taosd Reference

taosd is the core service of the TDengine database engine, with its configuration file defaulting to /etc/taos/taos.cfg, though it can also be specified at a different path. This section provides a detailed introduction to the command line parameters and configuration parameters within the taosd configuration file.

Command Line Parameters

The command line parameters for taosd are as follows:

• -a <json file>: Specifies a JSON file that contains various configuration parameters for the service at startup, formatted like {"fqdn":"td1"}. For details on configuration parameters, please refer to the next section.
• -c <directory>: Specifies the directory where the configuration file is located.
• -s: Prints SDB information.
• -C: Prints configuration information.
• -e: Specifies an environment variable, formatted like -e 'TAOS_FQDN=td1'.
• -k: Gets the machine code.
• -dm: Enables memory scheduling.
• -V: Prints version information.

Configuration Parameters

note

After modifying configuration file parameters, it is necessary to restart the taosd service or the client application for changes to take effect.

Connection Related

Parameter Name	support version	Parameter Description
firstEp		The endpoint of the first dnode in the cluster to connect to when taosd starts; default value: localhost:6030
secondEp		If firstEp cannot connect, attempt to connect to the second dnode's endpoint in the cluster; default value: none
fqdn		The service address that taosd listens on after startup; default value: the first hostname configured on the server
compressMsgSize		Whether to compress RPC messages; -1: no messages are compressed; 0: all messages are compressed; N (N>0): only messages larger than N bytes are compressed; default value: -1
shellActivityTimer		The duration in seconds for the client to send heartbeats to the mnode; range: 1-120; default value: 3
numOfRpcSessions		The maximum number of RPC connections supported; range: 100-100000; default value: 30000
numOfRpcThreads		The number of threads for RPC data transmission; range: 1-50, default value: half of the CPU cores
numOfTaskQueueThreads		The number of threads for the client to process RPC messages, range: 4-16, default value: half of the CPU cores
rpcQueueMemoryAllowed		The maximum amount of memory allowed for RPC messages received on a dnode; unit: bytes; range: 104857600-INT64_MAX; default value: 1/10 of server memory
resolveFQDNRetryTime	Removed in 3.x	The number of retries when FQDN resolution fails
timeToGetAvailableConn	Removed in 3.3.4.x	The maximum waiting time to obtain an available connection; range: 10-50000000; unit: milliseconds; default value: 500000
maxShellConns	Removed in 3.x	The maximum number of connections allowed to be created
maxRetryWaitTime		The maximum timeout for reconnection; default value: 10s
shareConnLimit	Added in 3.3.4.0	The number of requests that a connection can share; range: 1-512; default value: 10
readTimeout	Added in 3.3.4.0	The minimum timeout for a single request; range: 64-604800; unit: seconds; default value: 900

Monitoring Related

Parameter Name	Parameter Description
monitor	Whether to collect monitoring data and report it; 0: off; 1: on; default value: 0
monitorFqdn	The FQDN of the server where the taosKeeper service is located; default value: none
monitorPort	The port number the taosKeeper service listens on; default value: 6043
monitorInternal	The time interval for recording system parameters (CPU/memory) in the monitoring database; unit: seconds; range: 1-200000; default value: 30
telemetryReporting	Whether to upload telemetry; 0: do not upload; 1: upload; default value: 1
crashReporting	Whether to upload crash information; 0: do not upload; 1: upload; default value: 1

Query Related

Parameter Name	Parameter Description
queryPolicy	Query policy; 1: only use vnode, do not use qnode; 2: sub-tasks without scanning operators execute on qnode, those with scanning operators execute on vnode; 3: vnode only runs scanning operators, other operators run on qnode; 4: use client aggregation mode; default value: 1
maxNumOfDistinctRes	The maximum number of distinct results allowed to be returned; default value: 100,000; maximum allowed value: 100 million
countAlwaysReturnValue	Whether the count/hyperloglog function returns a value when the input data is empty or NULL; 0: returns empty row; 1: returns; when set to 1, if the query contains an INTERVAL clause or uses TSMA, and the corresponding group or window has no data or is NULL, that group or window will not return query results. Note that this parameter should have consistent values on both client and server.

Regional Related

Parameter Name	Parameter Description
timezone	The timezone; default value: the timezone configured on the current server
locale	System locale information and encoding format; default value: dynamically retrieved from the system; if auto-retrieval fails, the user needs to set it in the configuration file or through the API
charset	Character set encoding; default value: automatically retrieved from the system

info

1. To address the issue of writing and querying data across multiple time zones, TDengine uses Unix timestamps (Unix Timestamp) to record and store timestamps. The characteristic of Unix timestamps ensures that at any given moment, regardless of time zone, the generated timestamps are consistent. Note that Unix timestamps are converted and recorded on the client side. To ensure other forms of time conversions on the client are correctly converted to Unix timestamps, the correct timezone needs to be set.

   In Linux/macOS, the client will automatically read the timezone information set by the system. Users can also set the timezone in the configuration file in various ways. For example:

   timezone UTC-8
   timezone GMT-8
   timezone Asia/Shanghai

   All of these are valid formats for setting the timezone to UTC+8. However, note that this format (timezone Asia/Shanghai) is not supported under Windows; it must be written as timezone UTC-8.

   The timezone setting affects the contents of SQL statements for queries and writes that are not in Unix timestamp format (e.g., timestamp strings, the interpretation of the keyword now). For example:

   SELECT count(*) FROM table_name WHERE TS<'2019-04-11 12:01:08';

   In UTC+8, the SQL statement is equivalent to:

   SELECT count(*) FROM table_name WHERE TS<1554955268000;

   In UTC, the SQL statement is equivalent to:

   SELECT count(*) FROM table_name WHERE TS<1554984068000;

   To avoid uncertainty when using string time formats, Unix timestamps can be used directly. Additionally, timestamp strings with time zones can also be used in SQL statements, such as RFC3339 format timestamp strings (e.g., 2013-04-12T15:52:01.123+08:00) or ISO-8601 format timestamp strings (e.g., 2013-04-12T15:52:01.123+0800). The conversion of these two strings to Unix timestamps is not affected by the system's time zone.

2. TDengine provides a special field type nchar for storing wide characters such as Chinese, Japanese, and Korean that are not ASCII encoded. Data written to nchar fields will be encoded in UCS4-LE format and sent to the server. It is important to note that the correctness of the encoding is guaranteed by the client. Therefore, if users want to use nchar fields to store non-ASCII characters like Chinese, Japanese, or Korean, the encoding format of the client must be correctly set.

   Characters input by the client use the current default encoding format of the operating system, which is usually UTF-8 on Linux/macOS systems. Some Chinese systems may use GB18030 or GBK, etc. In Docker environments, the default encoding is POSIX. In Chinese versions of Windows, the encoding is CP936. Clients must ensure that the character set they are using is correctly set to guarantee that data in nchar is accurately converted to UCS4-LE format.

   In Linux/macOS, the naming convention for locales is: <language>_<region>.<charset encoding>, for example: zh_CN.UTF-8, where "zh" stands for Chinese, "CN" represents mainland China, and "UTF-8" denotes the character set. The character set encoding provides guidance for the client to correctly parse local strings. In Linux/macOS, the locale can be set to determine the system's character encoding; because Windows uses a locale format that is not POSIX compliant, it requires another configuration parameter charset to specify the character encoding. The charset parameter can also be used in Linux/macOS to specify the character encoding.

3. If the configuration file does not specify charset, in Linux/macOS, taos will automatically read the system's current locale information at startup and extract the charset encoding format from it. If the automatic reading of locale information fails, it will attempt to read the charset configuration. If reading the charset configuration also fails, the startup process will be interrupted.

   In Linux/macOS, the locale information includes character encoding information, so if the locale of Linux/macOS is set correctly, there is no need to set charset separately. For example:

   locale zh_CN.UTF-8

   In Windows, the system cannot retrieve the current encoding from the locale. If the encoding information cannot be retrieved from the configuration file, taos defaults to CP936 as the character encoding. This is equivalent to adding the following configuration to the configuration file:

   charset CP936

   If you need to adjust the character encoding, please refer to the current operating system's encoding and set it correctly in the configuration file.

   In Linux/macOS, if the user sets both locale and charset and they are inconsistent, the latter will override the former.

   locale zh_CN.UTF-8
   charset GBK

   The effective value of charset is GBK.

   charset GBK
   locale zh_CN.UTF-8

   The effective value of charset is UTF-8.

Storage Related

Parameter Name	Parameter Description
dataDir	Directory for data files; all data files will be written to this directory; default value: /var/lib/taos
tempDir	Specifies the directory for temporary files generated during system operation; default value: /tmp
minimalTmpDirGB	Minimum space required to be preserved in the tempDir specified; unit: GB; default value: 1
minimalDataDirGB	Minimum space required to be preserved in the dataDir specified; unit: GB; default value: 2

Cluster Related

Parameter Name	Parameter Description
supportVnodes	Maximum number of vnodes supported by dnode; range: 0-4096; default value: 2 times the number of CPU cores + 5

Memory Related

Parameter Name	Parameter Description
rpcQueueMemoryAllowed	Maximum amount of memory allowed for rpc messages on a dnode; unit: bytes; range: 10485760-INT64_MAX; default value: 1/10 of server memory
syncLogBufferMemoryAllowed	Maximum amount of memory allowed for sync log buffer messages on a dnode; unit: bytes; range: 10485760-INT64_MAX; default value: 1/10 of server memory; effective from versions 3.1.3.2/3.3.2.13

Performance Tuning

Parameter Name	Parameter Description
numOfCommitThreads	Maximum number of write threads; range: 0-1024; default value: 4

Log Related

Parameter Name	Parameter Description
logDir	Directory for log files; runtime logs will be written to this directory; default value: /var/log/taos
minimalLogDirGB	When the available disk space of the log folder is less than this value, logging will stop; unit: GB; default value: 1
numOfLogLines	Maximum number of lines allowed in a single log file; default value: 10,000,000
asyncLog	Log writing mode; 0: synchronous, 1: asynchronous; default value: 1
logKeepDays	Maximum retention time for log files; unit: days; default value: 0, meaning unlimited retention; log files will not be renamed, and no new log file rolling will occur, but the contents of the log file may continue to roll depending on the size settings; when set to a value greater than 0, if the log file size reaches the set limit, it will be renamed to taosdlog.xxx, where xxx is the timestamp of the last modification of the log file, and a new log file will be rolled
slowLogThreshold	Slow query threshold; if it exceeds or equals the threshold, it is considered a slow query; unit: seconds; default value: 3
slowLogScope	Determines which types of slow queries to log; optional values: ALL, QUERY, INSERT, OTHERS, NONE; default value: ALL
debugFlag	Run log switch; 131 (outputs error and warning logs), 135 (outputs error, warning, and debug logs), 143 (outputs error, warning, debug, and trace logs); default value: 131 or 135 (depending on different modules)
tmrDebugFlag	Timer module log switch; same value range as above
uDebugFlag	Shared function module log switch; same value range as above
rpcDebugFlag	RPC module log switch; same value range as above
jniDebugFlag	JNI module log switch; same value range as above
qDebugFlag	Query module log switch; same value range as above
dDebugFlag	Dnode module log switch; same value range as above; default value 135
vDebugFlag	Vnode module log switch; same value range as above
mDebugFlag	Mnode module log switch; same value range as above
wDebugFlag	WAL module log switch; same value range as above
sDebugFlag	Sync module log switch; same value range as above
tsdbDebugFlag	TSDB module log switch; same value range as above
tqDebugFlag	TQ module log switch; same value range as above
fsDebugFlag	FS module log switch; same value range as above
udfDebugFlag	UDF module log switch; same value range as above
smaDebugFlag	SMA module log switch; same value range as above
idxDebugFlag	Index module log switch; same value range as above
tdbDebugFlag	TDB module log switch; same value range as above

Compression Parameters

Parameter Name	Parameter Description
compressMsgSize	Whether to compress RPC messages; -1: no messages are compressed; 0: all messages are compressed; N (N>0): only messages larger than N bytes are compressed; default value: -1
fPrecision	Sets the compression precision for float type floating-point numbers; range: 0.1 ~ 0.00000001; default value: 0.00000001; float numbers smaller than this value will have their tail truncated
dPrecision	Sets the compression precision for double type floating-point numbers; range: 0.1 ~ 0.0000000000000001; default value: 0.0000000000000001; double numbers smaller than this value will have their tail truncated
lossyColumn	Enables TSZ lossy compression for float and/or double types; range: float, double, none; default value: none; indicates that lossy compression is turned off. Note: This parameter is no longer used in versions 3.3.0.0 and higher.
ifAdtFse	When TSZ lossy compression is enabled, use the FSE algorithm instead of the HUFFMAN algorithm. The FSE algorithm compresses faster but decompresses slightly slower. It can be selected if compression speed is a priority; 0: off, 1: on; default value: 0

Supplementary Notes

1. Effective from versions 3.2.0.0 to 3.3.0.0 (exclusive), enabling this parameter cannot revert back to the version prior to the upgrade.

2. The TSZ compression algorithm uses data prediction techniques for compression, making it more suitable for data that varies in a regular pattern.

3. TSZ compression may take longer; if your server's CPU is largely idle and storage space is limited, it is suitable to opt for this.

4. Example: Enable lossy compression for both float and double types.

   lossyColumns     float|double

5. Configuration changes require a service restart to take effect. If you see the following content in the taosd log upon restarting, it indicates that the configuration has taken effect:

   02/22 10:49:27.607990 00002933 UTL  lossyColumns     float|double

Other Parameters

Parameter Name	Parameter Description
enableCoreFile	Whether to generate a core file upon crash; 0: do not generate; 1: generate; default value: 1; Depending on the startup method, the directory for generated core files is as follows: 1. When started with systemctl start taosd: the core will be generated in the root directory; 2. When started manually, it will be in the directory where taosd is executed.
udf	Whether to start the UDF service; 0: do not start; 1: start; default value: 0
ttlChangeOnWrite	Whether the ttl expiration time changes along with table modifications; 0: do not change; 1: change; default value: 0
tmqMaxTopicNum	Maximum number of topics that can be established for subscription; range: 1-10000; default value: 20
maxTsmaNum	Number of TSMA that can be created in the cluster; range: 0-3; default value: 3

taosd Monitoring Metrics

taosd reports monitoring metrics to taosKeeper, which writes these metrics to the monitoring database, defaulting to log. This section provides a detailed introduction to these monitoring metrics.

taosd_cluster_basic Table

The taosd_cluster_basic table records basic cluster information.

field	type	is_tag	comment
ts	TIMESTAMP		timestamp
first_ep	VARCHAR		Cluster first ep
first_ep_dnode_id	INT		Dnode ID of the cluster's first ep
cluster_version	VARCHAR		TDengine version, e.g., 3.0.4.0
cluster_id	VARCHAR	TAG	cluster id

taosd_cluster_info Table

The taosd_cluster_info table records cluster information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
cluster_uptime	DOUBLE		Current uptime of the master node; unit: seconds
dbs_total	DOUBLE		Total number of databases
tbs_total	DOUBLE		Current total number of tables in the cluster
stbs_total	DOUBLE		Current total number of stable tables
dnodes_total	DOUBLE		Total number of dnodes in the cluster
dnodes_alive	DOUBLE		Total number of alive dnodes in the cluster
mnodes_total	DOUBLE		Total number of mnodes in the cluster
mnodes_alive	DOUBLE		Total number of alive mnodes in the cluster
vgroups_total	DOUBLE		Total number of vgroups in the cluster
vgroups_alive	DOUBLE		Total number of alive vgroups in the cluster
vnodes_total	DOUBLE		Total number of vnodes in the cluster
vnodes_alive	DOUBLE		Total number of alive vnodes in the cluster
connections_total	DOUBLE		Total number of connections in the cluster
topics_total	DOUBLE		Total number of topics in the cluster
streams_total	DOUBLE		Total number of streams in the cluster
grants_expire_time	DOUBLE		Expiration time for authentication, valid for enterprise version, max value for community version
grants_timeseries_used	DOUBLE		Used measuring points
grants_timeseries_total	DOUBLE		Total measuring points, max value for open source version
cluster_id	VARCHAR	TAG	cluster id

taosd_vgroups_info Table

The taosd_vgroups_info table records information about virtual node groups.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
tables_num	DOUBLE		Number of tables in the vgroup
status	DOUBLE		vgroup status, value range: unsynced = 0, ready = 1
vgroup_id	VARCHAR	TAG	vgroup id
database_name	VARCHAR	TAG	Database name the vgroup belongs to
cluster_id	VARCHAR	TAG	cluster id

taosd_dnodes_info Table

The taosd_dnodes_info table records dnode information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
uptime	DOUBLE		dnode uptime; unit: seconds
cpu_engine	DOUBLE		taosd CPU usage, read from /proc/<taosd_pid>/stat
cpu_system	DOUBLE		Server CPU usage, read from /proc/stat
cpu_cores	DOUBLE		Number of CPU cores on the server
mem_engine	DOUBLE		taosd memory usage, read from /proc/<taosd_pid>/status
mem_free	DOUBLE		Available memory on the server; unit: KB
mem_total	DOUBLE		Total memory on the server; unit: KB
disk_used	DOUBLE		Disk usage of the data dir mount; unit: bytes
disk_total	DOUBLE		Total disk capacity of the data dir mount; unit: bytes
system_net_in	DOUBLE		Network throughput, read from /proc/net/dev, received bytes; unit: byte/s
system_net_out	DOUBLE		Network throughput, read from /proc/net/dev, transmitted bytes; unit: byte/s
io_read	DOUBLE		I/O throughput, calculated from rchar read from /proc/<taosd_pid>/io and previous values; unit: byte/s
io_write	DOUBLE		I/O throughput, calculated from wchar read from /proc/<taosd_pid>/io and previous values; unit: byte/s
io_read_disk	DOUBLE		Disk I/O throughput, read from read_bytes from /proc/<taosd_pid>/io; unit: byte/s
io_write_disk	DOUBLE		Disk I/O throughput, read from write_bytes from /proc/<taosd_pid>/io; unit: byte/s
vnodes_num	DOUBLE		Number of vnodes on the dnode
masters	DOUBLE		Number of master nodes on the dnode
has_mnode	DOUBLE		Whether the dnode contains an mnode, value range: contains=1, does not contain=0
has_qnode	DOUBLE		Whether the dnode contains a qnode, value range: contains=1, does not contain=0
has_snode	DOUBLE		Whether the dnode contains an snode, value range: contains=1, does not contain=0
has_bnode	DOUBLE		Whether the dnode contains a bnode, value range: contains=1, does not contain=0
error_log_count	DOUBLE		Total number of errors
info_log_count	DOUBLE		Total number of info messages
debug_log_count	DOUBLE		Total number of debug messages
trace_log_count	DOUBLE		Total number of trace messages
dnode_id	VARCHAR	TAG	dnode id
dnode_ep	VARCHAR	TAG	dnode endpoint
cluster_id	VARCHAR	TAG	cluster id

taosd_dnodes_status Table

The taosd_dnodes_status table records the status information of dnodes.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
status	DOUBLE		dnode status; value range: ready=1, offline=0
dnode_id	VARCHAR	TAG	dnode id
dnode_ep	VARCHAR	TAG	dnode endpoint
cluster_id	VARCHAR	TAG	cluster id

taosd_dnodes_log_dir Table

The taosd_dnodes_log_dir table records log directory information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
avail	DOUBLE		Available space in the log directory; unit: bytes
used	DOUBLE		Used space in the log directory; unit: bytes
total	DOUBLE		Total space in the log directory; unit: bytes
name	VARCHAR	TAG	Log directory name, usually /var/log/taos/
dnode_id	VARCHAR	TAG	dnode id
dnode_ep	VARCHAR	TAG	dnode endpoint
cluster_id	VARCHAR	TAG	cluster id

taosd_dnodes_data_dir Table

The taosd_dnodes_data_dir table records data directory information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
avail	DOUBLE		Available space in the data directory; unit: bytes
used	DOUBLE		Used space in the data directory; unit: bytes
total	DOUBLE		Total space in the data directory; unit: bytes
level	VARCHAR	TAG	Multi-level storage level: 0, 1, 2
name	VARCHAR	TAG	Data directory, usually /var/lib/taos

taosd_mnodes_info Table

The taosd_mnodes_info table records mnode role information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
role	DOUBLE		mnode role; value range: offline = 0, follower = 100, candidate = 101, leader = 102, error = 103, learner = 104
mnode_id	VARCHAR	TAG	master node id
mnode_ep	VARCHAR	TAG	master node endpoint
cluster_id	VARCHAR	TAG	cluster id

taosd_vnodes_role Table

The taosd_vnodes_role table records virtual node role information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
vnode_role	DOUBLE		vnode role; value range: offline = 0, follower = 100, candidate = 101, leader = 102, error = 103, learner = 104
vgroup_id	VARCHAR	TAG	dnode id
dnode_id	VARCHAR	TAG	dnode id
database_name	VARCHAR	TAG	Database name the vgroup belongs to

taosd_sql_req Table

The taosd_sql_req table records server-side SQL request information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
count	DOUBLE		Number of SQL requests
result	VARCHAR	TAG	SQL execution result; value range: Success, Failed
username	VARCHAR	TAG	User name executing the SQL
sql_type	VARCHAR	TAG	SQL type; value range: inserted_rows
dnode_id	VARCHAR	TAG	dnode id
dnode_ep	VARCHAR	TAG	dnode endpoint
vgroup_id	VARCHAR	TAG	vgroup id
cluster_id	VARCHAR	TAG	cluster id

taos_sql_req Table

The taos_sql_req table records client-side SQL request information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
count	DOUBLE		Number of SQL requests
result	VARCHAR	TAG	SQL execution result; value range: Success, Failed
username	VARCHAR	TAG	User name executing the SQL
sql_type	VARCHAR	TAG	SQL type; value range: select, insert, delete
cluster_id	VARCHAR	TAG	cluster id

taos_slow_sql Table

The taos_slow_sql table records client-side slow query information.

field	type	is_tag	comment
_ts	TIMESTAMP		timestamp
count	DOUBLE		Number of SQL requests
result	VARCHAR	TAG	SQL execution result; value range: Success, Failed
username	VARCHAR	TAG	User name executing the SQL
duration	VARCHAR	TAG	SQL execution duration; value range: 3-10s, 10-100s, 100-1000s, 1000s-
cluster_id	VARCHAR	TAG	cluster id

Log Related

TDengine uses log files to record the system's operational status, helping users monitor the system's operation and troubleshoot issues. This section mainly introduces the system logs related to taosc and taosd.

TDengine's log files mainly include ordinary logs and slow logs.

1. Ordinary Log Behavior Explanation
   1. Multiple client processes can run on the same machine, so client log naming follows the format taoslogX.Y, where X is the sequence number (which can be empty or a digit from 0 to 9) and Y is the suffix (0 or 1).
   2. Only one server process can run on the same machine, so server log naming follows the format taosdlog.Y, where Y is the suffix (0 or 1). The rules for determining sequence numbers and suffixes are as follows (assuming the log path is /var/log/taos/):
      1. Determine the sequence number: Use 10 sequence numbers as log naming, from /var/log/taos/taoslog0.Y to /var/log/taos/taoslog9.Y, checking each sequence number to see if it is in use. The first unused sequence number will be used for the log file of that process. If all 10 sequence numbers are in use, the sequence number will be empty, i.e., /var/log/taos/taoslog.Y, and all processes will write to the same file.
      2. Determine the suffix: 0 or 1. For example, if the determined sequence number is 3, the alternative log file names will be /var/log/taos/taoslog3.0 and /var/log/taos/taoslog3.1. If both files do not exist, use suffix 0; if one exists and one does not, use the existing suffix. If both exist, use the one with the most recent modification time.
   3. If the log file exceeds the configured number of lines (numOfLogLines), it will switch suffixes and continue logging. For example, when /var/log/taos/taoslog3.0 is filled, it will switch to /var/log/taos/taoslog3.1 to continue logging. /var/log/taos/taoslog3.0 will be renamed with a timestamp suffix and compressed (asynchronous thread operation).
   4. The parameter logKeepDays controls how many days the log files are retained. For instance, if configured to 1, logs older than one day will be checked and deleted when new logs are compressed. This is not based on natural days.

In addition to recording ordinary logs, SQL statements that exceed the configured execution time will be recorded in the slow logs. Slow log files are primarily used to analyze system performance and troubleshoot performance issues.

2. Slow Log Behavior Explanation
   1. Slow logs will be recorded in the local slow log file and, simultaneously, sent to taosKeeper for structured storage (the monitor switch must be enabled).
   2. Slow log file storage rules are:
      1. A slow log file is generated for each day; if there are no slow logs on that day, there will be no file for that day.
      2. The file name is taosSlowLog.yyyy-mm-dd (e.g., taosSlowLog.2024-08-02), and the log storage path is specified by the logDir configuration.
      3. Logs from multiple clients will be stored in the same taosSlowLog.yyyy-mm-dd file in the specified log path.
      4. Slow log files are not automatically deleted and are not compressed.
      5. They share the same three parameters as ordinary log files: logDir, minimalLogDirGB, and asyncLog. The other two parameters, numOfLogLines and logKeepDays, do not apply to slow logs.