一、postgresql數據庫出現鎖表問題排查
1 //查詢鎖表的情況 2 SELECT
3 A.locktype, 4 A.DATABASE, 5 A.pid, 6 A.relation, 7 b.relname 8 FROM 9 pg_locks 10 A JOIN pg_class b ON A.relation = b.oid;
11 12 //殺死進程 13 select pg_terminate_backend(pid); //pid為進程id號
//用於查詢系統進程狀態的表
select * from pg_stat_activity;
主要關注waiting 是否等待中，stat 進程狀態， query 具體語句
當waiting 為t 的進行需要特別注意，query可以查看到具體語句，然后進行查殺
最終的原因排查為，mq擁堵導致一些流程走不了，代碼流程又涉及到更新等操作，產生數據庫鎖 一直占用着連接的資源 。
二、鎖類型 8種：(pgsql源碼的src/include/storage/lock.h文件)
/* NoLock is not a lock mode, but a flag value meaning "don't get a lock" */ #define NoLock 0 #define AccessShareLock 1 /* SELECT */ #define RowShareLock 2 /* SELECT FOR UPDATE/FOR SHARE */ #define RowExclusiveLock 3 /* INSERT, UPDATE, DELETE */ #define ShareUpdateExclusiveLock 4 /* VACUUM (non-FULL),ANALYZE, CREATE * INDEX CONCURRENTLY */ #define ShareLock 5 /* CREATE INDEX (WITHOUT CONCURRENTLY) */ #define ShareRowExclusiveLock 6 /* like EXCLUSIVE MODE, but allows ROW * SHARE */ #define ExclusiveLock 7 /* blocks ROW SHARE/SELECT...FOR * UPDATE */ #define AccessExclusiveLock 8 /* ALTER TABLE, DROP TABLE, VACUUM * FULL, and unqualified LOCK TABLE */
三、鎖沖突（可以看出哪些鎖會發生沖突）
四、可加鎖對象的定義(pgsql源碼src/include/storage/lock.h文件)
1 typedef enum LockTagType 2 { 3 LOCKTAG_RELATION, /* whole relation */ 4 /* ID info for a relation is DB OID + REL OID; DB OID = 0 if shared */ 5 LOCKTAG_RELATION_EXTEND, /* the right to extend a relation */ 6 /* same ID info as RELATION */ 7 LOCKTAG_PAGE, /* one page of a relation */ 8 /* ID info for a page is RELATION info + BlockNumber */ 9 LOCKTAG_TUPLE, /* one physical tuple */ 10 /* ID info for a tuple is PAGE info + OffsetNumber */ 11 LOCKTAG_TRANSACTION, /* transaction (for waiting for xact done) */ 12 /* ID info for a transaction is its TransactionId */ 13 LOCKTAG_VIRTUALTRANSACTION, /* virtual transaction (ditto) */ 14 /* ID info for a virtual transaction is its VirtualTransactionId */ 15 LOCKTAG_OBJECT, /* non-relation database object */ 16 /* ID info for an object is DB OID + CLASS OID + OBJECT OID + SUBID */ 17 18 /* 19 * Note: object ID has same representation as in pg_depend and 20 * pg_description, but notice that we are constraining SUBID to 16 bits. 21 * Also, we use DB OID = 0 for shared objects such as tablespaces. 22 */ 23 LOCKTAG_USERLOCK, /* reserved for old contrib/userlock code */ 24 LOCKTAG_ADVISORY /* advisory user locks */ 25 } LockTagType;