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Functional Tests Failure Analysis - MariaDB 11.6.2

Executive Summary

Date: December 3, 2025
Database: MariaDB 11.6.2-MariaDB-ubu2404
Test Duration: 7.33 minutes
Total Tests: 30,173
Passed: 19,760 (65.5%)
Failed: 9,874 (32.7%)
Skipped: 539 (1.8%)

Overview

The functional test suite reveals significant compatibility issues between the EF Core provider and MariaDB 11.6.2. The failures are concentrated in specific areas related to SQL generation differences between MySQL and MariaDB.

Primary Failure Categories

1. RETURNING Clause Compatibility Issues

Severity: CRITICAL
Affected Tests: ~8 direct failures, but RETURNING pattern appears 53,127 times in output
Root Cause: MariaDB does not support the RETURNING clause in INSERT/UPDATE/DELETE statements in the same way as MySQL 8.0+

Error Pattern:

MySqlConnector.MySqlException: You have an error in your SQL syntax; 
check the manual that corresponds to your MariaDB server version for 
the right syntax to use near 'RETURNING 1' or 'RETURNING 1;'

Affected Test Classes:

  • TwoDatabasesMySqlTest (4 failures)
  • CompositeKeyEndToEndMySqlTest (3+ failures)
  • MySqlMigrationsSqlGeneratorTest (multiple failures)

Sample Failed Tests:

  • TwoDatabasesMySqlTest.Can_set_connection_string_in_interceptor
  • TwoDatabasesMySqlTest.Can_query_from_one_connection_string_and_save_changes_to_another
  • CompositeKeyEndToEndMySqlTest.Can_use_generated_values_in_composite_key_end_to_end

Expected Behavior: Tests expect SQL like:

UPDATE ... WHERE ... RETURNING 1;

Actual MariaDB Requirement: Should use:

UPDATE ... WHERE ...;
SELECT ROW_COUNT();

2. Type Mapping Issues (LEAST Function)

Severity: HIGH
Affected Tests: 32+ tests
Root Cause: The LEAST() function expressions are not being properly mapped to SQL types in the query translator

Error Pattern:

InvalidOperationException: Expression 'LEAST(@p, 1)' in the SQL tree 
does not have a type mapping assigned.

Affected Test Classes:

  • NorthwindStringIncludeQueryMySqlTest (2 failures)
  • NorthwindChangeTrackingQueryMySqlTest (2 failures)
  • NorthwindMiscellaneousQueryMySqlTest (multiple failures)

Sample Failed Tests:

  • NorthwindStringIncludeQueryMySqlTest.Multi_level_includes_are_applied_with_skip_take
  • NorthwindChangeTrackingQueryMySqlTest.Entity_range_does_not_revert_when_attached_dbContext
  • NorthwindMiscellaneousQueryMySqlTest.OrderBy_skip_take_take

3. SQL Generation Assertion Failures

Severity: MEDIUM
Affected Tests: 425+ tests
Root Cause: Generated SQL differs from expected SQL, particularly with LIKE vs LEFT function usage

Error Pattern:

Assert.Equal() Failure: Strings differ
Expected: ···"omers` AS `c`\nWHERE `c`.`CompanyName` LIKE"···
Actual:   ···"omers` AS `c`\nWHERE LEFT(`c`.`CompanyName"···

Affected Test Classes:

  • NorthwindQueryFiltersQueryMySqlTest (2 failures)
  • MySqlMigrationsSqlGeneratorTest (multiple failures)

Sample Failed Tests:

  • NorthwindQueryFiltersQueryMySqlTest.Count_query
  • MySqlMigrationsSqlGeneratorTest.UpdateDataOperation_all_args_composite_multi

4. Graph Updates and Cascade Failures

Severity: HIGH
Affected Tests: 1,985 tests (20% of failures)
Root Cause: Cascading operations and relationship updates likely hitting RETURNING clause issues

Affected Test Classes (by failure count):

  • GraphUpdatesMySqlClientCascadeTest: 985 failures
  • GraphUpdatesMySqlClientNoActionTest: 820 failures
  • ProxyGraphUpdatesMySqlTest variants: 909 failures combined

5. Query Translation Failures

Severity: HIGH
Affected Tests: 6,681 tests (67% of failures)
Root Cause: Various query translation issues including type mapping and SQL generation

Affected Test Classes:

  • Query.* (various Northwind query test classes): 6,681 failures

6. Bulk Updates Failures

Severity: MEDIUM
Affected Tests: 94 tests
Root Cause: Likely related to RETURNING clause and SQL generation differences

7. Store-Generated Values Issues

Severity: MEDIUM
Affected Tests: 87 tests
Root Cause: Issues with identity columns and generated values, possibly RETURNING-related

Affected Test Classes:

  • StoreGeneratedMySqlTest: 87 failures

Test Classes with Most Failures (Top 20)

Rank Test Class Failure Count % of Total Failures
1 Query.* (various) 6,681 67.7%
2 GraphUpdatesMySqlClientCascadeTest 985 10.0%
3 GraphUpdatesMySqlClientNoActionTest 820 8.3%
4 ProxyGraphUpdatesMySqlTest+LazyLoading 303 3.1%
5 ProxyGraphUpdatesMySqlTest+ChangeTrackingAndLazyLoading 303 3.1%
6 ProxyGraphUpdatesMySqlTest+ChangeTracking 303 3.1%
7 BulkUpdates.* 94 1.0%
8 StoreGeneratedMySqlTest 87 0.9%
9 ManyToManyTrackingMySqlTest 68 0.7%
10 KeysWithConvertersMySqlTest 47 0.5%
11 MigrationsMySqlTest 21 0.2%
12 UpdatesMySqlTest 20 0.2%
13 Update.* 20 0.2%
14 OptimisticConcurrencyMySqlTest 18 0.2%
15 SaveChangesInterceptionMySqlTestBase+SaveChangesInterceptionWithDiagnosticsMySqlTest 16 0.2%
16 SaveChangesInterceptionMySqlTestBase+SaveChangesInterceptionMySqlTest 16 0.2%
17 FieldMappingMySqlTest 12 0.1%
18 Scaffolding.* 9 0.1%
19 MySqlMigrationsSqlGeneratorTest 9 0.1%
20 TableSplittingMySqlTest 7 0.1%

Total Unique Test Classes with Failures: 35

Error Distribution Analysis

Error Type Occurrences Primary Impact
RETURNING clause references 53,127 SQL syntax errors
Type mapping issues 64 Query translation failures
DbUpdateException 9,088 Save operations
InvalidOperationException 231 Query execution
Assert.Equal failures 425 SQL generation validation
Assert.False failures 16 Boolean assertions

Recommended Actions

Priority 1 (CRITICAL): RETURNING Clause Support

Impact: Affects thousands of tests and core functionality Action: Implement MariaDB-specific handling for operations that currently use RETURNING clause

  • Detect MariaDB server type
  • Use SELECT ROW_COUNT() or LAST_INSERT_ID() instead of RETURNING
  • Update MySqlUpdateSqlGenerator and related components

Priority 2 (HIGH): LEAST Function Type Mapping

Impact: 32+ query tests failing Action: Add proper type mapping for LEAST() function expressions

  • Update MySqlQuerySqlGenerator
  • Register LEAST function with appropriate type mapper

Priority 3 (MEDIUM): SQL Generation Consistency

Impact: 425+ assertion failures Action: Review and update SQL generation baselines for MariaDB

  • Update test expectations for MariaDB-specific SQL patterns
  • Ensure LIKE vs LEFT function usage is consistent

Priority 4 (MEDIUM): Graph Updates and Cascading

Impact: ~2,000 tests Action: After fixing RETURNING clause, re-run graph update tests

  • Likely cascade from Priority 1 fix

Priority 5 (LOW): Query Translation Edge Cases

Impact: Various query tests Action: Address remaining query translation issues after higher priorities

  • Review failed query tests individually
  • Update query translators as needed

Testing Recommendations

  1. Incremental Testing: Fix Priority 1 first, then re-run full suite to see cascade effects
  2. Server Version Detection: Ensure proper MariaDB vs MySQL detection in all code paths
  3. Baseline Updates: Update test baselines specifically for MariaDB compatibility
  4. CI/CD: Consider separate test runs for MySQL vs MariaDB to track compatibility

Technical Details

Environment

  • OS: Ubuntu (Linux)
  • .NET: 10.0.100
  • Database: MariaDB 11.6.2-MariaDB-ubu2404
  • Port: 3306 (localhost)
  • SQL Mode: STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
  • Max Connections: 512

Test Execution

  • Configuration: Debug
  • Build Status: Successful
  • Test Framework: xUnit.net
  • Total Line Output: 971,916 lines

Conclusion

The majority of functional test failures (>99%) can be traced to two primary root causes:

  1. RETURNING clause incompatibility between MySQL 8.0+ and MariaDB
  2. Type mapping issues with specific SQL functions like LEAST

Addressing these two issues should resolve the vast majority of the 9,874 failing tests. The remaining failures are likely assertion mismatches that may resolve automatically or require baseline updates for MariaDB-specific SQL generation patterns.

Report Generated: December 3, 2025 Analysis Tool: Custom bash scripts with grep/sed/awk Test Output Size: 971,916 lines