Summary

Together with our global community of contributors, GreptimeDB continues to evolve and flourish as a growing open-source project. We are grateful to each and every one of you.

Below are the highlights among recent commits:

• Introduced CTE in TQL, allowing hybrid usage with SQL CTEs for more flexible queries.
• Added mysql.prepared_stmt_cache_size configuration to control the number of cached prepared statements.
• Aligned the behavior of label_join and label_replace with Prometheus, improving PromQL expression compatibility.
• Implemented last-not-null and last-row deduplicate strategies for the Flat Parquet format.

Contributors

For the past two weeks, our community has been super active with a total of 116 PRs merged. 6 PRs from 3 individual contributors merged successfully and lots pending to be merged.

Congrats on becoming our most active contributors in the past 2 weeks:

• @kemingy docs#2033
• @sunheyi6 db#6639
• @yihong0618 db#6720 db#6718 db#6714 db#6708

👏 Welcome @kemingy to the community as a new contributor with a successfully merged PR, and more PRs from other individual contributors are waiting to be merged.

（Figure 1: New Contributor of GreptimeDB）

👏 A big THANK YOU to all our members and contributors! It is people like you who are making GreptimeDB a great product. Let's build an even greater community together.

Highlights of Recent PRs

db#6639 Added mysql.prepared_stmt_cache_size Configuration

Introduced a new configuration to control the number of cached MySQL prepared statements. The default value is 10000.

db#6645 TQL Support for CTE (Common Table Expression)

Added CTE support for TQL, allowing hybrid usage with SQL CTEs. For example, you can first query data using TQL and then filter it via SQL subqueries for more flexible query combinations.

-- TQL CTE with column aliases
WITH tql (the_timestamp, the_value) as (
    TQL EVAL (0, 40, '10s') metric
)
SELECT * FROM tql;

+---------------------+-----------+
| the_timestamp       | the_value |
+---------------------+-----------+
| 1970-01-01T00:00:00 | 0.0       |
| 1970-01-01T00:00:10 | 8.0       |
| 1970-01-01T00:00:20 | 8.0       |
| 1970-01-01T00:00:30 | 2.0       |
| 1970-01-01T00:00:40 | 3.0       |
+---------------------+-----------+

-- Hybrid CTEs (TQL + SQL)
WITH 
    tql_data (ts, val) AS (TQL EVAL (0, 40, '10s') metric),
    filtered AS (SELECT * FROM tql_data WHERE val > 5)
SELECT count(*) FROM filtered;

+----------+
| count(*) |
+----------+
| 2        |
+----------+

db#6714 db#6720 Improved PromQL Expression Compatibility

Fixed label_join and label_replace behaviors to align with Prometheus, enhancing PromQL expression compatibility.

db#6691 Added SQL Formatting HTTP Endpoint

Introduced the /v1/sql/format endpoint for SQL formatting.

Example:

curl -s "http://localhost:4000/v1/sql/format?sql=select%201%20as%20x"

Output:

{
  "formatted": "SELECT 1 AS x;"
}

db#6741 Optimized Remote WAL Pruning Strategy

Used estimated data size from statistics to prune WAL, ensuring that Datanode startup does not replay excessive data even in worst-case scenarios.

db#6709 db#6695 Deduplication Strategies for Flat Parquet Format

Added support for last-not-null and last-row deduplication strategies.

Good First Issue

Issue#6287 Allows users to specify date and timestamp formats when using COPY TO

Keywords: Timestamp format

Difficulty: Simple

Issue#6286 Supports exporting compressed CSV or JSON files

Keywords: Data export

Difficulty: Simple

Issue #6334 Enhances KILL support for INSERT INTO SELECT queries

Keywords: Query engine

Difficulty: Medium