/// <summary>
/// Gets schema from a data table, but parses the data to determine what datatype is best fit.
/// </summary>
/// <param name="outputTableName">The output table name e.g. "CREATE TABLE [NAME] (..."</param>
/// <param name="data">Data to analyze</param>
/// <returns></returns>
public static string FromDataTable_Smart(string outputTableName, DataTable data)
{
var sqlTable = new SqlTableDefinition
{
TableName = outputTableName
};
//loop through each column
for (var colIndex = 0; colIndex < data.Columns.Count; colIndex++)
{
var rowVals = new HashSet <string>(StringComparer.OrdinalIgnoreCase);
//collect row values into hashset
for (var rowIndex = 0; rowIndex < data.Rows.Count; rowIndex++)
{
rowVals.Add(data.Rows[rowIndex][colIndex].ToString());
}
sqlTable.ColumnDefinitions.Add(CreateTableSqlInternal.GetBestFitSqlColumnType(rowVals, data.Columns[colIndex].ColumnName));
}
return(CreateTableSqlInternal.FromSqlTableDefinition(sqlTable));
}
public static string FromDataReader_Smart(string outputTableName, IEnumerable <Func <DataReaderInfo> > dataReaders,
int?numberOfRowsToExamine = null)
{
//maps column names to hashset of unique values present for those columns
var uniqueValList = new ConcurrentDictionary <string, ConcurrentHashSet <string> >();
//we want the field names because these are our output table sql's column names
//this is not thread safe
var masterListOfFieldNames = new ConcurrentHashSet <string>();
//fit the data types from the data readers' data
var result = Parallel.ForEach(dataReaders, new ParallelOptions {
MaxDegreeOfParallelism = 12
},
dataReaderInfoFac =>
{
//get column names and setup hash dictionaries
var numRows = 0;
var drInfo = dataReaderInfoFac();
using var dataReader = drInfo.DataReader;
var readerFieldNames = dataReader.GetFieldNames();
//if there was a problem we may have to read to read first to initialize in order to get fields
var tryAgain = (readerFieldNames == null) || (readerFieldNames.Length == 0);
if (tryAgain)
{
dataReader.Read();
readerFieldNames = dataReader.GetFieldNames();
numRows++;
}
if ((readerFieldNames == null) || (readerFieldNames.Length == 0))
{
throw new Exception($"Could not get field names for file {drInfo.FilePath}");
}
//unfortunately this duplicated code is here for a reason.. we want to read to initialize the reader, but we also want to capture the first row if we already read. Please refactor though
foreach (var readerFieldName in readerFieldNames)
{
if (!uniqueValList.ContainsKey(readerFieldName))
{
uniqueValList.AddOrUpdate(
readerFieldName, //our key for the dictionary
new ConcurrentHashSet <string>(),
//if it doesn't exist create a new concurrent dictionary
(field, uniqueVals) => //otherwise we want to return the new updated value
uniqueVals);
}
;
if (masterListOfFieldNames.Contains(readerFieldName) == false)
{
masterListOfFieldNames.Add(readerFieldName);
}
}
//we tried again and got the field names so we can go ahead and add the values that are currently on record
if (tryAgain)
{
foreach (var col in readerFieldNames)
{
var val = dataReader[col]?.ToString();
var uvl = uniqueValList[col];
uvl.Add(val);
}
}
//collect unique row values by column
while (dataReader.Read() && ((numRows < numberOfRowsToExamine) || (numberOfRowsToExamine == null)))
{
foreach (var col in readerFieldNames)
{
var val = dataReader[col]?.ToString();
var uvl = uniqueValList[col];
uvl.Add(val);
}
numRows++;
}
});
var sqlTable = new SqlTableDefinition
{
TableName = outputTableName
};
foreach (var col in masterListOfFieldNames.ToArray())
{
sqlTable.ColumnDefinitions.Add(CreateTableSqlInternal.GetBestFitSqlColumnType(uniqueValList[col].Hashset, col));
}
return(CreateTableSqlInternal.FromSqlTableDefinition(sqlTable));
}
