect.
- An SSD device must exist under the storage path. Otherwise partition
creation fails.
@@ -101,6 +101,10 @@ p20210522: ["2021-05-22", "2021-05-23") storage_medium=SSD
storage_cooldown_time
p20210523: ["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_time=2021-05-25 00:00:00
```
+For daily partitions, the current day has offset `0`. With `hot_partition_num
= N > 0` and final storage medium `HDD`, partitions whose offset is greater
than `-N` use SSD. This includes the current day, the previous `N - 1` days,
and all future partitions created by `dynamic_partition.end`. An SSD partition
at offset `i` has a cooldown time at the start of day `i + N` relative to the
current day.
+
+In this example, offsets `-3` and `-2` use HDD; offsets `-1` through `3` use
SSD. On **2021-05-20**, five partitions use SSD even though `hot_partition_num
= 2`. Creating the historical partitions also requires
`dynamic_partition.create_history_partition = true`, as in the complete table
definition below.
+
### dynamic_partition.storage_medium
- **Function**: Specifies the final storage medium for dynamic partitions.
Valid values are `HDD` (default) or `SSD`.
@@ -117,7 +121,7 @@ The following steps show how to create a table that
supports tiered storage and
### Step 1: Create a Tiered Storage Table
-Goal: Create a table with SSD/HDD tiered storage enabled, where the most
recent 2 partitions use SSD and the rest use HDD.
+Goal: Create a table with SSD/HDD tiered storage enabled. With
`hot_partition_num = 2`, the current day, the previous day, and all future
partitions use SSD. Older partitions use HDD.
```sql
CREATE TABLE tiered_table (k DATE)
@@ -145,7 +149,7 @@ Goal: Confirm that partitions are assigned to SSD and HDD
as expected.
SHOW PARTITIONS FROM tiered_table;
```
-Expected output: 7 partitions in total, of which 5 use SSD and 2 use HDD.
+Assuming the table is created on **2021-05-20**, the relevant partition
properties are summarized below: 7 partitions in total, of which 5 use SSD and
2 use HDD.
```Plain
p20210517: ["2021-05-17", "2021-05-18") storage_medium=HDD
storage_cooldown_time=9999-12-31 23:59:59
diff --git
a/i18n/zh-CN/docusaurus-plugin-content-docs/current/table-design/tiered-storage/tiered-ssd-hdd.md
b/i18n/zh-CN/docusaurus-plugin-content-docs/current/table-design/tiered-storage/tiered-ssd-hdd.md
index 7a159a4e0884..84797a69eafe 100644
---
a/i18n/zh-CN/docusaurus-plugin-content-docs/current/table-design/tiered-storage/tiered-ssd-hdd.md
+++
b/i18n/zh-CN/docusaurus-plugin-content-docs/current/table-design/tiered-storage/tiered-ssd-hdd.md
@@ -55,7 +55,7 @@ Doris 支持在 SSD 与 HDD 之间进行层级存储。通过结合动态分区
层级存储的执行流程如下：
1. 创建表时启用动态分区，并指定 `dynamic_partition.storage_medium = HDD`。
-2. 通过 `dynamic_partition.hot_partition_num` 指定最近 N 个分区为热分区，存放在 SSD 上。
+2. 通过 `dynamic_partition.hot_partition_num` 将当前分区、之前 `N - 1`
个时间单位的分区和所有未来分区保留在 SSD 上。
3. 系统为每个热分区设置 `storage_cooldown_time`（冷却时间）。
4. 冷却时间到达后，分区数据从 SSD 自动迁移至 HDD。
@@ -69,12 +69,12 @@ Doris 支持在 SSD 与 HDD 之间进行层级存储。通过结合动态分区
| 参数 | 作用
| 默认值 | 备注 |
| ------------------------------------ |
---------------------------------------------------------- | ------ |
------------------------------------------ |
-| `dynamic_partition.hot_partition_num` | 指定最近多少个分区为热分区，存储在 SSD 上
| 无 | 必须配合 `storage_medium = HDD` 使用 |
+| `dynamic_partition.hot_partition_num` | 当 `N > 0` 时，将当前分区、之前 `N - 1`
个时间单位的分区和所有未来分区保留在 SSD 上 | 无 | 必须配合 `storage_medium = HDD`
使用 |
| `dynamic_partition.storage_medium` | 指定动态分区的最终存储介质
| HDD | 设为 SSD 时 `hot_partition_num` 不再生效 |
### dynamic_partition.hot_partition_num
-- **功能**：指定最近 N 个分区为热分区，这些分区存储在 SSD 上，其余分区存储在 HDD 上。
+- **功能**：当取值 `N > 0` 时，将当前分区、之前 `N - 1` 个时间单位的分区和所有未来分区保留在 SSD 上，更早的分区使用 HDD。
- **使用条件**：
- 必须同时设置 `dynamic_partition.storage_medium = HDD`，否则该参数不会生效。
- 存储路径下必须存在 SSD 设备，否则分区创建会失败。
@@ -101,6 +101,10 @@ p20210522：["2021-05-22", "2021-05-23") storage_medium=SSD
storage_cooldown_tim
p20210523：["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_time=2021-05-25 00:00:00
```
+对于按天分区的表，当天分区的偏移量为 `0`。当 `hot_partition_num = N > 0` 且最终存储介质为 `HDD` 时，偏移量大于
`-N` 的分区使用 SSD，包括当天、之前 `N - 1` 天，以及 `dynamic_partition.end` 创建的所有未来分区。偏移量为 `i`
的 SSD 分区，其冷却时间为相对当天第 `i + N` 天的起始时刻。
+
+本例中，偏移量 `-3`、`-2` 的分区使用 HDD，偏移量 `-1` 到 `3` 的分区使用 SSD。以 **2021-05-20**
为当前日期，`hot_partition_num = 2` 时有 5 个 SSD 分区。创建历史分区还需设置
`dynamic_partition.create_history_partition = true`，见下方完整建表示例。
+
### dynamic_partition.storage_medium
- **功能**：指定动态分区的最终存储介质，可选 `HDD`（默认）或 `SSD`。
@@ -117,7 +121,7 @@ p20210523：["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_tim
### 步骤一：创建分层存储表
-目的：建表并启用 SSD/HDD 分层存储，最近 2 个分区使用 SSD，其余使用 HDD。
+目的：建表并启用 SSD/HDD 分层存储。`hot_partition_num = 2` 时，当天、前一天和所有未来分区使用 SSD，更早的分区使用
HDD。
```sql
CREATE TABLE tiered_table (k DATE)
@@ -145,7 +149,7 @@ PROPERTIES
SHOW PARTITIONS FROM tiered_table;
```
-预期输出：共 7 个分区，其中 5 个使用 SSD，2 个使用 HDD。
+假设建表时当前日期仍为 **2021-05-20**，以下列出与存储分层相关的预期分区信息：共 7 个分区，其中 5 个使用 SSD，2 个使用 HDD。
```Plain
p20210517：["2021-05-17", "2021-05-18") storage_medium=HDD
storage_cooldown_time=9999-12-31 23:59:59
diff --git
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
index e170d1934351..c4a9fd6a2aae 100644
---
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
+++
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
@@ -23,7 +23,7 @@ Doris 支持在不同磁盘类型（SSD 和 HDD）之间进行分层存储，结
### `dynamic_partition.hot_partition_num`
- **功能**：
- - 指定最近的多少个分区为热分区，这些分区存储在 SSD 上，其余分区存储在 HDD 上。
+ - 当取值 `N > 0` 时，将当前分区、之前 `N - 1` 个时间单位的分区和所有未来分区保留在 SSD 上，更早的分区使用 HDD。
- **注意**：
- 必须同时设置 `dynamic_partition.storage_medium = HDD`，否则此参数不会生效。
@@ -50,6 +50,10 @@ dynamic_partition.end = 3
p20210523：["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_time=2021-05-25 00:00:00
```
+对于按天分区的表，当天分区的偏移量为 `0`。当 `hot_partition_num = N > 0` 且最终存储介质为 `HDD` 时，偏移量大于
`-N` 的分区使用 SSD，包括当天、之前 `N - 1` 天，以及 `dynamic_partition.end` 创建的所有未来分区。偏移量为 `i`
的 SSD 分区，其冷却时间为相对当天第 `i + N` 天的起始时刻。
+
+本例中，偏移量 `-3`、`-2` 的分区使用 HDD，偏移量 `-1` 到 `3` 的分区使用 SSD。以 **2021-05-20**
为当前日期，`hot_partition_num = 2` 时有 5 个 SSD 分区。创建历史分区还需设置
`dynamic_partition.create_history_partition = true`，见下方完整建表示例。
+
### `dynamic_partition.storage_medium`
- **功能**：
@@ -86,7 +90,7 @@ dynamic_partition.end = 3
SHOW PARTITIONS FROM tiered_table;
```
-可以看见 7 个分区，5 个使用 SSD, 其它的 2 个使用 HDD。
+假设建表时当前日期仍为 **2021-05-20**，以下列出与存储分层相关的预期分区信息：共 7 个分区，其中 5 个使用 SSD，2 个使用 HDD。
```Plain
p20210517：["2021-05-17", "2021-05-18") storage_medium=HDD
storage_cooldown_time=9999-12-31 23:59:59
diff --git
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
index 7a159a4e0884..84797a69eafe 100644
---
a/i18n/zh-CN/docusaurus-plugin-content-docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
+++
b/i18n/zh-CN/docusaurus-plugin-content-docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
@@ -55,7 +55,7 @@ Doris 支持在 SSD 与 HDD 之间进行层级存储。通过结合动态分区
层级存储的执行流程如下：
1. 创建表时启用动态分区，并指定 `dynamic_partition.storage_medium = HDD`。
-2. 通过 `dynamic_partition.hot_partition_num` 指定最近 N 个分区为热分区，存放在 SSD 上。
+2. 通过 `dynamic_partition.hot_partition_num` 将当前分区、之前 `N - 1`
个时间单位的分区和所有未来分区保留在 SSD 上。
3. 系统为每个热分区设置 `storage_cooldown_time`（冷却时间）。
4. 冷却时间到达后，分区数据从 SSD 自动迁移至 HDD。
@@ -69,12 +69,12 @@ Doris 支持在 SSD 与 HDD 之间进行层级存储。通过结合动态分区
| 参数 | 作用
| 默认值 | 备注 |
| ------------------------------------ |
---------------------------------------------------------- | ------ |
------------------------------------------ |
-| `dynamic_partition.hot_partition_num` | 指定最近多少个分区为热分区，存储在 SSD 上
| 无 | 必须配合 `storage_medium = HDD` 使用 |
+| `dynamic_partition.hot_partition_num` | 当 `N > 0` 时，将当前分区、之前 `N - 1`
个时间单位的分区和所有未来分区保留在 SSD 上 | 无 | 必须配合 `storage_medium = HDD`
使用 |
| `dynamic_partition.storage_medium` | 指定动态分区的最终存储介质
| HDD | 设为 SSD 时 `hot_partition_num` 不再生效 |
### dynamic_partition.hot_partition_num
-- **功能**：指定最近 N 个分区为热分区，这些分区存储在 SSD 上，其余分区存储在 HDD 上。
+- **功能**：当取值 `N > 0` 时，将当前分区、之前 `N - 1` 个时间单位的分区和所有未来分区保留在 SSD 上，更早的分区使用 HDD。
- **使用条件**：
- 必须同时设置 `dynamic_partition.storage_medium = HDD`，否则该参数不会生效。
- 存储路径下必须存在 SSD 设备，否则分区创建会失败。
@@ -101,6 +101,10 @@ p20210522：["2021-05-22", "2021-05-23") storage_medium=SSD
storage_cooldown_tim
p20210523：["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_time=2021-05-25 00:00:00
```
+对于按天分区的表，当天分区的偏移量为 `0`。当 `hot_partition_num = N > 0` 且最终存储介质为 `HDD` 时，偏移量大于
`-N` 的分区使用 SSD，包括当天、之前 `N - 1` 天，以及 `dynamic_partition.end` 创建的所有未来分区。偏移量为 `i`
的 SSD 分区，其冷却时间为相对当天第 `i + N` 天的起始时刻。
+
+本例中，偏移量 `-3`、`-2` 的分区使用 HDD，偏移量 `-1` 到 `3` 的分区使用 SSD。以 **2021-05-20**
为当前日期，`hot_partition_num = 2` 时有 5 个 SSD 分区。创建历史分区还需设置
`dynamic_partition.create_history_partition = true`，见下方完整建表示例。
+
### dynamic_partition.storage_medium
- **功能**：指定动态分区的最终存储介质，可选 `HDD`（默认）或 `SSD`。
@@ -117,7 +121,7 @@ p20210523：["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_tim
### 步骤一：创建分层存储表
-目的：建表并启用 SSD/HDD 分层存储，最近 2 个分区使用 SSD，其余使用 HDD。
+目的：建表并启用 SSD/HDD 分层存储。`hot_partition_num = 2` 时，当天、前一天和所有未来分区使用 SSD，更早的分区使用
HDD。
```sql
CREATE TABLE tiered_table (k DATE)
@@ -145,7 +149,7 @@ PROPERTIES
SHOW PARTITIONS FROM tiered_table;
```
-预期输出：共 7 个分区，其中 5 个使用 SSD，2 个使用 HDD。
+假设建表时当前日期仍为 **2021-05-20**，以下列出与存储分层相关的预期分区信息：共 7 个分区，其中 5 个使用 SSD，2 个使用 HDD。
```Plain
p20210517：["2021-05-17", "2021-05-18") storage_medium=HDD
storage_cooldown_time=9999-12-31 23:59:59
diff --git
a/versioned_docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
b/versioned_docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
index 112bc83b96ea..c139af8b522c 100644
--- a/versioned_docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
+++ b/versioned_docs/version-3.x/table-design/tiered-storage/tiered-ssd-hdd.md
@@ -22,7 +22,7 @@ For more information on dynamic partitioning, please refer
to: [Data Partitionin
### `dynamic_partition.hot_partition_num`
- **Function**:
- - Specifies how many of the most recent partitions are hot partitions, which
are stored on SSD, while the remaining partitions are stored on HDD.
+ - For a positive value `N`, keeps the current partition, partitions for the
previous `N - 1` time intervals, and all future partitions on SSD. Older
partitions use HDD.
- **Note**:
- `"dynamic_partition.storage_medium" = "HDD"` must be set simultaneously;
otherwise, this parameter will not take effect.
@@ -50,6 +50,10 @@ The system will automatically create the following
partitions and configure thei
p20210523：["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_time=2021-05-25 00:00:00
```
+For daily partitions, the current day has offset `0`. With `hot_partition_num
= N > 0` and final storage medium `HDD`, partitions whose offset is greater
than `-N` use SSD. This includes the current day, the previous `N - 1` days,
and all future partitions created by `dynamic_partition.end`. An SSD partition
at offset `i` has a cooldown time at the start of day `i + N` relative to the
current day.
+
+In this example, offsets `-3` and `-2` use HDD; offsets `-1` through `3` use
SSD. On **2021-05-20**, five partitions use SSD even though `hot_partition_num
= 2`. Creating the historical partitions also requires
`dynamic_partition.create_history_partition = true`, as in the complete table
definition below.
+
### `dynamic_partition.storage_medium`
- **Function**:
@@ -86,7 +90,7 @@ The system will automatically create the following partitions
and configure thei
SHOW PARTITIONS FROM tiered_table;
```
-You should have 7 partitions, 5 of which use SSD as the storage medium, while
the other 2 use HDD.
+Assuming the table is created on **2021-05-20**, the relevant partition
properties are summarized below: 7 partitions in total, of which 5 use SSD and
2 use HDD.
```Plain
p20210517：["2021-05-17", "2021-05-18") storage_medium=HDD
storage_cooldown_time=9999-12-31 23:59:59
diff --git
a/versioned_docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
b/versioned_docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
index 6ea82fdc2956..0a4c0383276a 100644
--- a/versioned_docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
+++ b/versioned_docs/version-4.x/table-design/tiered-storage/tiered-ssd-hdd.md
@@ -55,7 +55,7 @@ Tiered storage is implemented based on dynamic partitions.
Doris automatically c
The execution flow of tiered storage is as follows:
1. Enable dynamic partitions when creating the table, and set
`dynamic_partition.storage_medium = HDD`.
-2. Use `dynamic_partition.hot_partition_num` to designate the most recent N
partitions as hot partitions, stored on SSD.
+2. Use `dynamic_partition.hot_partition_num` to keep the current partition,
partitions for the previous `N - 1` time intervals, and all future partitions
on SSD.
3. The system sets a `storage_cooldown_time` for each hot partition.
4. Once the cooldown time is reached, partition data is automatically migrated
from SSD to HDD.
@@ -69,12 +69,12 @@ Tiered storage relies on the following two dynamic
partition parameters:
| Parameter | Purpose
| Default | Notes
|
| -------------------------------------- |
------------------------------------------------------------------------ |
------- | ---------------------------------------------------------------- |
-| `dynamic_partition.hot_partition_num` | Specifies how many of the most
recent partitions are hot, stored on SSD | None | Must be used together
with `storage_medium = HDD` |
+| `dynamic_partition.hot_partition_num` | Keeps the current partition,
partitions for the previous `N - 1` time intervals, and all future partitions
on SSD when `N > 0` | None | Must be used together with `storage_medium =
HDD` |
| `dynamic_partition.storage_medium` | Specifies the final storage medium
for dynamic partitions | HDD | When set to SSD,
`hot_partition_num` no longer takes effect |
### dynamic_partition.hot_partition_num
-- **Function**: Specifies the most recent N partitions as hot partitions.
These partitions are stored on SSD, while the remaining partitions are stored
on HDD.
+- **Function**: For a positive value `N`, keeps the current partition,
partitions for the previous `N - 1` time intervals, and all future partitions
on SSD. Older partitions use HDD.
- **Conditions for use**:
- You must also set `dynamic_partition.storage_medium = HDD`. Otherwise
this parameter does not take effect.
- An SSD device must exist under the storage path. Otherwise partition
creation fails.
@@ -101,6 +101,10 @@ p20210522: ["2021-05-22", "2021-05-23") storage_medium=SSD
storage_cooldown_time
p20210523: ["2021-05-23", "2021-05-24") storage_medium=SSD
storage_cooldown_time=2021-05-25 00:00:00
```
+For daily partitions, the current day has offset `0`. With `hot_partition_num
= N > 0` and final storage medium `HDD`, partitions whose offset is greater
than `-N` use SSD. This includes the current day, the previous `N - 1` days,
and all future partitions created by `dynamic_partition.end`. An SSD partition
at offset `i` has a cooldown time at the start of day `i + N` relative to the
current day.
+
+In this example, offsets `-3` and `-2` use HDD; offsets `-1` through `3` use
SSD. On **2021-05-20**, five partitions use SSD even though `hot_partition_num
= 2`. Creating the historical partitions also requires
`dynamic_partition.create_history_partition = true`, as in the complete table
definition below.
+
### dynamic_partition.storage_medium
- **Function**: Specifies the final storage medium for dynamic partitions.
Valid values are `HDD` (default) or `SSD`.
@@ -117,7 +121,7 @@ The following steps show how to create a table that
supports tiered storage and
### Step 1: Create a Tiered Storage Table
-Goal: Create a table with SSD/HDD tiered storage enabled, where the most
recent 2 partitions use SSD and the rest use HDD.
+Goal: Create a table with SSD/HDD tiered storage enabled. With
`hot_partition_num = 2`, the current day, the previous day, and all future
partitions use SSD. Older partitions use HDD.
```sql
CREATE TABLE tiered_table (k DATE)
@@ -145,7 +149,7 @@ Goal: Confirm that partitions are assigned to SSD and HDD
as expected.
SHOW PARTITIONS FROM tiered_table;
```
-Expected output: 7 partitions in total, of which 5 use SSD and 2 use HDD.
+Assuming the table is created on **2021-05-20**, the relevant partition
properties are summarized below: 7 partitions in total, of which 5 use SSD and
2 use HDD.
```Plain
p20210517: ["2021-05-17", "2021-05-18") storage_medium=HDD
storage_cooldown_time=9999-12-31 23:59:59
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