/// <summary>
/// Drops an existing identity on the column
/// </summary>
/// <param name="expression"></param>
/// <param name="ifExists">If true and the column is not an identity column, no error is thrown. In this case a notice is issued instead.</param>
/// <returns>The next step</returns>
/// <remarks>Deliberate choice to extend IAlterColumnOptionSyntax rather than IColumnOptionSyntax<TNext, TNextFk>
/// in order to prevent using these methods when adding a column to the table, since it makes no sense. It does mean
/// the syntax migration.Alter.Table("tableName").AlterColumn("columnName") cannot be used since no distinction is made
/// between the the return types of AddColumn or AlterColumn on the IAlterTableColumnAsTypeSyntax interface which is inconvenient
/// but helps prevent misuse.
/// </remarks>
public static IAlterColumnOptionSyntax DropIdentity(this IAlterColumnOptionSyntax expression, bool ifExists)
=> SetIdentity(expression, null, ifExists ? PostgresIdentityModificationType.DropIfExists : PostgresIdentityModificationType.Drop, GetColumn(expression));
/// <summary>
/// Alters the strategy for an existing generated identity on the column
/// </summary>
/// <param name="expression"></param>
/// <param name="generation"></param>
/// <returns>The next step</returns>
/// <remarks>Deliberate choice to extend IAlterColumnOptionSyntax rather than IColumnOptionSyntax<TNext, TNextFk>
/// in order to prevent using these methods when adding a column to the table, since it makes no sense. It does mean
/// the syntax migration.Alter.Table("tableName").AlterColumn("columnName") cannot be used since no distinction is made
/// between the the return types of AddColumn or AlterColumn on the IAlterTableColumnAsTypeSyntax interface which is inconvenient
/// but helps prevent misuse.
/// </remarks>
public static IAlterColumnOptionSyntax SetIdentity(this IAlterColumnOptionSyntax expression, PostgresGenerationType generation)
=> SetIdentity(expression, generation, PostgresIdentityModificationType.Set, GetColumn(expression));
