/// <summary>
/// Creates random list of columns from the given source collection. The rules are:
/// * table cannot contain more than 1024 non-sparse columns
/// * total row size of non-sparse columns should not exceed 8060 or 8018 (with sparse)
/// * column set column must be added if number of columns in total exceeds 1024
/// </summary>
public static SqlRandomTableColumn[] CreateRandTypes(SqlRandomizer rand, SqlRandomTypeInfoCollection sourceCollection, int maxColumnsCount, bool createIdColumn)
{
var retColumns = new List <SqlRandomTableColumn>(maxColumnsCount);
bool hasTimestamp = false;
double totalRowSize = 0;
int totalRegularColumns = 0;
bool hasColumnSet = false;
bool hasSparseColumns = false;
int maxRowSize = MaxBytesPerRow; // set to MaxBytesPerRowWithSparse when sparse column is first added
int i = 0;
if (createIdColumn)
{
SqlRandomTypeInfo keyType = sourceCollection[SqlDbType.Int];
SqlRandomTableColumn keyColumn = keyType.CreateDefaultColumn(SqlRandomColumnOptions.None);
retColumns.Add(keyColumn);
totalRowSize += keyType.GetInRowSize(keyColumn, null);
i++;
totalRegularColumns++;
}
for (; i < maxColumnsCount; i++)
{
// select column options (sparse/column-set)
bool isSparse; // must be set in the if/else flow below
bool isColumnSet = false;
if (totalRegularColumns >= MaxNonSparseColumns)
{
// reached the limit for regular columns
if (!hasColumnSet)
{
// no column-set yet, stop unconditionally
// this can happen if large char/binary value brought the row size total to a limit leaving no space for column-set
break;
}
// there is a column set, enforce sparse from this point
isSparse = true;
}
else if (i == (MaxNonSparseColumns - 1) && hasSparseColumns && !hasColumnSet)
{
// we almost reached the limit of regular & sparse columns with, but no column set added
// to increase chances for >1024 columns, enforce column set now
isColumnSet = true;
isSparse = false;
}
else if (totalRowSize > MaxBytesPerRowWithSparse)
{
Debug.Assert(totalRowSize <= MaxBytesPerRow, "size over the max limit");
Debug.Assert(!hasSparseColumns, "should not have sparse columns after MaxBytesPerRowWithSparse (check maxRowSize)");
// cannot insert sparse from this point
isSparse = false;
isColumnSet = false;
}
else
{
// check how close we are to the limit of the row size
int sparseProbability;
if (totalRowSize < 100)
{
sparseProbability = 2;
}
else if (totalRowSize < MaxBytesPerRowWithSparse / 2)
{
sparseProbability = 10;
}
else if (totalRowSize < (MaxBytesPerRowWithSparse - s_columnSetSafetyRange))
{
sparseProbability = 50;
}
else
{
// close to the row size limit, special case
if (!hasColumnSet)
{
// if we have not added column set column yet
// column-set is a regular column and its size counts towards row size, so time to add it
isColumnSet = true;
sparseProbability = -1; // not used
}
else
{
sparseProbability = 90;
}
}
if (!isColumnSet)
{
isSparse = (rand.Next(100) < sparseProbability);
if (!isSparse && !hasColumnSet)
{
// if decided to add regular column, give it a (low) chance to inject a column set at any position
isColumnSet = rand.Next(100) < 1;
}
}
else
{
isSparse = false;
}
}
// select the type
SqlRandomTypeInfo ti;
SqlRandomColumnOptions options = SqlRandomColumnOptions.None;
if (isSparse)
{
Debug.Assert(!isColumnSet, "should not have both sparse and column set flags set");
ti = sourceCollection.NextSparse(rand);
Debug.Assert(ti.CanBeSparseColumn, "NextSparse must return only types that can be sparse");
options |= SqlRandomColumnOptions.Sparse;
}
else if (isColumnSet)
{
Debug.Assert(!hasColumnSet, "there is already a column set, we should not set isColumnSet again above");
ti = sourceCollection[SqlDbType.Xml];
options |= SqlRandomColumnOptions.ColumnSet;
}
else
{
// regular column
ti = sourceCollection.Next(rand);
if (ti.Type == SqlDbType.Timestamp)
{
// while table can contain single timestamp column only, there is no way to insert values into it.
// thus, do not allow this
if (hasTimestamp || maxColumnsCount == 1)
{
ti = sourceCollection[SqlDbType.Int];
}
else
{
// table cannot have two timestamp columns
hasTimestamp = true;
}
}
}
SqlRandomTableColumn col = ti.CreateRandomColumn(rand, options);
if (!isSparse)
{
double rowSize = ti.GetInRowSize(col, DBNull.Value);
int overhead = GetRowOverhead(retColumns.Count + 1); // +1 for this column
if (totalRowSize + rowSize + overhead > maxRowSize)
{
// cannot use this column
// note that if this column is a column set column
continue;
}
totalRowSize += rowSize;
totalRegularColumns++;
}
// else - sparse columns are not counted towards row size when table is created (they are when inserting new row with non-null value in the sparse column)...
retColumns.Add(col);
// after adding the column, update the state
if (isColumnSet)
{
hasColumnSet = true;
}
if (isSparse)
{
hasSparseColumns = true;
maxRowSize = MaxBytesPerRowWithSparse; // reduce the max row size
}
}
return(retColumns.ToArray());
}
public double GetInRowSize(object value)
{
return(TypeInfo.GetInRowSize(this, value));
}