MySQL Variables transaction_prealloc_size 数据库 参数变量解释及正确配置使用
本站中文解释
transaction_prealloc_size参数指定了每个事务开始时MySQL服务器中分配给该事务语句的事务缓存空间的大小。这个参数应该根据MySQL服务器的数据库业务类型和量来设置，默认为8192字节。
要改变这个参数的值，可以使用以下命令：
SET GLOBAL transaction_prealloc_size = value;
value可以是整数、字符串或者NULL，以字节为单位。将其设置为0则可取消预先分配空间，而将其设置为NULL则为每个事务分配默认值。
官方英文解释
transaction_prealloc_size
| Command-Line Format | --transaction-prealloc-size=# |
|---|---|
| System Variable | transaction_prealloc_size |
| Scope | Global, Session |
| Dynamic | Yes |
| Type | Integer |
| Default Value | 4096 |
| Minimum Value | 1024 |
| Maximum Value | 131072 |
| Unit | bytes |
| Block Size | 1024 |
There is a per-transaction memory pool from which various
transaction-related allocations take memory. The initial size
of the pool in bytes is
transaction_prealloc_size.
For every allocation that cannot be satisfied from the pool
because it has insufficient memory available, the pool is
increased by
transaction_alloc_block_size
bytes. When the transaction ends, the pool is truncated to
transaction_prealloc_size
bytes.
By making
transaction_prealloc_size
sufficiently large to contain all statements within a single
transaction, you can avoid many malloc()
calls.
