mysql-compatible sql query parsing and resolution
Parses SQL statements using a recursive descent parser that builds an abstract syntax tree (AST), then resolves table references, column names, and function calls against the internal schema system. The resolver validates semantic correctness by cross-referencing the internal table schema (ob_inner_table_schema) and type system before passing to the optimizer. Supports MySQL 5.7+ syntax including window functions, CTEs, and subqueries.
Unique: Implements a two-phase resolution system (parse → semantic resolve) with deep integration into the internal table schema system, enabling schema-aware optimization decisions and supporting both system tables and user-defined tables in a unified framework
vs alternatives: Achieves MySQL compatibility at the parser level rather than via translation layers, reducing latency and enabling native support for distributed query optimization
cost-based query optimization with multi-table join planning
Applies cost-based optimization using cardinality estimation, table statistics, and join order enumeration to generate optimal physical execution plans. The optimizer evaluates multiple join orders (nested loop, hash join, merge join) and access paths (full scan, index scan, partition pruning) using a dynamic programming algorithm. Integrates with the plan cache to avoid re-optimization for identical query patterns.
Unique: Combines dynamic programming join enumeration with partition-aware pruning and distributed execution planning, allowing the optimizer to reason about data locality and parallel execution across tablet replicas
vs alternatives: Outperforms rule-based optimizers on complex joins by using actual statistics; faster than exhaustive enumeration by pruning suboptimal branches early
distributed transaction coordination with two-phase commit
Coordinates multi-tablet transactions using a two-phase commit (2PC) protocol where the transaction coordinator (typically the leader tablet) collects prepare votes from all participating tablets, then issues a global commit or rollback decision. The protocol uses write-ahead logging to ensure durability of the commit decision, and Paxos replication to ensure the decision survives coordinator failures. Supports both strong consistency (all-or-nothing) and eventual consistency modes for performance tuning.
Unique: Implements 2PC with Paxos-replicated commit decisions, ensuring that the commit decision survives coordinator failures without requiring a separate consensus service
vs alternatives: Provides stronger consistency than eventual consistency approaches; more efficient than three-phase commit because it assumes fail-stop failures
partition pruning and predicate pushdown for query optimization
Analyzes WHERE clause predicates during query optimization to identify which tablet partitions contain matching rows, then prunes partitions that cannot contain results. Pushes filter predicates down to the storage layer so that filtering happens during table scans rather than after rows are retrieved. Supports range pruning (for range-partitioned tables), hash pruning (for hash-partitioned tables), and list pruning (for list-partitioned tables). Integrates with the query optimizer to apply pruning before generating the execution plan.
Unique: Integrates partition pruning into the cost-based optimizer rather than as a separate pass, allowing pruning decisions to influence join order and access path selection
vs alternatives: More effective than static partition elimination because it handles dynamic predicates at runtime; more efficient than post-scan filtering because pruning happens before data is retrieved
adaptive query execution with runtime statistics collection
Collects runtime statistics during query execution (rows processed, actual join cardinalities, predicate selectivity) and uses these statistics to adapt the execution plan mid-query. If actual cardinalities differ significantly from estimates, the executor can switch to a different join algorithm or access path without restarting the query. Statistics are fed back to the plan cache to improve future plan quality. Integrates with the SQL audit system (ob_gv_sql_audit) to track execution metrics.
Unique: Implements mid-query plan adaptation by monitoring actual cardinalities and switching join algorithms without restarting, using buffered intermediate results to enable seamless transitions
vs alternatives: More responsive than static plan optimization because it adapts to actual data at runtime; more efficient than re-optimization because it avoids query restart overhead
tenant isolation with resource quotas and multi-tenancy support
Isolates multiple tenants within a single OceanBase cluster using logical tenant boundaries, resource quotas (CPU, memory, I/O), and access control lists. Each tenant has its own schema, data, and configuration, but shares underlying hardware resources. The resource manager enforces quotas by throttling queries that exceed allocated resources. Integrates with the session context to track tenant identity and apply tenant-specific configuration.
Unique: Implements tenant isolation at the session and query execution level, allowing multiple tenants to share the same cluster while enforcing logical separation and resource quotas
vs alternatives: More efficient than separate database instances because resources are shared; more flexible than row-level security because isolation is enforced at the session level
distributed sql execution with tablet-aware data routing
Executes physical plans across multiple tablet replicas by decomposing queries into remote RPC calls via the RPC communication framework. The executor routes data requests to the correct tablet partition based on the partition key, handles remote execution failures with automatic retry logic, and merges results from multiple tablets. Uses the ObRpcProcessor framework to serialize/deserialize query fragments and coordinate execution across nodes.
Unique: Integrates tablet metadata (partition key ranges, replica locations) directly into the execution engine, enabling partition pruning at plan time and dynamic tablet discovery at runtime via the RPC framework
vs alternatives: Achieves transparent distribution without application-level sharding logic; faster than query-time routing because partition decisions are made during optimization
mvcc-based snapshot isolation with multi-version row storage
Implements multi-version concurrency control (MVCC) using row-level versioning where each row modification creates a new version with a transaction ID (txn_id) and commit timestamp. Readers acquire a consistent snapshot at a specific timestamp and only see versions committed before that timestamp, enabling concurrent reads and writes without blocking. The transaction manager maintains active transaction lists and coordinates version visibility across the cluster using the Paxos consensus protocol.
Unique: Combines row-level versioning with Paxos-based timestamp ordering to achieve snapshot isolation across distributed tablets without global locks, using undo logs for version reconstruction rather than storing all versions inline
vs alternatives: Provides stronger isolation guarantees than optimistic locking while avoiding the latency of pessimistic locking; more efficient than full version storage by using undo logs for historical reconstruction
+6 more capabilities