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chore[ci skip]: improve code comments

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a631807682 2022-08-14 21:56:52 +08:00
parent 98297034da
commit 6b0b6ff8f8
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1 changed files with 3 additions and 2 deletions
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prepare_stmt.go
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@ -79,8 +79,9 @@ func (db *PreparedStmtDB) prepare(ctx context.Context, conn ConnPool, isTransact
// prepare completed
defer close(cacheStmt.prepared)
// Reason why cannot lock conn.PrepareContext (suppose the maxopen is 1).
// 1. g1 begin tx, now `db.ConnPool` db.numOpen == 1
// Reason why cannot lock conn.PrepareContext
// suppose the maxopen is 1, g1 is creating record and g2 is querying record.
// 1. g1 begin tx, g1 is requeued because of waiting for the system call, now `db.ConnPool` db.numOpen == 1.
// 2. g2 select lock `conn.PrepareContext(ctx, query)`, now db.numOpen == db.maxOpen , wait for release.
// 3. g1 tx exec insert, wait for unlock `conn.PrepareContext(ctx, query)` to finish tx and release.
stmt, err := conn.PrepareContext(ctx, query)