public static List <T> BulkSelect <T, TKey>(
this IQueryable <T> source,
Expression <Func <T, TKey> > keyExpression,
IEnumerable <TKey> keyData)
{
EnsureNoNavigationProperties(keyExpression);
BulkSelectInterceptor.StartInterception();
var keyDataTable = $"_schema_{DateTime.Now.Ticks}";
var schemaQuery = source.Select(keyExpression);
var schemaSql = $"CREATE TEMP TABLE {keyDataTable} ON COMMIT DROP AS ({schemaQuery} LIMIT 0)";
var context = NpgsqlHelper.GetContextFromQuery(source);
var conn = NpgsqlHelper.GetNpgsqlConnection(context);
var localTr = NpgsqlHelper.EnsureOrStartTransaction(context);
try
{
context.Database.ExecuteSqlCommand(schemaSql);
var columnsInfo = NpgsqlHelper.GetColumnsInfo(context, keyDataTable);
var propsMap = GetPropertiesMap(
((IObjectContextAdapter)context).ObjectContext,
schemaQuery.Expression,
typeof(TKey));
var mapsInfo = new List <MappingInfo>();
foreach (var propMap in propsMap)
{
var cinfo = columnsInfo[propMap.Item2];
mapsInfo.Add(new MappingInfo()
{
Property = propMap.Item1,
ColumnInfo = cinfo,
NpgsqlType = NpgsqlBulkUploader.GetNpgsqlType(cinfo)
});
}
var columnsCsv = string.Join(", ",
mapsInfo.Select(x => NpgsqlHelper.GetQualifiedName(x.ColumnInfo.ColumnName)));
var copySql = $"COPY {keyDataTable} ({columnsCsv}) FROM STDIN (FORMAT BINARY)";
using (var importer = conn.BeginBinaryImport(copySql))
{
foreach (var kd in keyData)
{
importer.StartRow();
foreach (var kp in mapsInfo)
{
importer.Write(kp.Property.GetValue(kd), kp.NpgsqlType);
}
}
}
var whereSql = string.Join(" AND ",
mapsInfo.Select(x => $"source.{NpgsqlHelper.GetQualifiedName(x.ColumnInfo.ColumnName)}" +
$" = {keyDataTable}.{NpgsqlHelper.GetQualifiedName(x.ColumnInfo.ColumnName)}"));
var selectSql = $"SELECT source.* FROM ({source}) as source\n" +
$"JOIN {keyDataTable} ON {whereSql}";
BulkSelectInterceptor.SetReplaceQuery(source.ToString(), selectSql);
var result = source.ToList();
localTr?.Commit();
return(result);
}
catch
{
localTr?.Rollback();
throw;
}
finally
{
BulkSelectInterceptor.StopInterception();
}
}
