305 lines
10 KiB
C++
305 lines
10 KiB
C++
//
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// Copyright (c) 2019-2024 Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef BOOST_MYSQL_METADATA_HPP
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#define BOOST_MYSQL_METADATA_HPP
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#include <boost/mysql/column_type.hpp>
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#include <boost/mysql/string_view.hpp>
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#include <boost/mysql/detail/access.hpp>
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#include <boost/mysql/detail/coldef_view.hpp>
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#include <boost/mysql/detail/flags.hpp>
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#include <string>
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namespace boost {
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namespace mysql {
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/**
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* \brief Metadata about a column in a SQL query.
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* \details This is a regular, value type. Instances of this class are not created by the user
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* directly, but by the library.
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*/
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class metadata
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{
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public:
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/**
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* \brief Default constructor.
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* \details The constructed metadata object has undefined
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* values for all of its members.
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*
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* \par Exception safety
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* No-throw guarantee.
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*/
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metadata() = default;
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/**
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* \brief Move constructor.
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*
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* \par Exception safety
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* No-throw guarantee.
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*
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* \par Object lifetimes
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* `string_view`s obtained by calling accessor functions on `other` are invalidated.
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*/
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metadata(metadata&& other) = default;
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/**
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* \brief Copy constructor.
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*
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* \par Exception safety
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* Strong guarantee. Internal allocations may throw.
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*/
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metadata(const metadata& other) = default;
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/**
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* \brief Move assignment.
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*
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* \par Exception safety
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* No-throw guarantee.
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*
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* \par Object lifetimes
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* `string_view`s obtained by calling accessor functions on both `*this` and `other`
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* are invalidated.
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*/
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metadata& operator=(metadata&& other) = default;
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/**
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* \brief Copy assignment.
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*
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* \par Exception safety
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* Basic guarantee. Internal allocations may throw.
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*
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* \par Object lifetimes
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* `string_view`s obtained by calling accessor functions on `*this`
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* are invalidated.
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*/
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metadata& operator=(const metadata& other) = default;
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/// Destructor.
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~metadata() = default;
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/**
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* \brief Returns the name of the database (schema) the column belongs to.
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* \details
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* This is optional information - it won't be populated unless
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* the connection executing the query has `meta_mode() == metadata_mode::full`.
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*
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* \par Exception safety
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* No-throw guarantee.
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*
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* \par Object lifetimes
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* The returned reference is valid as long as `*this` is alive and hasn't been
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* assigned to or moved from.
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*/
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string_view database() const noexcept { return schema_; }
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/**
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* \brief Returns the name of the virtual table the column belongs to.
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* \details If the table was aliased, this will be the name of the alias
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* (e.g. in `"SELECT * FROM employees emp"`, `table()` will be `"emp"`).
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*\n
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* This is optional information - it won't be populated unless
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* the connection executing the query has `meta_mode() == metadata_mode::full`.
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*
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* \par Exception safety
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* No-throw guarantee.
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*
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* \par Object lifetimes
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* The returned reference is valid as long as `*this` is alive and hasn't been
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* assigned to or moved from.
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*/
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string_view table() const noexcept { return table_; }
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/**
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* \brief Returns the name of the physical table the column belongs to.
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* \details E.g. in `"SELECT * FROM employees emp"`,
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* `original_table()` will be `"employees"`.
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* \n
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* This is optional information - it won't be populated unless
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* the connection executing the query has `meta_mode() == metadata_mode::full`.
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*
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* \par Exception safety
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* No-throw guarantee.
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*
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* \par Object lifetimes
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* The returned reference is valid as long as `*this` is alive and hasn't been
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* assigned to or moved from.
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*/
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string_view original_table() const noexcept { return org_table_; }
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/**
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* \brief Returns the actual name of the column.
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* \details If the column was aliased, this will be the name of the alias
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* (e.g. in `"SELECT id AS employee_id FROM employees"`,
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* `column_name()` will be `"employee_id"`).
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*\n
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* This is optional information - it won't be populated unless
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* the connection executing the query has `meta_mode() == metadata_mode::full`.
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*
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* \par Exception safety
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* No-throw guarantee.
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*
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* \par Object lifetimes
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* The returned reference is valid as long as `*this` is alive and hasn't been
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* assigned to or moved from.
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*/
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string_view column_name() const noexcept { return name_; }
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/**
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* \brief Returns the original (physical) name of the column.
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* \details E.g. in `"SELECT id AS employee_id FROM employees"`,
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* `original_column_name()` will be `"id"`.
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* \n
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* This is optional information - it won't be populated unless
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* the connection executing the query has `meta_mode() == metadata_mode::full`.
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*
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* \par Exception safety
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* No-throw guarantee.
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*
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* \par Object lifetimes
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* The returned reference is valid as long as `*this` is alive and hasn't been
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* assigned to or moved from.
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*/
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string_view original_column_name() const noexcept { return org_name_; }
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/**
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* \brief Returns the ID of the collation that fields belonging to this column use.
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* \details This is <b>not</b> the collation used when defining the column
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* in a `CREATE TABLE` statement, but the collation that fields that belong to
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* this column and are sent to the client have. It usually matches the connection's collation.
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*
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* \par Exception safety
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* No-throw guarantee.
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*/
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std::uint16_t column_collation() const noexcept { return character_set_; }
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/**
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* \brief Returns the maximum length of the column.
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* \par Exception safety
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* No-throw guarantee.
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*/
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unsigned column_length() const noexcept { return column_length_; }
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/**
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* \brief Returns the type of the column (see \ref column_type for more info).
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* \par Exception safety
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* No-throw guarantee.
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*/
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column_type type() const noexcept { return type_; }
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/**
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* \brief Returns the number of decimals of the column.
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* \par Exception safety
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* No-throw guarantee.
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*/
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unsigned decimals() const noexcept { return decimals_; }
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/**
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* \brief Returns `true` if the column is not allowed to be NULL, `false` if it is nullable.
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_not_null() const noexcept { return flag_set(detail::column_flags::not_null); }
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/**
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* \brief Returns `true` if the column is part of a `PRIMARY KEY`.
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_primary_key() const noexcept { return flag_set(detail::column_flags::pri_key); }
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/**
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* \brief Returns `true` if the column is part of a `UNIQUE KEY` (but not a `PRIMARY KEY`).
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_unique_key() const noexcept { return flag_set(detail::column_flags::unique_key); }
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/**
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* \brief Returns `true` if the column is part of a `KEY` (but not a `UNIQUE KEY` or `PRIMARY KEY`).
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_multiple_key() const noexcept { return flag_set(detail::column_flags::multiple_key); }
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/**
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* \brief Returns `true` if the column has no sign (is `UNSIGNED`).
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_unsigned() const noexcept { return flag_set(detail::column_flags::unsigned_); }
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/**
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* \brief Returns `true` if the column is defined as `ZEROFILL` (padded to its maximum length by
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* zeros).
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_zerofill() const noexcept { return flag_set(detail::column_flags::zerofill); }
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/**
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* \brief Returns `true` if the column is defined as `AUTO_INCREMENT`.
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_auto_increment() const noexcept { return flag_set(detail::column_flags::auto_increment); }
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/**
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* \brief Returns `true` if the column does not have a default value.
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool has_no_default_value() const noexcept { return flag_set(detail::column_flags::no_default_value); }
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/**
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* \brief Returns `true` if the column is defined as `ON UPDATE CURRENT_TIMESTAMP`.
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* \par Exception safety
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* No-throw guarantee.
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*/
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bool is_set_to_now_on_update() const noexcept { return flag_set(detail::column_flags::on_update_now); }
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private:
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std::string schema_;
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std::string table_; // virtual table
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std::string org_table_; // physical table
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std::string name_; // virtual column name
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std::string org_name_; // physical column name
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std::uint16_t character_set_;
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std::uint32_t column_length_; // maximum length of the field
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column_type type_; // type of the column
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std::uint16_t flags_; // Flags as defined in Column Definition Flags
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std::uint8_t decimals_; // max shown decimal digits. 0x00 for int/static strings; 0x1f for
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// dynamic strings, double, float
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metadata(const detail::coldef_view& coldef, bool copy_strings)
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: schema_(copy_strings ? coldef.database : string_view()),
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table_(copy_strings ? coldef.table : string_view()),
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org_table_(copy_strings ? coldef.org_table : string_view()),
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name_(copy_strings ? coldef.name : string_view()),
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org_name_(copy_strings ? coldef.org_name : string_view()),
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character_set_(coldef.collation_id),
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column_length_(coldef.column_length),
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type_(coldef.type),
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flags_(coldef.flags),
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decimals_(coldef.decimals)
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{
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}
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bool flag_set(std::uint16_t flag) const noexcept { return flags_ & flag; }
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#ifndef BOOST_MYSQL_DOXYGEN
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friend struct detail::access;
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#endif
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};
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} // namespace mysql
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} // namespace boost
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#endif
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