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] = '\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, '\n');
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, '\n');
}
else if (edata->detail)
{
log_line_prefix(&buf, edata);
appendStringInfoString(&buf, _("DETAIL: "));
append_with_tabs(&buf, edata->detail);
appendStringInfoChar(&buf, '\n');
}
if (edata->hint)
{
log_line_prefix(&buf, edata);
appendStringInfoString(&buf, _("HINT: "));
append_with_tabs(&buf, edata->hint);
appendStringInfoChar(&buf, '\n');
}
if (edata->internalquery)
{
log_line_prefix(&buf, edata);
appendStringInfoString(&buf, _("QUERY: "));
append_with_tabs(&buf, edata->internalquery);
appendStringInfoChar(&buf, '\n');
}
if (edata->context && !edata->hide_ctx)
{
log_line_prefix(&buf, edata);
appendStringInfoString(&buf, _("CONTEXT: "));
append_with_tabs(&buf, edata->context);
appendStringInfoChar(&buf, '\n');
}
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\n"), /*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\n"),
edata->filename, edata->lineno);
}
}
if (edata->backtrace)
{
log_line_prefix(&buf, edata);
appendStringInfoString(&buf, _("BACKTRACE: "));
append_with_tabs(&buf, edata->backtrace);
appendStringInfoChar(&buf, '\n');
}
}
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
LightDB Enterprise Postgres--金融级关系型数据库,更快、更稳、更懂金融！