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Compatibility and Use Limits

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最終更新日: 2026-07-10 11:13:51

This document describes the usage limitations and compatibility specifications for TDSQL Boundless read-only analysis instances.
Note:
 Except for the supported scenarios mentioned in this document, the read-only analysis instance does not support any other special scenarios.
Architecture and Availability Features
A read-only analysis instance in a single-node deployment does not have high availability. A node failure will cause the read-only analysis instance to become unavailable. To ensure the read-only analysis instance continues to provide services, purchase a multi-node deployment.
Syntax Limits
The read-only analysis instance supports only read-only query statements and does not support any data modification operations, including DDL and DML. The specific limitations are as follows:
Only SELECT query statements are supported. A small number of keywords and syntax within SELECT statements are not supported. For details, see SELECT Statement Description.
CTE syntax and window functions are supported. There are some limitations when CTE syntax and window functions are used. For details, see CTE Syntax Usage Instructions and Window Function Use Instructions.
Full-text search syntax is not supported.
Custom functions and stored procedures are not supported.
After a read-only analysis instance is enabled for TDSQL Boundless, performing certain data modification operations on the read-write instance may cause abnormal data loading in the read-only analysis instance. For details, see Data Loading Limits.
Table Quantity Limits
The recommended maximum number of tables in a read-only analysis instance is 20,000.
The read-only analysis instance has limited support for partition tables in terms of scope and scenarios. For details, see Data Loading Limits.
The read-only analysis instance has limited support for data types. If a table contains unsupported data types, it cannot be loaded into the read-only analysis instance. For details, see Data Types.
Column Value Size Limits
The size limit for ordinary column values in a read-only analysis instance is 16 MB by default. If a table contains column values exceeding 16 MB, an error will be reported and the loading process will be suspended when you attempt to load it into the read-only analysis instance.
SQL Mode
The read-only analysis instance supports setting the SQL Mode at the global or session level using the SET [ SESSION | GLOBAL ] sql_mode='modes' statement. It also supports querying the current SQL Mode using SELECT @@sql_mode.
The common MySQL system SQL Modes supported by the read-only analysis instance are listed in the table below. SQL Modes not listed are not supported. Note that some SQL Modes are not applicable in the read-only analysis instance, such as NO_AUTO_CREATE_USER and NO_ENGINE_SUBSTITUTION.
Term
Description
PIPES_AS_CONCAT
Treats || as the string concatenation operator (+) (same as CONCAT()), not as OR.
ANSI_QUOTES
Treats " as an identifier. After ANSI_QUOTES is enabled, only the content within single quotes is treated as a string literal, and double quotes are interpreted as identifiers. Therefore, you cannot use double quotes to quote strings.
IGNORE_SPACE
When this mode is enabled, the system ignores spaces. For example, user and user are treated as the same.
ONLY_FULL_GROUP_BY
If a column that is not processed by an aggregate function or not included in GROUP BY appears in SELECT, HAVING, or ORDER BY, the SQL statement is invalid.
NO_UNSIGNED_SUBTRACTION
In subtraction, if an operand has no sign, the result is not marked as UNSIGNED.
NO_BACKSLASH_ESCAPES
When this mode is enabled, the backslash symbol \\ represents only itself.
STRICT_TRANS_TABLES
Enables strict mode for transactional storage engines and rolls back the entire statement after an invalid value is inserted.
STRICT_ALL_TABLES
For transactional tables, rolls back the entire transaction statement after an invalid value is written.
NO_ZERO_IN_DATE
In strict mode, dates with a month or day part of 0 are not accepted. If the IGNORE option is used, such dates are inserted as 0000-00-00. In non-strict mode, the date is accepted, but a warning is generated.
NO_ZERO_DATE
In strict mode, 0000-00-00 is not treated as a valid date. You can still use the IGNORE option to insert a zero date. In non-strict mode, the date is accepted, but a warning is generated.
ALLOW_INVALID_DATES
Does not check the validity of the entire date, but only checks whether the month value is between 1 and 12 and whether the day value is between 1 and 31. Applies only to DATE and DATETIME columns. TIMESTAMP columns require a full validity check.
ERROR_FOR_DIVISION_BY_ZERO
When this mode is enabled, the system generates an error if the divisor is 0 during an INSERT or UPDATE operation. When this mode is not enabled, the system generates a warning and replaces the result with NULL if the divisor is 0.
REAL_AS_FLOAT
Treats REAL as a synonym for FLOAT, not for DOUBLE.
NO_DIR_IN_CREATE
Ignores all INDEX DIRECTORY and DATA DIRECTORY directives when a table is created. This option is useful only for replication servers.
NO_AUTO_CREATE_USER
Prevents GRANT from automatically creating new users (except when a password is specified). Has no practical effect in a read-only analysis instance.
NO_ENGINE_SUBSTITUTION
Prevents the storage engine from being automatically substituted when the required storage engine is disabled or not compiled. Has no practical effect in a read-only analysis instance.
Character Set and Collation
A character set is a collection of symbols and encodings. The default character set in a read-only analysis instance is utf8mb4.
A collation is a rule for comparing characters and defining character sorting order within a character set. For example, under a binary collation, 'A' and 'a' are not considered equal (the comparison is case-sensitive).
The character sets and collations supported by the read-only analysis instance are shown in the table below.
Character Set
Description
Supported Collation
Maximum Bytes
utf8
UTF-8 Unicode
utf8_bin,utf8_general_ci,utf8_unicode_ci
3
utf8mb4
UTF-8 Unicode
utf8mb4_bin,utf8mb4_general_ci,utf8mb4_unicode_ci,utf8mb4_0900_ai_ci,utf8mb4_0900_bin
4
Attention:
When objects in the read-write instance use a different character set, loading data into the read-only analysis instance is not affected. However, some special characters may behave abnormally when queried in the read-only analysis instance. Additionally, sorting results may be inconsistent due to collation differences.
Other Behavior Descriptions
The read-only analysis instance executes SELECT ... GROUP BY expr queries, and the returned results are consistent with those in MySQL 8.0. By default, the results are not sorted.

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Term	Description
PIPES_AS_CONCAT	Treats `\|\|` as the string concatenation operator (+) (same as `CONCAT()`), not as OR.
ANSI_QUOTES	Treats `"` as an identifier. After ANSI_QUOTES is enabled, only the content within single quotes is treated as a string literal, and double quotes are interpreted as identifiers. Therefore, you cannot use double quotes to quote strings.
IGNORE_SPACE	When this mode is enabled, the system ignores spaces. For example, user and user are treated as the same.
ONLY_FULL_GROUP_BY	If a column that is not processed by an aggregate function or not included in `GROUP BY` appears in `SELECT`, `HAVING`, or `ORDER BY`, the SQL statement is invalid.
NO_UNSIGNED_SUBTRACTION	In subtraction, if an operand has no sign, the result is not marked as UNSIGNED.
NO_BACKSLASH_ESCAPES	When this mode is enabled, the backslash symbol `\\` represents only itself.
STRICT_TRANS_TABLES	Enables strict mode for transactional storage engines and rolls back the entire statement after an invalid value is inserted.
STRICT_ALL_TABLES	For transactional tables, rolls back the entire transaction statement after an invalid value is written.
NO_ZERO_IN_DATE	In strict mode, dates with a month or day part of 0 are not accepted. If the IGNORE option is used, such dates are inserted as `0000-00-00`. In non-strict mode, the date is accepted, but a warning is generated.
NO_ZERO_DATE	In strict mode, `0000-00-00` is not treated as a valid date. You can still use the IGNORE option to insert a zero date. In non-strict mode, the date is accepted, but a warning is generated.
ALLOW_INVALID_DATES	Does not check the validity of the entire date, but only checks whether the month value is between 1 and 12 and whether the day value is between 1 and 31. Applies only to `DATE` and `DATETIME` columns. `TIMESTAMP` columns require a full validity check.
ERROR_FOR_DIVISION_BY_ZERO	When this mode is enabled, the system generates an error if the divisor is 0 during an `INSERT` or `UPDATE` operation. When this mode is not enabled, the system generates a warning and replaces the result with `NULL` if the divisor is 0.
REAL_AS_FLOAT	Treats `REAL` as a synonym for `FLOAT`, not for `DOUBLE`.
NO_DIR_IN_CREATE	Ignores all `INDEX DIRECTORY` and `DATA DIRECTORY` directives when a table is created. This option is useful only for replication servers.
NO_AUTO_CREATE_USER	Prevents GRANT from automatically creating new users (except when a password is specified). Has no practical effect in a read-only analysis instance.
NO_ENGINE_SUBSTITUTION	Prevents the storage engine from being automatically substituted when the required storage engine is disabled or not compiled. Has no practical effect in a read-only analysis instance.

Character Set	Description	Supported Collation	Maximum Bytes
utf8	UTF-8 Unicode	utf8_bin,utf8_general_ci,utf8_unicode_ci	3
utf8mb4	UTF-8 Unicode	utf8mb4_bin,utf8mb4_general_ci,utf8mb4_unicode_ci,utf8mb4_0900_ai_ci,utf8mb4_0900_bin	4

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TDSQL Boundless

Compatibility and Use Limits

Architecture and Availability Features

Syntax Limits

Table Quantity Limits

Column Value Size Limits

SQL Mode

Character Set and Collation

Other Behavior Descriptions

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