log_min_messages：控制服务器日志级别，总控参数，log_min_error_statement要大于等于log_min_messages时，SQL语句才会被记录（默认ERROR，足够）。默认是WARNING，每个级别的定义如下：
log_min_duration_statement：本质上的作用是记录慢日志，记录信息少，建议使用https://www.postgresql.org/docs/current/auto-explain.html（LightDB默认采用此）。log_duration则是为每个SQL语句记录执行时长，非常的耗性能，如果客户端使用扩展查询协议，则会记录解析、绑定、执行三个阶段的时间。所以，一般生产应该开log_min_duration_statement，关log_duration。
log_error_verbosity：log_min_messages控制了级别，log_error_verbosity控制对于每个要记录的日志，记录的详细程度，例如上下文、参数等，取值为TERSE, DEFAULT, 和VERBOSE。TERSE比DEFAULT少DETAIL, HINT, QUERY, CONTEXT，VERBOSE记录了SQLSTATE错误码以及记录日志的函数、c源文件名、以及行号，类似LOG4J。其实现在elog.c send_message_to_server_log方法中，详细的错误日志结构体为struct ErrorData。如下：
/* * ErrorData holds the data accumulated during any one ereport() cycle. * Any non-NULL pointers must point to palloc'd data. * (The const pointers are an exception; we assume they point at non-freeable * constant strings.) */ typedef struct ErrorData { int elevel; /* error level */ bool output_to_server; /* will report to server log? */ bool output_to_client; /* will report to client? */ bool show_funcname; /* true to force funcname inclusion */ bool hide_stmt; /* true to prevent STATEMENT: inclusion */ bool hide_ctx; /* true to prevent CONTEXT: inclusion */ const char *filename; /* __FILE__ of ereport() call */ int lineno; /* __LINE__ of ereport() call */ const char *funcname; /* __func__ of ereport() call */ const char *domain; /* message domain */ const char *context_domain; /* message domain for context message */ int sqlerrcode; /* encoded ERRSTATE */ char *message; /* primary error message (translated) */ char *detail; /* detail error message */ char *detail_log; /* detail error message for server log only */ char *hint; /* hint message */ char *context; /* context message */ char *backtrace; /* backtrace */ const char *message_id; /* primary message's id (original string) */ char *schema_name; /* name of schema */ char *table_name; /* name of table */ char *column_name; /* name of column */ char *datatype_name; /* name of datatype */ char *constraint_name; /* name of constraint */ int cursorpos; /* cursor index into query string */ int internalpos; /* cursor index into internalquery */ char *internalquery; /* text of internally-generated query */ int saved_errno; /* errno at entry */ /* context containing associated non-constant strings */ struct MemoryContextData *assoc_context; } ErrorData;
/* * Write error report to server's log */ static void send_message_to_server_log(ErrorData *edata) { StringInfoData buf; initStringInfo(&buf); saved_timeval_set = false; formatted_log_time[0] = ' '; log_line_prefix(&buf, edata); appendStringInfo(&buf, "%s: ", _(error_severity(edata->elevel))); if (Log_error_verbosity >= PGERROR_VERBOSE) appendStringInfo(&buf, "%s: ", unpack_sql_state(edata->sqlerrcode)); if (edata->message) append_with_tabs(&buf, edata->message); else append_with_tabs(&buf, _("missing error text")); if (edata->cursorpos > 0) appendStringInfo(&buf, _(" at character %d"), edata->cursorpos); else if (edata->internalpos > 0) appendStringInfo(&buf, _(" at character %d"), edata->internalpos); appendStringInfoChar(&buf, ' '); if (Log_error_verbosity >= PGERROR_DEFAULT) { if (edata->detail_log) { log_line_prefix(&buf, edata); appendStringInfoString(&buf, _("DETAIL: ")); append_with_tabs(&buf, edata->detail_log); appendStringInfoChar(&buf, ' '); } else if (edata->detail) { log_line_prefix(&buf, edata); appendStringInfoString(&buf, _("DETAIL: ")); append_with_tabs(&buf, edata->detail); appendStringInfoChar(&buf, ' '); } if (edata->hint) { log_line_prefix(&buf, edata); appendStringInfoString(&buf, _("HINT: ")); append_with_tabs(&buf, edata->hint); appendStringInfoChar(&buf, ' '); } if (edata->internalquery) { log_line_prefix(&buf, edata); appendStringInfoString(&buf, _("QUERY: ")); append_with_tabs(&buf, edata->internalquery); appendStringInfoChar(&buf, ' '); } if (edata->context && !edata->hide_ctx) { log_line_prefix(&buf, edata); appendStringInfoString(&buf, _("CONTEXT: ")); append_with_tabs(&buf, edata->context); appendStringInfoChar(&buf, ' '); } if (Log_error_verbosity >= PGERROR_VERBOSE) { /* assume no newlines in funcname or filename... */ if (edata->funcname && edata->filename) { log_line_prefix(&buf, edata); appendStringInfo(&buf, _("LOCATION: %s, %s:%d "), /*记录发生位置*/ edata->funcname, edata->filename, edata->lineno); } else if (edata->filename) { log_line_prefix(&buf, edata); appendStringInfo(&buf, _("LOCATION: %s:%d "), edata->filename, edata->lineno); } } if (edata->backtrace) { log_line_prefix(&buf, edata); appendStringInfoString(&buf, _("BACKTRACE: ")); append_with_tabs(&buf, edata->backtrace); appendStringInfoChar(&buf, ' '); } }
示例
2021-08-28 18:53:24.959351T pgbench zjh@postgres localhost(40546) client backend idle 00000 [2021-08-28 18:53:24 CST] 0 [143033] DEBUG: 00000: StartTransaction(1) name: unnamed; blockState:
DEFAULT; state: INPROGRESS, xid/subid/cid: 0/1/0
2021-08-28 18:53:24.959351T pgbench zjh@postgres localhost(40546) client backend idle 00000 [2021-08-28 18:53:24 CST] 0 [143033] LOCATION: ShowTransactionStateRec, xact.c:5351
2021-08-28 18:53:24.959351T pgbench zjh@postgres localhost(40546) client backend idle 00000 [2021-08-28 18:53:24 CST] 0 [143033] STATEMENT: begin
2021-08-28 18:53:24.959379T pgbench zjh@postgres localhost(40546) client backend idle 00000 [2021-08-28 18:53:24 CST] 0 [143033] LOG: 00000: statement: begin
2021-08-28 18:53:24.959379T pgbench zjh@postgres localhost(40546) client backend idle 00000 [2021-08-28 18:53:24 CST] 0 [143033] LOCATION: exec_simple_query, postgres.c:1044
2021-08-28 18:53:24.959403T pgbench zjh@postgres localhost(40546) client backend BEGIN 00000 [2021-08-28 18:53:24 CST] 0 [143033] LOG: 00000: parse tree:
2021-08-28 18:53:24.959403T pgbench zjh@postgres localhost(40546) client backend BEGIN 00000 [2021-08-28 18:53:24 CST] 0 [143033] DETAIL: {QUERY
:commandType 5
:querySource 0
:canSetTag true
:utilityStmt ?
:resultRelation 0
:hasAggs false
:hasWindowFuncs false
:hasTargetSRFs false
:hasSubLinks false
:hasDistinctOn false
:hasRecursive false
:hasModifyingCTE false
:hasForUpdate false
:hasRowSecurity false
:cteList <>
:rtable <>
:jointree <>
:targetList <>
:override 0
:onConflict <>
:returningList <>
:groupClause <>
:groupingSets <>
:havingQual <>
:windowClause <>
:distinctClause <>
:sortClause <>
:limitOffset <>
:limitCount <>
:limitOption 0
:rowMarks <>
:setOperations <>
:constraintDeps <>
:withCheckOptions <>
:stmt_location 0
:stmt_len 0
}
2021-08-28 18:53:24.959403T pgbench zjh@postgres localhost(40546) client backend BEGIN 00000 [2021-08-28 18:53:24 CST] 0 [143033] LOCATION: elog_node_display, print.c:85
2021-08-28 19:01:46.087410T @ autovacuum worker 00000 [2021-08-28 19:01:45 CST] 0 [143957] DEBUG: 00000: "pgbench_history": found 0 removable, 21724 nonremovable row versions in 139 out of 139 pages 2021-08-28 19:01:46.087410T @ autovacuum worker 00000 [2021-08-28 19:01:45 CST] 0 [143957] DETAIL: 0 dead row versions cannot be removed yet, oldest xmin: 23145 There were 0 unused item identifiers. Skipped 0 pages due to buffer pins, 0 frozen pages. 0 pages are entirely empty. CPU: user: 0.01 s, system: 0.00 s, elapsed: 0.01 s. 2021-08-28 19:01:46.087410T @ autovacuum worker 00000 [2021-08-28 19:01:45 CST] 0 [143957] CONTEXT: while scanning relation "public.pgbench_history"
LightDB 21.3将增加参数 log_retention_days 控制自动清理日志文件
参考：
pg日志总结详解 https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_LogAccess.Concepts.PostgreSQL.html
https://www.postgresql.org/docs/current/runtime-config-logging.html