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Description

MariaDB Error 1390 indicates that a prepared SQL statement contains more placeholders (parameters) than allowed by the server's configuration. This typically occurs when an application constructs a complex query with a very large number of dynamic values, such as extensive `IN` clauses or `VALUES` lists.

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Error Message

Prepared statement contains too many placeholders

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Known Causes

4 known causes

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Exceeding Default Parameter Limit

MariaDB has a default internal limit on the number of parameters a single prepared statement can contain, which has been surpassed.

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Large Dynamically Generated Queries

Application code or ORMs generating SQL statements with a huge number of dynamic values, for instance, in bulk inserts or complex filtering, can inadvertently create too many placeholders.

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Inefficient ORM Query Generation

Certain Object-Relational Mappers (ORMs) or database frameworks might generate inefficient SQL queries with an excessive number of parameters for specific data operations.

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Application Logic Error

A bug in the application's logic could lead to an unintended proliferation of parameters when constructing prepared statements, especially when processing large collections of data.

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Solutions

3 solutions available

1. Reduce the Number of Placeholders in the Statement easy

Break down the large prepared statement into smaller, more manageable ones.

1

Analyze the prepared statement that is causing the error. Identify if there are specific parts that can be logically separated or if the statement is trying to insert/update/delete a very large number of rows in a single operation.

2

If the statement is performing a bulk operation (e.g., inserting many rows), split it into multiple smaller prepared statements. For instance, instead of inserting 1000 rows with one statement, use 10 statements to insert 100 rows each.

Example of splitting a large INSERT statement:
-- Original (problematic)
PREPARE stmt FROM 'INSERT INTO my_table (col1, col2) VALUES (?, ?), (?, ?), ... (?, ?)'; -- 1000 placeholders
EXECUTE stmt USING val1, val2, val3, val4, ...;

-- Split into smaller statements
PREPARE stmt1 FROM 'INSERT INTO my_table (col1, col2) VALUES (?, ?)';
EXECUTE stmt1 USING val1, val2;

PREPARE stmt2 FROM 'INSERT INTO my_table (col1, col2) VALUES (?, ?)';
EXECUTE stmt2 USING val3, val4;
-- ... and so on for smaller batches

3

If the statement is complex with many conditions, consider rewriting it to be more concise or breaking it into multiple, simpler statements that achieve the same result.

2. Optimize Query Logic for Fewer Parameters medium

Refactor the query to use fewer placeholders by leveraging MariaDB features.

1

Examine the query for repetitive conditions or opportunities to use set-based operations instead of row-by-row processing with many placeholders.

2

If the statement involves checking against a list of values, consider using `IN` clauses or joining with a temporary table or derived table instead of using multiple `OR` conditions with placeholders.

Example: Replacing multiple OR conditions with IN
-- Original (problematic)
PREPARE stmt FROM 'SELECT * FROM my_table WHERE col1 = ? OR col1 = ? OR col1 = ? OR ...'; -- many placeholders
EXECUTE stmt USING val1, val2, val3, ...;

-- Refactored using IN
PREPARE stmt FROM 'SELECT * FROM my_table WHERE col1 IN (?, ?, ?)'; -- fewer placeholders
EXECUTE stmt USING val1, val2, val3;

-- Or even better, if the list is static or can be generated programmatically:
PREPARE stmt FROM 'SELECT * FROM my_table WHERE col1 IN (SELECT value FROM temp_values_table)'; -- no placeholders for values
EXECUTE stmt;

3

For bulk updates or inserts, investigate if MariaDB's `LOAD DATA INFILE` or `INSERT ... SELECT` statements can be used, as these often handle large datasets more efficiently and with fewer explicit placeholders in the prepared statement itself (though the underlying data loading might still involve placeholders in the client code).

3. Increase the `max_prepared_stmt_count` (with caution) advanced

Adjust the server configuration to allow more prepared statements, but understand the implications.

1

Understand that this is a server-wide configuration and increasing it might have performance implications or mask underlying issues with query design. It's generally preferable to optimize the query.

2

Locate your MariaDB configuration file (e.g., `my.cnf` or `my.ini`).

3

Add or modify the `max_prepared_stmt_count` parameter in the `[mysqld]` section of your configuration file. The default is typically 16384. You might need to increase it significantly, but monitor memory usage.

[mysqld]
max_prepared_stmt_count = 32768  # Example: Doubling the default

4

Restart the MariaDB server for the changes to take effect.

For systemd-based systems:
sudo systemctl restart mariadb

For init.d-based systems:
sudo service mariadb restart

5

Monitor server memory usage and performance after making this change. If you see significant increases in memory consumption or performance degradation, this might not be the right solution.

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Related Errors

5 related errors

MariaDB Error 1390: Exceeding Parameter Limit