s_mysql_mysql_stmt_metadata Struct Reference

A service that provides the API to get information about statement metadata including the number of the parameters in a prepared statement and their metatdata. More...

#include <mysql_statement_service.h>

Public Attributes
mysql_service_status_t(*	param_count )(my_h_statement statement, uint32_t *parameter_count)
	Get the number of parameters in the prepared statement. More...
mysql_service_status_t(*	param_metadata )(my_h_statement statement, uint32_t index, const char *metadata, void *data)
	Get the metadata of a parameter in a prepared statement. More...

Detailed Description

A service that provides the API to get information about statement metadata including the number of the parameters in a prepared statement and their metatdata.

For prepared statement, to get the number of parameters uint64_t num_parameters; SERVICE_PLACEHOLDER(mysql_stmt_metadata)->param_count(statement, &num_parameters)

Member Data Documentation

param_count

mysql_service_status_t(* s_mysql_mysql_stmt_metadata::param_count) (my_h_statement statement, uint32_t *parameter_count)

Get the number of parameters in the prepared statement.

Note

Calling this on regular statements would fail.

Parameters

[in]	statement	A handle to the statement
[out]	parameter_count	The number of parameters

Returns

Status of the performed operation

Return values

false	success
true	failure

param_metadata

mysql_service_status_t(* s_mysql_mysql_stmt_metadata::param_metadata) (my_h_statement statement, uint32_t index, const char *metadata, void *data)

Get the metadata of a parameter in a prepared statement.

The metadata specifies whether the parameter can be null, the type of the parameter, whether the value is signed.

For example, in this query, "SELECT * FROM table WHERE col = ?", we need to know the parameter specified by '?' is null or not, its type, and if it is integer, whether it is signed. MySQL will provide this information and this function is to get these info.

auto is_nullable = bool{}; if (SERVICE_PLACEHOLDER(mysql_stmt_metadata) ->param_metadata(statement, index, "null_bit", &is_nullable)) return {}; auto sql_type = Sql_type{}; if (SERVICE_PLACEHOLDER(mysql_stmt_metadata) ->param_metadata(statement, index, "type", &sql_type)) return {}; auto is_unsigned = bool{}; if (SERVICE_PLACEHOLDER(mysql_stmt_metadata) ->param_metadata(statement, index, "is_unsigned", &is_unsigned)) return {}; auto charset = static_cast<char const *>(nullptr); if (SERVICE_PLACEHOLDER(mysql_stmt_metadata) ->param_metadata(statement, index, "charset", &charset)) return {};

Note

Calling this on regular statements would fail.

Parameters

[in]	statement	A handle to the statement
[in]	index	0-based index of the parameter
[in]	metadata	The metadata argument is the attribute that you want to get

The following attributes are supported:

• Parameter is null ("null_bit" of the returned bool type)
• Parameter type ("type" of the returned uint64_t type)
• Parameter is unsigned ("is_unsigned" of the returned bool type)
• Parameter charset ("charset" of the returned const char* type)
• Parameter max_byte_length ("max_byte_length" of the returned size_t type)

Parameters

[out]

data

The data argument is the value for the member

Returns

Status of the performed operation

Return values

false	success
true	failure

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The documentation for this struct was generated from the following file:

• include/mysql/components/services/mysql_statement_service.h