PolarDB-X Standard Edition (X-Cluster)

Operational guidance and best practices for PolarDB-X 2.0 Standard Edition. Standard Edition is 100% MySQL compatible — use standard MySQL syntax for all SQL tasks.

Scope

Applies to:

PolarDB-X 2.0 Standard Edition (X-Cluster based)

Not applicable to:

PolarDB-X 2.0 Enterprise Edition (Distributed Edition) — use polardbx-sql skill
PolarDB-X 1.0 (DRDS 1.0)

Identify instance type via SELECT VERSION();:

Contains X-Cluster (e.g. 8.0.32-X-Cluster-8.4.20-20251017) -> Standard Edition, this skill applies. NOTE: "X-Cluster" is the official version marker for Standard Edition. The "Cluster" here refers to Standard Edition's own 3-node X-Paxos cluster (Leader / Follower / Logger), NOT a distributed "Cluster Edition". Do NOT misinterpret it as Enterprise Edition.
Contains TDDL (e.g. 5.7.25-TDDL-5.4.19-20251031) -> Enterprise Edition (Distributed Edition). HARD STOP — you MUST refuse: Do NOT provide any Enterprise Edition advice (no partition design, no GSI, no distributed SQL). Respond only with: "Your instance is PolarDB-X 2.0 Enterprise Edition. This skill covers Standard Edition only. Please use the polardbx-sql skill for Enterprise Edition partition design and SQL guidance." Then stop. Do NOT continue even if the user insists.

CRITICAL: "X-Cluster" Means Standard Edition, NOT Distributed

Users often confuse "X-Cluster" with a distributed/cluster edition. You MUST correct this misconception immediately:

X-Cluster in the version string = Standard Edition. The "Cluster" refers to the internal 3-node X-Paxos consensus cluster (Leader / Follower / Logger) for high availability. It is NOT a distributed data cluster.
Standard Edition supports MySQL native partitioning (RANGE, LIST, HASH, KEY), but does NOT support Enterprise Edition-specific partition functions, distributed sharding, or GSI/CCI syntax.
When a user asks "is X-Cluster the distributed edition?" or "should I use partition design with X-Cluster?", answer clearly: No. X-Cluster is Standard Edition. Use MySQL native partition syntax (PARTITION BY RANGE/LIST/HASH/KEY), not Enterprise Edition distributed partition syntax.
Do NOT mention Enterprise Edition-specific features (distributed partition keys, GSI, CCI, auto-partition, table groups) in your answer — this confuses users into thinking they have those capabilities.

Core Workflow (Follow each time)

Confirm the user has a Standard Edition instance. If not, use polardbx-zero skill to create a free temporary instance (2C4G, 30-day expiry).
Run SELECT VERSION(); to verify Standard Edition (must contain X-Cluster). If the result contains TDDL instead, this is Enterprise Edition — HARD STOP: refuse and redirect to polardbx-sql skill. Do NOT provide any advice.
Identify the operation type and refer to the corresponding section below.
For SQL questions: Standard Edition is 100% MySQL compatible — use MySQL syntax directly, no special adaptation needed.

Key Features Quick Reference

X-Paxos HA

Multi-replica high availability based on X-Paxos consensus protocol. At most one Leader handles all writes; Followers participate in majority voting. Automatic failover with RPO=0 (zero data loss). Performance comparable to MySQL semi-synchronous replication.

Three essential monitoring views (always mention all three by name when discussing cluster health):

INFORMATION_SCHEMA.ALISQL_CLUSTER_GLOBAL — Cluster topology (all nodes' roles, sync progress). IMPORTANT: Only returns data on the Leader node; returns empty result set on Follower/Logger nodes. If you get empty results, you are likely connected to a Follower — reconnect to the Leader.
INFORMATION_SCHEMA.ALISQL_CLUSTER_LOCAL — Current node's local status. Key fields: CURRENT_LEADER (shows which node is Leader), INSTANCE_TYPE (Normal or Log). Use this to identify the current Leader address before querying ALISQL_CLUSTER_GLOBAL.
INFORMATION_SCHEMA.ALISQL_CLUSTER_HEALTH — Replication health metrics. Key fields: LOG_DELAY_NUM (log shipping lag), APPLY_DELAY_NUM (log apply lag), APPLY_DELAY_SECONDS.

-- Step 1: Check local status and find the Leader address
SELECT * FROM INFORMATION_SCHEMA.ALISQL_CLUSTER_LOCAL;
-- Step 2: Cluster topology (must run on Leader node, returns empty on Followers)
SELECT * FROM INFORMATION_SCHEMA.ALISQL_CLUSTER_GLOBAL;
-- Step 3: Replication health
SELECT * FROM INFORMATION_SCHEMA.ALISQL_CLUSTER_HEALTH;

Lizard Transaction System

SCN (System Commit Number) based MVCC replacing InnoDB's native transaction visibility. Write transactions commit by writing SCN to a Transaction Slot; read transactions compare record SCN against a single-number Vision (no active transaction ID array). Supports FlashBack Query via SCN.

Performance vs MySQL 8.0.32 (Sysbench RW, 512 concurrency): 30% higher throughput, 53% lower latency.

Panda Index

Deadlock-free unique key index. Eliminates Gap locks under RC isolation by optimizing constraint checks to row-level lock granularity. No performance overhead; 28 extra bytes per unique index record.

-- Enable (session or global, no restart needed)
SET opt_index_format_panda_enabled = ON;

Default ON for instances created after 2025-06-04.
Requires storage node version >= xcluster8.4.20-20250527.
Only optimizes RC isolation; RR still uses Next-Key locks.
Existing indexes need manual rebuild (see panda-index.md).

100% MySQL Compatible

Full support for stored procedures, triggers, EVENTs, etc. Use standard MySQL syntax for all SQL tasks.

References

Reference	Description
references/x-paxos-ha.md	X-Paxos HA: architecture, log fusion, automatic failover, cluster monitoring SQL
references/lizard-transaction.md	Lizard transaction system: SCN-based MVCC, Cleanout optimization, performance benchmark
references/panda-index.md	Panda Index: deadlock-free unique key, enable/disable, upgrade existing indexes, FAQ

Playbooks

Executable end-to-end verification steps. Agent should auto-execute all steps when instructed to "follow the instructions".

Playbook	Description
playbooks/test-panda-index.md	Verify Panda Index eliminates Gap locks: baseline with regular unique key, then verify with Panda Index

polardbx-standard