/// <summary>
/// Retrieves the columns for a given view.
/// </summary>
/// <param name="pragma">A schema-specific pragma accessor.</param>
/// <param name="viewName">A view name.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>An ordered collection of columns.</returns>
/// <exception cref="ArgumentNullException"><paramref name="viewName"/> is <c>null</c>.</exception>
protected virtual Task <IReadOnlyList <IDatabaseColumn> > LoadColumnsAsync(ISqliteDatabasePragma pragma, Identifier viewName, CancellationToken cancellationToken)
{
if (pragma == null)
{
throw new ArgumentNullException(nameof(pragma));
}
if (viewName == null)
{
throw new ArgumentNullException(nameof(viewName));
}
return(LoadColumnsAsyncCore(pragma, viewName, cancellationToken));
}
private async Task <IReadOnlyList <IDatabaseColumn> > LoadColumnsAsyncCore(ISqliteDatabasePragma pragma, Identifier viewName, CancellationToken cancellationToken)
{
IEnumerable <Pragma.Query.pragma_table_info> tableInfos;
try
{
// When the view is invalid, this may throw an exception so we catch it.
// This does mean that we are in a partial state, but if the definition is corrected
// and the view is queried again then we'll end up with something correct.
tableInfos = await pragma.TableInfoAsync(viewName, cancellationToken).ConfigureAwait(false);
}
catch (SqliteException ex) when(ex.SqliteErrorCode == SqliteError)
{
return(Array.Empty <IDatabaseColumn>());
}
if (tableInfos.Empty())
{
return(Array.Empty <IDatabaseColumn>());
}
var result = new List <IDatabaseColumn>();
foreach (var tableInfo in tableInfos)
{
if (tableInfo.name == null)
{
continue;
}
var columnName = tableInfo.name;
var columnTypeName = tableInfo.type;
if (columnTypeName.IsNullOrWhiteSpace())
{
columnTypeName = await GetTypeofColumnAsync(viewName, columnName, cancellationToken).ConfigureAwait(false);
}
var affinity = AffinityParser.ParseTypeName(columnTypeName);
var columnType = new SqliteColumnType(affinity);
var defaultValue = !tableInfo.dflt_value.IsNullOrWhiteSpace()
? Option <string> .Some(tableInfo.dflt_value)
: Option <string> .None;
var column = new DatabaseColumn(columnName, columnType, !tableInfo.notnull, defaultValue, Option <IAutoIncrement> .None);
result.Add(column);
}
return(result);
}
