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Improvements to the Merge routine #5778

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merged 4 commits into from
May 6, 2021
Merged

Improvements to the Merge routine #5778

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657b488
Handle nulls better in Merge
Apr 30, 2021
f0c0daa
sq
Apr 30, 2021
a3d211f
sq
Apr 30, 2021
822385c
Add unit test
May 5, 2021
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26 changes: 17 additions & 9 deletions src/Microsoft.Data.Analysis/ArrowStringDataFrameColumn.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -460,34 +460,42 @@ private ArrowStringDataFrameColumn Clone(PrimitiveDataFrameColumn<int> mapIndice
/// <inheritdoc/>
public override DataFrame ValueCounts()
{
Dictionary<string, ICollection<long>> groupedValues = GroupColumnValues<string>();
Dictionary<string, ICollection<long>> groupedValues = GroupColumnValues<string>(out HashSet<long> _);
return StringDataFrameColumn.ValueCountsImplementation(groupedValues);
}

/// <inheritdoc/>
public override GroupBy GroupBy(int columnIndex, DataFrame parent)
{
Dictionary<string, ICollection<long>> dictionary = GroupColumnValues<string>();
Dictionary<string, ICollection<long>> dictionary = GroupColumnValues<string>(out HashSet<long> _);
return new GroupBy<string>(parent, columnIndex, dictionary);
}

/// <inheritdoc/>
public override Dictionary<TKey, ICollection<long>> GroupColumnValues<TKey>()
public override Dictionary<TKey, ICollection<long>> GroupColumnValues<TKey>(out HashSet<long> nullIndices)
{
if (typeof(TKey) == typeof(string))
{
nullIndices = new HashSet<long>();
Dictionary<string, ICollection<long>> multimap = new Dictionary<string, ICollection<long>>(EqualityComparer<string>.Default);
for (long i = 0; i < Length; i++)
{
string str = this[i] ?? "__null__";
bool containsKey = multimap.TryGetValue(str, out ICollection<long> values);
if (containsKey)
string str = this[i];
if (str != null)
{
values.Add(i);
bool containsKey = multimap.TryGetValue(str, out ICollection<long> values);
if (containsKey)
{
values.Add(i);
}
else
{
multimap.Add(str, new List<long>() { i });
}
}
else
{
multimap.Add(str, new List<long>() { i });
nullIndices.Add(i);
}
}
return multimap as Dictionary<TKey, ICollection<long>>;
Expand All @@ -499,7 +507,7 @@ public override Dictionary<TKey, ICollection<long>> GroupColumnValues<TKey>()
}

/// <inheritdoc/>
public ArrowStringDataFrameColumn FillNulls(string value, bool inPlace = false)
public ArrowStringDataFrameColumn FillNulls(string value, bool inPlace = false)
{
if (value == null)
{
Expand Down
183 changes: 91 additions & 92 deletions src/Microsoft.Data.Analysis/DataFrame.Join.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -168,82 +168,72 @@ public DataFrame Merge<TKey>(DataFrame other, string leftJoinColumn, string righ
{
// First hash other dataframe on the rightJoinColumn
DataFrameColumn otherColumn = other.Columns[rightJoinColumn];
Dictionary<TKey, ICollection<long>> multimap = otherColumn.GroupColumnValues<TKey>();
Dictionary<TKey, ICollection<long>> multimap = otherColumn.GroupColumnValues<TKey>(out HashSet<long> otherColumnNullIndices);

// Go over the records in this dataframe and match with the dictionary
DataFrameColumn thisColumn = Columns[leftJoinColumn];

for (long i = 0; i < thisColumn.Length; i++)
{
var thisColumnValue = thisColumn[i];
TKey thisColumnValueOrDefault = (TKey)(thisColumnValue == null ? default(TKey) : thisColumnValue);
if (multimap.TryGetValue(thisColumnValueOrDefault, out ICollection<long> rowNumbers))
if (thisColumnValue != null)
{
foreach (long row in rowNumbers)
if (multimap.TryGetValue((TKey)thisColumnValue, out ICollection<long> rowNumbers))
{
if (thisColumnValue == null)
foreach (long row in rowNumbers)
{
// Match only with nulls in otherColumn
if (otherColumn[row] == null)
{
leftRowIndices.Append(i);
rightRowIndices.Append(row);
}
}
else
{
// Cannot match nulls in otherColumn
if (otherColumn[row] != null)
{
leftRowIndices.Append(i);
rightRowIndices.Append(row);
}
leftRowIndices.Append(i);
rightRowIndices.Append(row);
}
}
else
{
leftRowIndices.Append(i);
rightRowIndices.Append(null);
}
}
else
{
leftRowIndices.Append(i);
rightRowIndices.Append(null);
foreach (long row in otherColumnNullIndices)
{
leftRowIndices.Append(i);
rightRowIndices.Append(row);
}
}
}
}
else if (joinAlgorithm == JoinAlgorithm.Right)
{
DataFrameColumn thisColumn = Columns[leftJoinColumn];
Dictionary<TKey, ICollection<long>> multimap = thisColumn.GroupColumnValues<TKey>();
Dictionary<TKey, ICollection<long>> multimap = thisColumn.GroupColumnValues<TKey>(out HashSet<long> thisColumnNullIndices);

DataFrameColumn otherColumn = other.Columns[rightJoinColumn];
for (long i = 0; i < otherColumn.Length; i++)
{
var otherColumnValue = otherColumn[i];
TKey otherColumnValueOrDefault = (TKey)(otherColumnValue == null ? default(TKey) : otherColumnValue);
if (multimap.TryGetValue(otherColumnValueOrDefault, out ICollection<long> rowNumbers))
if (otherColumnValue != null)
{
foreach (long row in rowNumbers)
if (multimap.TryGetValue((TKey)otherColumnValue, out ICollection<long> rowNumbers))
{
if (otherColumnValue == null)
foreach (long row in rowNumbers)
{
if (thisColumn[row] == null)
{
leftRowIndices.Append(row);
rightRowIndices.Append(i);
}
}
else
{
if (thisColumn[row] != null)
{
leftRowIndices.Append(row);
rightRowIndices.Append(i);
}
leftRowIndices.Append(row);
rightRowIndices.Append(i);
}
}
else
{
leftRowIndices.Append(null);
rightRowIndices.Append(i);
}
}
else
{
leftRowIndices.Append(null);
rightRowIndices.Append(i);
foreach (long thisColumnNullIndex in thisColumnNullIndices)
{
leftRowIndices.Append(thisColumnNullIndex);
rightRowIndices.Append(i);
}
}
}
}
Expand All @@ -253,97 +243,106 @@ public DataFrame Merge<TKey>(DataFrame other, string leftJoinColumn, string righ
long leftRowCount = Rows.Count;
long rightRowCount = other.Rows.Count;

var leftColumnIsSmaller = (leftRowCount <= rightRowCount);
bool leftColumnIsSmaller = leftRowCount <= rightRowCount;
DataFrameColumn hashColumn = leftColumnIsSmaller ? Columns[leftJoinColumn] : other.Columns[rightJoinColumn];
DataFrameColumn otherColumn = ReferenceEquals(hashColumn, Columns[leftJoinColumn]) ? other.Columns[rightJoinColumn] : Columns[leftJoinColumn];
Dictionary<TKey, ICollection<long>> multimap = hashColumn.GroupColumnValues<TKey>();
Dictionary<TKey, ICollection<long>> multimap = hashColumn.GroupColumnValues<TKey>(out HashSet<long> smallerDataFrameColumnNullIndices);

for (long i = 0; i < otherColumn.Length; i++)
{
var otherColumnValue = otherColumn[i];
TKey otherColumnValueOrDefault = (TKey)(otherColumnValue == null ? default(TKey) : otherColumnValue);
if (multimap.TryGetValue(otherColumnValueOrDefault, out ICollection<long> rowNumbers))
if (otherColumnValue != null)
{
foreach (long row in rowNumbers)
if (multimap.TryGetValue((TKey)otherColumnValue, out ICollection<long> rowNumbers))
{
if (otherColumnValue == null)
{
if (hashColumn[row] == null)
{
leftRowIndices.Append(leftColumnIsSmaller ? row : i);
rightRowIndices.Append(leftColumnIsSmaller ? i : row);
}
}
else
foreach (long row in rowNumbers)
{
if (hashColumn[row] != null)
{
leftRowIndices.Append(leftColumnIsSmaller ? row : i);
rightRowIndices.Append(leftColumnIsSmaller ? i : row);
}
leftRowIndices.Append(leftColumnIsSmaller ? row : i);
rightRowIndices.Append(leftColumnIsSmaller ? i : row);
}
}
}
else
{
foreach (long nullIndex in smallerDataFrameColumnNullIndices)
{
leftRowIndices.Append(leftColumnIsSmaller ? nullIndex : i);
rightRowIndices.Append(leftColumnIsSmaller ? i : nullIndex);
}
}
}
}
else if (joinAlgorithm == JoinAlgorithm.FullOuter)
{
DataFrameColumn otherColumn = other.Columns[rightJoinColumn];
Dictionary<TKey, ICollection<long>> multimap = otherColumn.GroupColumnValues<TKey>();
Dictionary<TKey, ICollection<long>> multimap = otherColumn.GroupColumnValues<TKey>(out HashSet<long> otherColumnNullIndices);
Dictionary<TKey, long> intersection = new Dictionary<TKey, long>(EqualityComparer<TKey>.Default);

// Go over the records in this dataframe and match with the dictionary
DataFrameColumn thisColumn = Columns[leftJoinColumn];
Int64DataFrameColumn thisColumnNullIndices = new Int64DataFrameColumn("ThisColumnNullIndices");

for (long i = 0; i < thisColumn.Length; i++)
{
var thisColumnValue = thisColumn[i];
TKey thisColumnValueOrDefault = (TKey)(thisColumnValue == null ? default(TKey) : thisColumnValue);
if (multimap.TryGetValue(thisColumnValueOrDefault, out ICollection<long> rowNumbers))
if (thisColumnValue != null)
{
foreach (long row in rowNumbers)
if (multimap.TryGetValue((TKey)thisColumnValue, out ICollection<long> rowNumbers))
{
if (thisColumnValue == null)
{
// Has to match only with nulls in otherColumn
if (otherColumn[row] == null)
{
leftRowIndices.Append(i);
rightRowIndices.Append(row);
if (!intersection.ContainsKey(thisColumnValueOrDefault))
{
intersection.Add(thisColumnValueOrDefault, rowNumber);
}
}
}
else
foreach (long row in rowNumbers)
{
// Cannot match to nulls in otherColumn
if (otherColumn[row] != null)
leftRowIndices.Append(i);
rightRowIndices.Append(row);
if (!intersection.ContainsKey((TKey)thisColumnValue))
{
leftRowIndices.Append(i);
rightRowIndices.Append(row);
if (!intersection.ContainsKey(thisColumnValueOrDefault))
{
intersection.Add(thisColumnValueOrDefault, rowNumber);
}
intersection.Add((TKey)thisColumnValue, rowNumber);
}
}
}
else
{
leftRowIndices.Append(i);
rightRowIndices.Append(null);
}
}
else
{
leftRowIndices.Append(i);
rightRowIndices.Append(null);
thisColumnNullIndices.Append(i);
}
}
for (long i = 0; i < otherColumn.Length; i++)
{
TKey value = (TKey)(otherColumn[i] ?? default(TKey));
if (!intersection.ContainsKey(value))
var value = otherColumn[i];
if (value != null)
{
if (!intersection.ContainsKey((TKey)value))
{
leftRowIndices.Append(null);
rightRowIndices.Append(i);
}
}
}

// Now handle the null rows
foreach (long? thisColumnNullIndex in thisColumnNullIndices)
{
foreach (long otherColumnNullIndex in otherColumnNullIndices)
{
leftRowIndices.Append(thisColumnNullIndex.Value);
rightRowIndices.Append(otherColumnNullIndex);
}
if (otherColumnNullIndices.Count == 0)
{
leftRowIndices.Append(thisColumnNullIndex.Value);
rightRowIndices.Append(null);
}
}
if (thisColumnNullIndices.Length == 0)
{
foreach (long otherColumnNullIndex in otherColumnNullIndices)
{
leftRowIndices.Append(null);
rightRowIndices.Append(i);
rightRowIndices.Append(otherColumnNullIndex);
}
}
}
Expand Down
7 changes: 6 additions & 1 deletion src/Microsoft.Data.Analysis/DataFrameColumn.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -203,7 +203,12 @@ public virtual DataFrameColumn Sort(bool ascending = true)
return Clone(sortIndices, !ascending, NullCount);
}

public virtual Dictionary<TKey, ICollection<long>> GroupColumnValues<TKey>() => throw new NotImplementedException();
/// <summary>
/// Groups the rows of this column by their value.
/// </summary>
/// <typeparam name="TKey">The type of data held by this column</typeparam>
/// <returns>A mapping of value(<typeparamref name="TKey"/>) to the indices containing this value</returns>
public virtual Dictionary<TKey, ICollection<long>> GroupColumnValues<TKey>(out HashSet<long> nullIndices) => throw new NotImplementedException();

/// <summary>
/// Returns a DataFrame containing counts of unique values
Expand Down
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