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Diffstat (limited to 'doc/development/database/clickhouse/gitlab_activity_data.md')
-rw-r--r-- | doc/development/database/clickhouse/gitlab_activity_data.md | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/doc/development/database/clickhouse/gitlab_activity_data.md b/doc/development/database/clickhouse/gitlab_activity_data.md index 6ba11b8afaf..7c30703a016 100644 --- a/doc/development/database/clickhouse/gitlab_activity_data.md +++ b/doc/development/database/clickhouse/gitlab_activity_data.md @@ -246,9 +246,9 @@ ORDER BY id; A few changes compared to the PostgreSQL version: -- `target_type` uses [an optimization](https://clickhouse.com/docs/en/sql-reference/data-types/lowcardinality/) for low-cardinality column values. +- `target_type` uses [an optimization](https://clickhouse.com/docs/en/sql-reference/data-types/lowcardinality) for low-cardinality column values. - `fingerprint` becomes an integer and leverages a performant integer-based hashing function such as xxHash64. -- All columns get a default value, the 0 default value for the integer columns means no value. See the related [best practices](https://clickhouse.com/docs/en/cloud/bestpractices/avoid-nullable-columns/). +- All columns get a default value, the 0 default value for the integer columns means no value. See the related [best practices](https://clickhouse.com/docs/en/cloud/bestpractices/avoid-nullable-columns). - `NOT NULL` to ensure that we always use the default values when data is missing (different behavior compared to PostgreSQL). - The "primary" key automatically becomes the `id` column due to the `ORDER BY` clause. @@ -276,7 +276,7 @@ ClickHouse will eventually "replace" the rows with the same primary key in the b SELECT * FROM events FINAL ``` -Adding `FINAL` to a query can have significant performance consequences, some of the issues are documented in the [ClickHouse documentation](https://clickhouse.com/docs/en/sql-reference/statements/select/from/#final-modifier). +Adding `FINAL` to a query can have significant performance consequences, some of the issues are documented in the [ClickHouse documentation](https://clickhouse.com/docs/en/sql-reference/statements/select/from#final-modifier). We should always expect duplicated values in the table, so we must take care of the deduplication in query time. |