MonetDB的SQL手册——Trace子句

 

A performance trace can be obtained using the TRACE statement modifier. It collects all the trace information in a table reproduced by tracelog(), which can be queried using ordinary SQL statements. The internal trace table is reset at each query being traced. Its definition is given below:

TRACE字句可以跟踪性能，tracelog()收集表处理过程的信息。可以使用sql查询。定义如下：

create function tracelog()
    returns table (
        event integer,      -- event counter
        clk varchar(20),    -- wallclock, no mtime in kernel
        pc varchar(50),     -- module.function[nr]
        thread int,         -- thread identifier
        "user" int,             -- client identifier
        ticks integer,      -- time in microseconds
        reads integer,      -- number of blocks read
        writes integer,     -- number of blocks written
        rbytes integer,     -- amount of bytes touched
        wbytes integer,     -- amount of bytes written
        type string,        -- return types
        stmt string         -- actual statement executed
    )
    external name sql.dump_trace;