Add songkant-aws as maintainer

[qianheng-aws]

Description

Welcoming new maintainer SongKan Tang (@songkant-aws ).

Songkan has been a consistent and impactful contributor to the project, with 33 merged PRs to date (and additional work in flight), 15 issues filed (feature proposals, RFCs, and bug reports) and 24+ PRs commented on (beyond his own). https://github.com/opensearch-project/sql/pulls?q=is%3Apr+author%3Asongkant-aws+

Here is a summary of his key contributions:

1. Calcite Engine Migration & Command Support
   Songkan has supported multiple PPL commands in the new engine:
   Patterns command with SIMPLE_PATTERN and BRAIN algorithm methods (Revert stream pattern method in V2 and implement SIMPLE_PATTERN in Calcite #3553, Calcite patterns command brain pattern method #3570)
   Grok command (Support Grok command in Calcite engine #3678)
   Trendline command (Support trendline command in Calcite #3741)
   Append command (Implement Append command with Calcite #4123)
   Group by span over time-based columns with Span UDF (Support group by span over time based column with Span UDF #3421)

2. Query Pushdown Optimization
   Songkan has made significant contributions to query performance related to pushdown:
   Relevance query function pushdown in Calcite (Support relevance query functions pushdown implementation in Calcite #3834)
   Filter script pushdown with RelJson serialization (Filter script pushdown with RelJson serialization in Calcite #3859)
   LIKE function to wildcard query conversion for filter pushdown (Convert like function call to wildcard query for Calcite filter pushdown #3915)
   Sort pushdown for simple and complex expressions (Support pushdown sort by simple expressions #4071, Pushdown sort by complex expressions to scan #4750)
   Sort expression pushdown for SortMergeJoin (Support sort expression pushdown for SortMergeJoin #4830)
   Optimized pushdown script size by including only necessary fields per expression (Optimize pushdown script size with necessary fields per expression #4615)
   General UDAF pushdown as scripts (in progress, General UDAF pushdown as scripts #5064)

3. Patterns Command Enhancement
   Songkan authored the RFC to improve the patterns command with more advanced log pattern algorithms ([RFC] Improve patterns command with more advanced log pattern algorithms #3251) and led the end-to-end implementation:
   Introduced improved pattern algorithm (Improved patterns command with new algorithm #3263)
   Added sample_logs output field for better observability ([Feature][Enhancement] Enhance patterns command with additional sample_logs output field #4155)
   Fixed numbered token handling and made it optional (Fix numbered token bug and make it optional output in patterns command #4402)

4. Bug Fixes & Reliability
   Songkan has consistently addressed bugs across the codebase, demonstrating deep understanding of the query engine internals:
   Fixed relevance query function over-optimization in ReduceExpressionsRule ([BugFix] Fix relevance query function over optimization issue in ReduceExpressionsRule #3851)
   Fixed parse-related functions NULL input handling (Fix parse related functions return behavior in case of NULL input #4381)
   Fixed makeNullLiteral for UDT fields in append/multisearch (Fix the bug of explicit makeNullLiteral for UDT fields #4475)
   Fixed boolean comparison condition simplification bug ([BugFix] Fix the bug when boolean comparison condition is simplifed to field #5071)
   Fixed PushDownContext shallow copy bug ([BugFix] Fix PushDownContext shallow copy bug #5199, in progress)
   Fixed LogPatternAggFunction parameter and return result logic (Fix wrong parameter and return result logic for LogPatternAggFunction #4868)

Changes

Added Songkan Tang | songkant-aws | Amazon to MAINTAINERS.md
Added @songkant-aws to .github/CODEOWNERS

[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

🧪 No relevant tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ No major issues detected

[yuancu]

Welcome, @songkant-aws !

[LantaoJin]

Do not merge this until @peterzhuamazon 's confirming.