dbflux_driver_mysql

Features

MySQL and MariaDB relational driver implementations in one crate.
Supports SQL execution, schema discovery, indexes, foreign keys, check constraints, and unique constraints.
Supports authentication, SSL, SSH tunneling, and URI/manual connection modes.
Supports query cancellation through a dedicated cancel path (KILL QUERY flow).
Includes SQL/code generation for CRUD, indexes, foreign keys, and table DDL operations.
Routine discovery: lists stored procedures and user-defined functions from information_schema.ROUTINES including parameter types and return type hints (Functions only).
Routine definition: retrieves the full CREATE FUNCTION or CREATE PROCEDURE body via SHOW CREATE FUNCTION/SHOW CREATE PROCEDURE (read-only; definition is not editable or executable in the viewer).
Multi-statement scripts (several ;-separated statements) are split and executed statement by statement, each through the typed prepared path, returning one result set per statement.

Instance Metrics

Exposes a curated set of live server metrics sourced from SHOW GLOBAL STATUS:

mysql.threads_connected — current open connections
mysql.threads_running — currently executing queries
mysql.queries_per_sec — queries per second (cumulative counter)
mysql.innodb_buffer_pool_hit_ratio — InnoDB buffer pool read efficiency
mysql.innodb_rows_read — rows read from InnoDB storage engine
mysql.innodb_rows_inserted — rows inserted into InnoDB
mysql.innodb_rows_updated — rows updated in InnoDB
mysql.innodb_rows_deleted — rows deleted from InnoDB
mysql.slow_queries — cumulative slow query count
mysql.table_locks_waited — table-level lock contention counter
mysql.bytes_sent — network bytes sent

Each metric is returned as a single (timestamp_ms, value) row for live charting.

Instance Inspector

Exposes tabular snapshots of running server state:

mysql.processlist — active sessions from information_schema.PROCESSLIST (user, host, db, command, time, state, info)

Limitations

SQL-only driver; it does not expose document or key-value APIs.
Instance metrics return a single data point per call (current snapshot from SHOW GLOBAL STATUS), not a historical time series. Cumulative counters (e.g. mysql.bytes_sent) grow monotonically — interpret them as deltas between samples rather than absolute rates.
The performance_schema availability probe runs once at catalog construction time. When performance_schema is absent, performance-schema-specific metrics are omitted from list_metrics(). The static metric set (SHOW GLOBAL STATUS based) is always available.
A multi-statement script runs each statement sequentially rather than as one atomic server-side batch; statement splitting is text-based and may missplit stored-program bodies that embed ; (e.g. CREATE PROCEDURE ... BEGIN ... END).
Cancellation depends on server permissions and connection state when KILL QUERY is issued.
Code generation is scoped to supported MySQL/MariaDB constructs; unsupported generator IDs return NotSupported.
Routine listing covers only FUNCTION and PROCEDURE types. MySQL aggregate functions (registered via CREATE AGGREGATE FUNCTION UDF plugin) and window functions are not surfaced in information_schema.ROUTINES and are therefore not listed.
SHOW CREATE FUNCTION/SHOW CREATE PROCEDURE requires the SHOW_ROUTINE privilege (MySQL 8.0+) or ownership of the routine; without sufficient privileges the definition column returns NULL and the viewer displays a notice instead of the source.

DDL Capabilities

Non-Transactional DDL

CRITICAL: MySQL DDL operations are NOT transactional — they cannot be rolled back:

BEGIN;
ALTER TABLE users ADD COLUMN phone VARCHAR(20) NULL;
-- DDL is committed immediately, ROLLBACK has no effect!
ROLLBACK;  -- Too late, column already added

Exception: RENAME TABLE is atomic (safe to use in transactions).

ALTER TABLE Behavior

Table rewrites:

Most ALTER TABLE operations rewrite the entire table (locks table for duration)

Use ALGORITHM=INPLACE and LOCK=NONE for online DDL (MySQL 5.6+):

ALTER TABLE users ADD COLUMN phone VARCHAR(20) NULL, ALGORITHM=INPLACE, LOCK=NONE;

Adding columns:

Adding column at end of table: Fast (metadata-only)
Adding column in middle of table: Table rewrite (locks table)
Use AFTER column_name to control position

Adding columns with defaults:

Table rewrite (locks table)
Default value is written to all existing rows

Changing column types:

Always requires table rewrite (locks table)
Data conversion happens during rewrite

Dropping columns:

Table rewrite (locks table)
Data is immediately deleted

Renaming columns:

Table rewrite (locks table)
May break views, triggers, and application code

Index Operations

CREATE INDEX:

Locks table for writes (reads allowed)

Use ALGORITHM=INPLACE, LOCK=NONE for online index creation:

CREATE INDEX idx_users_email ON users(email) ALGORITHM=INPLACE, LOCK=NONE;

DROP INDEX:

Locks table for writes (reads allowed)
Use ALGORITHM=INPLACE, LOCK=NONE for online index removal

Constraints

Foreign keys:

Adding foreign keys scans both tables (locks both)
Use ALGORITHM=INPLACE, LOCK=NONE when possible

UNIQUE constraints:

Requires index creation (locks table)

CHECK constraints (MySQL 8.0.16+):

Metadata-only (fast)
Validated on INSERT/UPDATE only

Online DDL (MySQL 5.6+)

ALGORITHM options:

INPLACE — Modify table in place (no copy)
COPY — Create new table and copy rows (default for old MySQL versions)
INSTANT — Metadata-only (MySQL 8.0+, limited operations)

LOCK options:

NONE — Allow concurrent reads and writes
SHARED — Allow reads, block writes
EXCLUSIVE — Block reads and writes

Example:

ALTER TABLE users 
  ADD COLUMN phone VARCHAR(20) NULL,
  ALGORITHM=INPLACE,
  LOCK=NONE;

Known Limitations

DDL not transactional (cannot rollback)
Most ALTER TABLE ops rewrite entire table (locks table)
Adding column in middle of table requires rewrite
Online DDL support varies by MySQL version
Use pt-online-schema-change (Percona Toolkit) for zero-downtime DDL on large tables

Best Practices

Test on a copy first — DDL cannot be rolled back
Use online DDL — Add ALGORITHM=INPLACE, LOCK=NONE when supported
Schedule maintenance windows — Run DDL during low-traffic periods
Monitor table size — Large tables take longer to rewrite
Use pt-online-schema-change — For zero-downtime DDL on production tables