Firebird 锁 "table" 以防止插入

Question

是否可以锁定 table 以防止 inserts/updates/deletes？

我需要锁定 table、删除一些记录和 "reset" 生成器。

>> lock table logs to prevent inserts/updates/deletes;
delete from logs where id <= :lastIdProcessed;
if ((select count(1) from logs) = 0) {
    alter sequence logSequence restart with 0;
}
>> commit and release table

另一个问题是，如果有一个 insert into logs (gen_id(logSequence,1)) 等待锁定释放，我将进入 throwble，插入将运行和 logSequence 使用它之前的值递增它 restart?

Answer 1

根据您的需要，您可以使用

启动快照 table 稳定交易 table 预留

SET TRANSACTION 
    READ WRITE 
    ISOLATION LEVEL SNAPSHOT TABLE STABILITY 
    WAIT
    RESERVING <tablename>, <tablename> FOR PROTECTED WRITE

SNAPSHOT TABLE STABILITY Isolation Level

The SNAPSHOT TABLE STABILITY isolation level is the most restrictive. As in SNAPSHOT, a transaction in SNAPSHOT TABLE STABILITY isolation sees only those changes that were committed before the current transaction was started. After a SNAPSHOT TABLE STABILITY is started, no other transactions can make any changes to any table in the database that has changes pending. Other transactions are able to read other data, but any attempt at inserting, updating or deleting by a parallel process will cause conflict exceptions.

The RESERVING clause can be used to allow other transactions to change data in some tables.

If any other transaction has an uncommitted change of data pending in any database table before a transaction with the SNAPSHOT TABLE STABILITY isolation level is started, trying to start a SNAPSHOT TABLE STABILITY transaction will result in an exception.

[..]

RESERVING

The RESERVING clause in the SET TRANSACTION statement reserves tables specified in the table list. Reserving a table prevents other transactions from making changes in them or even, with the inclusion of certain parameters, from reading data from them while this transaction is running.

A RESERVING clause can also be used to specify a list of tables that can be changed by other transactions, even if the transaction is started with the SNAPSHOT TABLE STABILITY isolation level.

One RESERVING clause is used to specify as many reserved tables as required.

有关信息，请参阅末尾的 Transaction Statements for more information; you might also want to consult the old Interbase 6.0 documentation (especially Embedded SQL Guide and Developer's guide, see https://www.firebirdsql.org/en/reference-manuals/。

我没有使用此功能的经验，因此无法就其潜在的缺陷向您提供建议。

Firebird 锁 "table" 以防止插入

Firebird lock "table" to prevent inserts

firebird

locking

transactions

SNAPSHOT TABLE STABILITY Isolation Level

RESERVING