企业网站建设存在的典型问题有哪些?,wordpress的后台,itc会议系统,扒wordpress最近跟朋友讨论到PostgreSQL日志中的SQL记录时机#xff0c;研究了下log_statement 和 log_min_duration_statement两个参数#xff0c;记录一下。 一、 参数简介
1. log_statement
① 作用
控制记录SQL的类型#xff0c;可选值为#xff1a;
none#xff1a;关闭研究了下log_statement 和 log_min_duration_statement两个参数记录一下。 一、 参数简介
1. log_statement
① 作用
控制记录SQL的类型可选值为
none关闭默认ddlDDL语句modDDL和所有涉及数据修改的语句DML、COPY FROM、PREPARE、EXECUTE等。对于explain和explain analyze如果后面的语句类型符合也会被记录all所有语句
② 记录时机 SQL语句解析成功后执行前。因此即使设置为all也不会记录有语法错误的语句如果想记录应该使用log_min_error_statement参数。
③ 记录内容 记录SQL语句包含参数但不包含执行用户、主机名等信息这些需要审计插件才有。 2. log_min_duration_statement
① 作用
记录超过指定执行时间阈值的SQL可选值为
-1关闭默认0所有语句正数慢SQL阈值
② 记录时机 SQL语句执行完成后因此能记录到执行时间。
③ 记录内容
记录SQL语句、执行时间但不包含参数。对于使用扩展查询协议的客户端对语法分析、绑定、执行每一步所花时间会独立记录。 3. 同时符合两者的SQL会如何
语句在解析完成后、执行开始前即被记入日志log_statement生效语句执行完成后单独将duration记入日志log_min_duration_statement生效但不再重复记录语句因此建议使用log_line_prefix记录PID或会话ID避免duration和语句关联不上 二、 效果测试
1. 两者均设置
log_statementall,log_min_duration_statement0s 2023-11-28 17:51:45.222 CST [2484] LOG: statement: select pg_sleep(10); 2023-11-28 17:51:55.227 CST [2484] LOG: duration: 10005.249 ms 语句记录为开始时间log_statement生效duration在执行完成时单独记录log_min_duration_statement生效但不再重复记录语句。 2. 仅设置log_statement
log_statementall,log_min_duration_statement-1禁用 2023-11-28 17:53:49.540 CST [2760] LOG: statement: select pg_sleep(10); 仅记录语句记录时间为开始时间没有duration 3. 仅设置log_min_duration_statement
log_statementnone禁用,log_min_duration_statement0s 2023-11-28 17:55:20.288 CST [2826] LOG: duration: 15015.447 ms statement: select pg_sleep(15); 记录语句和duration记录时间为结束时间 三、 参数记录时机 从上面文档可以知道两个参数记录时机都在SQL执行阶段只是一个在前一个在后。源码中SQL执行相关的函数主要是exec_simple_query因此我们就看看这个函数。 函数刚开头就可以看到 pg_parse_query 和 check_log_statement函数。
/** exec_simple_query** Execute a simple Query protocol message.*/
static void
exec_simple_query(const char *query_string)
{CommandDest dest whereToSendOutput;MemoryContext oldcontext;List *parsetree_list;ListCell *parsetree_item;bool save_log_statement_stats log_statement_stats;bool was_logged false;bool use_implicit_block;char msec_str[32];
.../** Do basic parsing of the query or queries (this should be safe even if* we are in aborted transaction state!)*/parsetree_list pg_parse_query(query_string);/* Log immediately if dictated by log_statement */if (check_log_statement(parsetree_list)){ereport(LOG,(errmsg(statement: %s, query_string),errhidestmt(true),errdetail_execute(parsetree_list)));was_logged true;}
pg_parse_query函数用于SQL解析符合log_statement记录的语句发生在解析完成后check_log_statement函数就用于检查log_statement的设置标记是否需要记录was_loggedtrue表示已记录SQL语句主要是给后面的慢SQL记录函数提示其不需重复记录SQL文本
/** check_log_statement* Determine whether command should be logged because of log_statement** stmt_list can be either raw grammar output or a list of planned* statements*/
static bool
check_log_statement(List *stmt_list)
{ListCell *stmt_item;if (log_statement LOGSTMT_NONE)return false;if (log_statement LOGSTMT_ALL)return true;/* Else we have to inspect the statement(s) to see whether to log */foreach(stmt_item, stmt_list){Node *stmt (Node *) lfirst(stmt_item);if (GetCommandLogLevel(stmt) log_statement)return true;}return false;
} 后面一大堆是SQL执行相关的代码非本次重点直接拉到函数末尾可以看到check_log_duration函数看名字都能猜到是它了也符合在SQL执行完才记录。
.../** Emit duration logging if appropriate.*/switch (check_log_duration(msec_str, was_logged)){case 1:ereport(LOG,(errmsg(duration: %s ms, msec_str),errhidestmt(true)));break;case 2:ereport(LOG,(errmsg(duration: %s ms statement: %s,msec_str, query_string),errhidestmt(true),errdetail_execute(parsetree_list)));break;}if (save_log_statement_stats)ShowUsage(QUERY STATISTICS);TRACE_POSTGRESQL_QUERY_DONE(query_string);debug_query_string NULL;
} check_log_duration函数 可以看到注释中给出了上面case 1,2的含义
1仅记录duration即前面提到的两个参数均生效的场景2记录duration和语句即前面提到的仅log_min_duration_statement生效的场景
另外是否记录慢sql与 log_duration、log_min_duration_sample 这些参数也有关。
/** check_log_duration* Determine whether current commands duration should be logged* We also check if this statement in this transaction must be logged* (regardless of its duration).** Returns:* 0 if no logging is needed* 1 if just the duration should be logged* 2 if duration and query details should be logged** If logging is needed, the duration in msec is formatted into msec_str[],* which must be a 32-byte buffer.** was_logged should be true if caller already logged query details (this* essentially prevents 2 from being returned).*/
int
check_log_duration(char *msec_str, bool was_logged)
{if (log_duration || log_min_duration_sample 0 ||log_min_duration_statement 0 || xact_is_sampled){long secs;int usecs;int msecs;bool exceeded_duration;bool exceeded_sample_duration;bool in_sample false;TimestampDifference(GetCurrentStatementStartTimestamp(),GetCurrentTimestamp(),secs, usecs);msecs usecs / 1000;/** This odd-looking test for log_min_duration_* being exceeded is* designed to avoid integer overflow with very long durations: dont* compute secs * 1000 until weve verified it will fit in int.*/exceeded_duration (log_min_duration_statement 0 ||(log_min_duration_statement 0 (secs log_min_duration_statement / 1000 ||secs * 1000 msecs log_min_duration_statement)));exceeded_sample_duration (log_min_duration_sample 0 ||(log_min_duration_sample 0 (secs log_min_duration_sample / 1000 ||secs * 1000 msecs log_min_duration_sample)));/** Do not log if log_statement_sample_rate 0. Log a sample if* log_statement_sample_rate 1 and avoid unnecessary random() call* if log_statement_sample_rate 1.*/if (exceeded_sample_duration)in_sample log_statement_sample_rate ! 0 (log_statement_sample_rate 1 ||random() log_statement_sample_rate * MAX_RANDOM_VALUE);if (exceeded_duration || in_sample || log_duration || xact_is_sampled){snprintf(msec_str, 32, %ld.%03d,secs * 1000 msecs, usecs % 1000);if ((exceeded_duration || in_sample || xact_is_sampled) !was_logged)return 2;elsereturn 1;}}return 0;
} 参考
https://www.postgresql.org/docs/current/runtime-config-logging.html#GUC-LOG-STATEMENT https://www.postgresql.org/docs/current/protocol-flow.html#PROTOCOL-FLOW-EXT-QUERY https://blog.csdn.net/qq_35423190/article/details/129138740 https://iwmj.wordpress.com/2018/04/03/postgresql-%E5%89%8D%E5%90%8E%E7%AB%AF%E5%8D%8F%E8%AE%AE%E4%B8%AD%E7%9A%84%E6%9F%A5%E8%AF%A2%E6%96%B9%E5%BC%8F%EF%BC%9A%E7%AE%80%E5%8D%95%E6%9F%A5%E8%AF%A2%E3%80%81%E6%89%A9%E5%B1%95%E6%9F%A5%E8%AF%A2/
