Welcome to Metabase's Discussion Forum. October 17, 2015. Embedding a Metabase Dashboard. With 0.39 all my Field Filters are without type. ClickHouse can read messages directly from a Kafka topic using the Kafka table engine coupled with a materialized view that fetches messages and pushes them to a ClickHouse target table. In clickhouse-local File engine accepts file path in addition to Format. Default input/output streams can be specified using numeric or human-readable names like 0 or stdin, 1 or stdout. It is possible to read and write compressed files based on an additional engine parameter or file extension (gz, br or xz).
GitHub - oliverzgy/metabase: metabase + clickhouse datasource. 1 branch 0 tags. Use Git or checkout with SVN using the web URL. The Yandex ClickHouse is a fast, column-oriented DBMS for data analysis. This open-source database management system is fully fault-tolerant and linearly scalable. Instead of other NoSQL DBMS, the.
ClickHouse is known as a data analytics processing engine. ClickHouse is one of the open-source column-oriented database-oriented management systems capable of real-time generation of analytical data reports using SQL queries.
Clickhouse came a long way since it inception 3 years ago.
Why Mydbops recommends ClickHouse for Analytics ?
- ClickHouse is a Columnar Store built for SORT / SEARCH queries performance on a very large volume of database.
- In Columnar Database Systems the values from different columns are stored separately, and data from the same column is stored together – Benefits Performance of Analytical Queries (ORDER / GROUP BY & Aggregation SQLs).
- Columnar Stores are best suited for analytics because of their ability to retrieve just those columns instead of reading all of the rows and filter out unneeded data makes the data accessed faster.
- Easy integration with MySQL and other DB engines. ( MySQL and Clickhouse data migration )
Need for Backup and Restore:
- As a DBA responsibility, we have to backup the data regularly for security reasons.
- If the database crashes or some fatal errors happen, backup is the only way to restore the data and to reduce the loss to the minimum.
There are multiple ways of taking backup. but they all have their own shortcomings. We will be discussing about the below two methods and how to perform the backup and restoration with the below two methods.
- Clickhouse Client
- Clickhouse backup tool
Method 1 ( Using ClickHouse Client ):
ClickHouse Client is a simple way to backup the data and restore it in ClickHouse without any additional tooling. We are going to make the backup of metadata and data separately here
In example, I am taking the dump of the structure of the table “test_table” from the database “testing” with the TAbSeparatedRaw format. This format is only appropriate for outputting a query result, but not for parsing (retrieving data to insert in a table). ( i.e ) Rows are written without escaping.
I have created the database named “testing1” and trying to restore metadata backup taken earlier.
Restoring backup :
Metadata Validation :
Here is the same comparison of the table Structure from dump file and restored data :
Data Backup :
Before taking the dump of the data, Let us validate the count of records that are going to backup.We can validate the records by making a count.
Clickhouse Create Database
Here I’m taking the dump of the table “test_table” with TabSeparated format (tsv). In a tab-separated (tsv) format, data is written by row. Each row contains the values separated by tabs. Values are written in text format, without enclosing quotation marks, and with special characters escaped.
Data Restore :
We need to ensure the database and the table (metadata) is created. The table format should be the same as the source table format. The meta data is restored and data dump is restored.
Once the data dump is restored, I have cross checked the count of the data which is restored in the database from the dump file
We can make an automated program to make the metadata and data backup of each table. And the recovery also has to be formulated too.
Method 2 (Clickhouse-backup):
Clickhouse-backup tool for easy backup and restore with S3 (AWS) and GCS support. It is an open source tool which is available on git.
- Supports Full and incremental backups.
- Supports AWS, GCS, and Alibaba cloud object stores.
- Ease of configuration with environment variables.
- Support backup administrative tasks like list, delete, and download.
Run the clickhouse backup tool from root user or clickhouse user
Default Config Path :
Default config path is defined in the location /var/lib/clickhouse/backup/
Metabase Clickhouse Github
We shouldn’t change the file permission for the default path /var/lib/clickhouse/backup/. As this path contains the hard links. If we change the permission or ownership of default path on hard link, this will be changed the clickhouse too. This will leads to data corruption.
Config File :
All options can be overwritten via environment variables
- Backup the data from tool:
From the backup tool, i have used the option “create” to create a new backup.
By default, while creating the backup from this backup tool, It will create the folder metadata and shadow under the backup directory.
In metadata directory, the metadata file will be present. ( i.e ) it contains the table structure.
In the shadow directory, the data files will be present.
The default dump file is stored in the path -> /var/lib/clickhouse/backup/.
[[email protected] testing]# cat test_table.sql
- List the dump file :
We can check the list of backups using the option “list” from the backup tool. It’s shows the dump file with the created date time.
- Restoring the dump file using clickhouse-backup tool :
” Restore ” is an option to restore the data from the dump file in the clickHouse server.
While restoring from clickHouse backup tool, first it will restore the metadata ( Structure of the table ) from the dump file which is in the metadata directory. Once the metadata is restored in the table, it will prepare the data by restoring the data files present in the shadow directory. Finally, it will do an ALTER TABLE…ATTACH PART. Simply it will add the data to the table from the detached directory.
Validating the logs from the restored backup tool :
There is best pros in the backup tool in which it differentiate the metadata structure and data files in the separate folder such as metadata dir and shadow directory under the backup directory. As mentioned earlier, The data structure will be available in meta data directory and data files will be available in the shadow directory under the mentioned backup directory.
There are some cons in the backup tool as the backup size of remote storage is maximum upto 5TB. This backup tool support only MergeTree family table engine
These are the simple possible ways to backup and restore the data from clickHouse server, We can choose the backup type based on our requirement. Depending on the size of the data, we need to choose the backup type based on our environment. ClickHouse-Copier is another way to take the backup. In the upcoming day, we will discuss the more about Clickhosue further.