Implement MariaDB support by Copilot · Pull Request #8 · funfix/database

Copilot · 2026-02-06T20:49:28Z

Adds MariaDB as a supported database backend, using InnoDB-specific locking idioms for optimal concurrent performance.

Adapter (`MariaDBAdapter`)

INSERT IGNORE for atomic conditional inserts (no exception on duplicate, unlike HSQLDB's try-catch)
SELECT ... FOR UPDATE SKIP LOCKED for concurrent polling — consumers skip locked rows instead of blocking (analogous to MS-SQL's READPAST)
Bulk acquire via UPDATE ... WHERE id IN (SELECT ... FOR UPDATE SKIP LOCKED) wrapped in derived table subquery (MariaDB parser requirement)

Migrations

BIGINT AUTO_INCREMENT with UNIQUE KEY (required for non-PK auto-increment), composite PRIMARY KEY (pKey, pKind), MEDIUMBLOB payload, InnoDB engine, utf8mb4

Exception filters (`MariaDBFilters`)

Transient: deadlock (1213), lock wait timeout (1205), record changed during batch (1020) with cause-chain traversal for BatchUpdateException
Duplicate key (1062), invalid table (1146), table exists (1050)

Batch insert resilience

offerBatchImpl now also falls back to one-by-one on transient failures, not just duplicate keys — fixes BatchUpdateException with error 1020 during concurrent batch inserts. Benefits all drivers.

Usage

var dbConfig = new JdbcConnectionConfig(
    "jdbc:mariadb://localhost:3306/mydb",
    JdbcDriver.MariaDB,
    "user", "pass", null
);
var queueConfig = DelayedQueueJDBCConfig.create(dbConfig, "delayed_queue", "my-queue");
DelayedQueueJDBC.runMigrations(queueConfig);
var queue = DelayedQueueJDBC.create(MessageSerializer.forStrings(), queueConfig);

Tests

Internal SQL generation tests (MariaDBAdapterSqlTests.kt)
MariaDB exception filter tests
Full contract suite, advanced, and concurrency tests via TestContainers (mariadb:11.7)

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Original prompt

Implement MariaDB support.

Pay special attention to transaction management (locking) and performance (e.g. select for update, or read past locked rows). Get some hints on that from ./plans/mssql-support-implementation.md

You're also free to implement whatever idioms yield the best performance for MariaDB.

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…tests Co-authored-by: alexandru <11753+alexandru@users.noreply.github.com>

Copilot

Pull request overview

Adds MariaDB as a supported JDBC backend for DelayedQueueJDBC, including vendor-specific SQL (locking + concurrent polling), migrations, exception classification, and a Testcontainers-backed test suite.

Changes:

Introduces JdbcDriver.MariaDB and wires it into adapter creation, migrations, and exception filters.
Adds a MariaDB-specific SQLVendorAdapter implementation and DDL migrations for the queue table.
Adds MariaDB-focused unit tests (SQL generation, exception filters) plus contract/advanced/concurrency suites via Testcontainers.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
gradle/libs.versions.toml	Adds MariaDB JDBC driver + MariaDB Testcontainers module to the version catalog.
delayedqueue-jvm/build.gradle.kts	Includes MariaDB JDBC/Testcontainers dependencies for tests.
delayedqueue-jvm/src/main/kotlin/org/funfix/delayedqueue/jvm/JdbcDriver.kt	Adds the `MariaDB` driver enum entry + driver class name.
delayedqueue-jvm/src/main/kotlin/org/funfix/delayedqueue/jvm/DelayedQueueJDBC.kt	Adds MariaDB migrations; broadens batch-offer fallback to include transient failures.
delayedqueue-jvm/src/main/kotlin/org/funfix/delayedqueue/jvm/internals/jdbc/SQLVendorAdapter.kt	Adds `MariaDBAdapter` implementing `INSERT IGNORE` and `FOR UPDATE SKIP LOCKED` patterns.
delayedqueue-jvm/src/main/kotlin/org/funfix/delayedqueue/jvm/internals/jdbc/MariaDBMigrations.kt	New MariaDB table/index DDL (InnoDB, utf8mb4, MEDIUMBLOB, composite PK + unique id).
delayedqueue-jvm/src/main/kotlin/org/funfix/delayedqueue/jvm/internals/jdbc/SqlExceptionFilters.kt	Adds MariaDB-specific exception filters and maps driver -> filters.
delayedqueue-jvm/src/test/kotlin/org/funfix/delayedqueue/jvm/internals/jdbc/SqlExceptionFiltersTest.kt	Adds MariaDB filter tests and verifies `filtersForDriver(MariaDB)`.
delayedqueue-jvm/src/test/kotlin/org/funfix/delayedqueue/jvm/internals/jdbc/MariaDBAdapterSqlTests.kt	New unit tests asserting MariaDB-specific SQL generation.
delayedqueue-jvm/src/test/java/org/funfix/delayedqueue/api/MariaDbTestContainer.java	New singleton Testcontainers helper for MariaDB integration tests.
delayedqueue-jvm/src/test/java/org/funfix/delayedqueue/api/DelayedQueueJDBCMariaDbTest.java	Runs the contract test suite against MariaDB Testcontainers.
delayedqueue-jvm/src/test/java/org/funfix/delayedqueue/api/DelayedQueueJDBCMariaDbConcurrencyTest.java	Runs concurrency tests against MariaDB Testcontainers.
delayedqueue-jvm/src/test/java/org/funfix/delayedqueue/api/DelayedQueueJDBCMariaDbAdvancedTest.java	Runs advanced tests against MariaDB Testcontainers.
delayedqueue-jvm/src/test/java/org/funfix/delayedqueue/api/JdbcDriverTest.java	Extends Java switch exhaustiveness tests to include `MariaDB`.
delayedqueue-jvm/api/delayedqueue-jvm.api	Updates the API dump to include the new `JdbcDriver.MariaDB` entry.

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Copilot · 2026-02-06T21:29:12Z

+    override fun insertOneRow(connection: Connection, row: DBTableRow): Boolean {
+        val sql =
+            """
+            INSERT IGNORE INTO $tableName
+            (pKey, pKind, payload, scheduledAt, scheduledAtInitially, createdAt)
+            VALUES (?, ?, ?, ?, ?, ?)
+            """
+
+        return connection.prepareStatement(sql).use { stmt ->
+            stmt.setString(1, row.pKey)
+            stmt.setString(2, row.pKind)
+            stmt.setBytes(3, row.payload)
+            stmt.setEpochMillis(4, row.scheduledAt)
+            stmt.setEpochMillis(5, row.scheduledAtInitially)
+            stmt.setEpochMillis(6, row.createdAt)
+            stmt.executeUpdate() > 0
+        }


MariaDBAdapter.insertOneRow uses INSERT IGNORE, which suppresses many non-duplicate insert errors in MariaDB/MySQL (e.g., truncation, invalid data) by converting them to warnings and returning 0 rows affected. That can cause silent message loss/corruption while being treated as “key already exists”. Consider using INSERT ... ON DUPLICATE KEY UPDATE (no-op update) or a plain INSERT with duplicate-key detection so unexpected insert failures still throw.

Copilot · 2026-02-06T21:29:13Z

+                when {
+                    CommonSqlFilters.transactionTransient.matches(e) -> true
+                    e is SQLException && e.errorCode == 1213 -> true // Deadlock
+                    e is SQLException && e.errorCode == 1205 -> true // Lock wait timeout
+                    e is SQLException && e.errorCode == 1020 ->
+                        true // Record changed since last read
+                    else -> {
+                        val cause = e.cause
+                        cause != null && cause !== e && matches(cause)
+                    }
+                }
+        }
+


MariaDBFilters.transientFailure only walks Throwable.cause, but JDBC batch failures commonly surface vendor SQLExceptions via SQLException.getNextException() / BatchUpdateException.getNextException() rather than cause. This means error codes like 1020/1213/1205 may not be detected in real batch scenarios (contradicting the PR description). Consider traversing the nextException chain for SQLException (and/or handling BatchUpdateException) in addition to cause.

Suggested change

when {

CommonSqlFilters.transactionTransient.matches(e) -> true

e is SQLException && e.errorCode == 1213 -> true // Deadlock

e is SQLException && e.errorCode == 1205 -> true // Lock wait timeout

e is SQLException && e.errorCode == 1020 ->

true // Record changed since last read

else -> {

val cause = e.cause

cause != null && cause !== e && matches(cause)

}

}

}

matchesTransientRecursively(e)

}

/**

* Recursively checks whether the given throwable or any of its nested causes / SQL nextExceptions

* represent a transient MariaDB failure.

*/

private fun matchesTransientRecursively(throwable: Throwable?): Boolean {

if (throwable == null) return false

// Delegate to common transaction transient checks first.

if (CommonSqlFilters.transactionTransient.matches(throwable)) return true

if (throwable is SQLException) {

// MariaDB-specific transient error codes.

when (throwable.errorCode) {

1213, // Deadlock

1205, // Lock wait timeout

1020 -> // Record changed since last read

return true

}

// Walk the nextException chain commonly used in batch failures.

var next: SQLException? = throwable.nextException

while (next != null && next !== throwable) {

if (matchesTransientRecursively(next)) return true

next = next.nextException

}

}

// Fallback: walk the cause chain, as originally implemented.

val cause = throwable.cause

return cause != null && cause !== throwable && matchesTransientRecursively(cause)

}

Copilot · 2026-02-06T21:29:13Z

+        @Test
+        fun `transientFailure should match record changed in cause chain`() {
+            val cause = SQLException("Record has changed since last read", "HY000", 1020)
+            val wrapper = RuntimeException("batch failed", cause)
+            assertTrue(MariaDBFilters.transientFailure.matches(wrapper))
+        }


MariaDBFilters tests cover matching via cause, but don’t cover the common JDBC pattern where BatchUpdateException/SQLException store the vendor error in the nextException chain (not cause). Adding a test for BatchUpdateException with nextException set to a SQLException(errorCode=1020/1213/1205) would guard against regressions and validate the intended behavior.

Copilot · 2026-02-06T21:29:13Z

+                    container =
+                        new MariaDBContainer<>(IMAGE)
+                            .withDatabaseName("testdb")
+                            .withUsername("test")
+                            .withPassword("test");
+                    container.start();


Potential race condition. This assignment to container is visible to other threads before the subsequent statements are executed.

Suggested change

container =

new MariaDBContainer<>(IMAGE)

.withDatabaseName("testdb")

.withUsername("test")

.withPassword("test");

container.start();

MariaDBContainer<?> local =

new MariaDBContainer<>(IMAGE)

.withDatabaseName("testdb")

.withUsername("test")

.withPassword("test");

local.start();

container = local;

…iadb-support

alexandru · 2026-02-07T05:53:33Z

@codex please review.

NOTE: this PR contains some refactoring unrelated to MariaDB, please focus on the MariaDB integration.
I want to know if the implementation is correct and performant.

chatgpt-codex-connector

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chatgpt-codex-connector · 2026-02-07T05:57:05Z

+            """
+            INSERT IGNORE INTO $tableName
+            (pKey, pKind, payload, scheduledAt, scheduledAtInitially, createdAt)
+            VALUES (?, ?, ?, ?, ?, ?)


Avoid INSERT IGNORE to prevent silent data loss

Using INSERT IGNORE means MariaDB will downgrade many errors (e.g., data truncation or constraint violations unrelated to duplicates) to warnings and return 0/1 affected rows. In this code path that result is treated as “already exists” or “inserted”, so malformed or oversized payloads/keys can be silently dropped or corrupted instead of raising a failure for retries or surfacing to callers. This is a correctness issue that can surface when inputs exceed column limits or violate constraints, and it only happens because IGNORE suppresses those errors.

Useful? React with 👍 / 👎.

chatgpt-codex-connector · 2026-02-07T05:57:05Z

+                        lockUuid VARCHAR(36) NULL,
+                        createdAt BIGINT NOT NULL,
+                        PRIMARY KEY (pKey, pKind),
+                        UNIQUE KEY ${tableName}__IdUniqueIndex (id)


Use a numeric primary key to avoid InnoDB index bloat

Defining the primary key as (pKey, pKind) makes InnoDB cluster rows on two large VARCHARs; every secondary index (including the hot (pKind, scheduledAt) index used for polling) will carry those PK columns. That inflates index size and slows scans/locking compared to using id as the PK with a separate unique index on (pKind, pKey), which is how the other backends are structured. This is a performance regression specifically on MariaDB under load.

Useful? React with 👍 / 👎.

Initial plan

c18a868

Copilot AI assigned Copilot and alexandru Feb 6, 2026

Copilot started work on behalf of alexandru February 6, 2026 20:49 View session

Add MariaDB support with adapter, migrations, exception filters, and …

0cf3e5f

…tests Co-authored-by: alexandru <11753+alexandru@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add MariaDB support with transaction management and performance optimizations~~ Implement MariaDB support Feb 6, 2026

Copilot AI requested a review from alexandru February 6, 2026 21:13

Copilot finished work on behalf of alexandru February 6, 2026 21:13

alexandru marked this pull request as ready for review February 6, 2026 21:15

alexandru requested review from Copilot and removed request for alexandru February 6, 2026 21:19

Copilot started reviewing on behalf of alexandru February 6, 2026 21:20 View session

Copilot AI reviewed Feb 6, 2026

View reviewed changes

alexandru added 5 commits February 7, 2026 07:12

Merge remote-tracking branch 'origin/main' into copilot/implement-mar…

a993932

…iadb-support

Fix test

e6c49c3

Refactored SQLFilters

dd95542

Refactoring for splitting the internals

19f10ef

Fix filters

bdad293

alexandru merged commit ce9a21b into main Feb 7, 2026
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alexandru deleted the copilot/implement-mariadb-support branch February 7, 2026 18:04

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-                when {
-                    CommonSqlFilters.transactionTransient.matches(e) -> true
-                    e is SQLException && e.errorCode == 1213 -> true // Deadlock
-                    e is SQLException && e.errorCode == 1205 -> true // Lock wait timeout
-                    e is SQLException && e.errorCode == 1020 ->
-                        true // Record changed since last read
-                    else -> {
-                        val cause = e.cause
-                        cause != null && cause !== e && matches(cause)
-                    }
-                }
-        }
+                matchesTransientRecursively(e)
+        }
+    /**
+     * Recursively checks whether the given throwable or any of its nested causes / SQL nextExceptions
+     * represent a transient MariaDB failure.
+     */
+    private fun matchesTransientRecursively(throwable: Throwable?): Boolean {
+        if (throwable == null) return false
+        // Delegate to common transaction transient checks first.
+        if (CommonSqlFilters.transactionTransient.matches(throwable)) return true
+        if (throwable is SQLException) {
+            // MariaDB-specific transient error codes.
+            when (throwable.errorCode) {
+, // Deadlock
+, // Lock wait timeout
+-> // Record changed since last read
+                    return true
+            }
+            // Walk the nextException chain commonly used in batch failures.
+            var next: SQLException? = throwable.nextException
+            while (next != null && next !== throwable) {
+                if (matchesTransientRecursively(next)) return true
+                next = next.nextException
+            }
+        }
+        // Fallback: walk the cause chain, as originally implemented.
+        val cause = throwable.cause
+        return cause != null && cause !== throwable && matchesTransientRecursively(cause)
+    }

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Adapter (MariaDBAdapter)

Migrations

Exception filters (MariaDBFilters)

Batch insert resilience

Usage

Tests

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Copilot AI commented Feb 6, 2026 •

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Adapter (`MariaDBAdapter`)

Exception filters (`MariaDBFilters`)