◆ SQT_INDEX

#define SQT_INDEX ( ... )

Defines an index with auto-generated names based on the specified columns.

Parameters

...	The names of the columns that form the index. An index can consist of up to 8 columns.

This macro must be used between the SQT_TABLE_BEGIN and SQT_TABLE_END macros and must be placed after all definitions of the columns that are part of the index. There can be multiple index definitions in a table type.

The index name in the database is generated using the following format:

SQTIndex_<TableName>_<Column1>_<Column2>_...

Example usage:

struct MyEntity {
    int id{};
    std::string name;
};
 
SQT_TABLE_BEGIN(MyEntityTable, MyEntity)
SQT_COLUMN_FIELD(ID, id)
SQT_COLUMN_FIELD(Name, name)
// Define an index with the ID and Name columns.
SQT_INDEX(ID, Name)
SQT_TABLE_END

The following code demonstrates the generated definition of the index in the table type:

class TableType {
public:
    // Column types.
    class IDType;
    class NameType;
 
    // The class for the index type, whose name is generated by joining the column names with 
    // an underscore ('_') as the delimiter and appending the result to the prefix 
    // "IndexType_".
    class IndexType_ID_Name :
        public sqt::CompositeColumn<IDType, NameType>,
        public sqt::AbstractIndex {
 
    public:
        //Forbids copying.
        IndexType_IDName(const IndexType_IDName&) = delete;
        IndexType_IDName& operator=(const IndexType_IDName&) = delete;
 
        //Forbids moving.
        IndexType_IDName(IndexType_IDName&&) = delete;
        IndexType_IDName& operator=(IndexType_IDName&&) = delete;
 
        // Assignment operator that generates an assignment expression.
        constexpr auto operator=(const ValueType&) const noexcept;
 
        // Ordering operator that generates an ordering term expression.
        constexpr auto Asc() const noexcept;
        constexpr auto Desc() const noexcept;
 
        // Comparison operators that generate predicate expressions.
        // Here shows only the == operator. Other operators (!=, <, <=, >, >=) are omitted.
        friend constexpr auto operator==(const IndexType_IDName&, const ValueType&) const noexcept;
        friend constexpr auto operator==(const IndexType_IDName&, sqt::Placeholder) const noexcept;
        friend constexpr auto operator==(const ValueType&, const IndexType_IDName&) const noexcept;
        friend constexpr auto operator==(sqt::Placeholder, const IndexType_IDName&) const noexcept;
    };
 
    // The instance of the index, which is defined as a public member variable of the table
    // type. The name of the variable is generated by joining the column names with an 
    // underscore ('_') as the delimiter and appending the result to the prefix "Index_".
    IndexType_ID_Name Index_ID_Name;
};

The following alternative macros can also be used to define indexes:

SQT_INDEX_2: Defines an index with custom names.
SQT_INDEX_UNIQUE: Defines an unique index with auto-generated names.
SQT_INDEX_UNIQUE_2: Defines an unique index with custom names.

See also: sqt::AbstractIndex; sqt::CompositeColumn<>; SQT_INDEX_2; SQT_INDEX_UNIQUE; SQT_INDEX_UNIQUE_2; SQT_TABLE_BEGIN

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