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Redo SQL tree pruning
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roji committed Dec 25, 2023
1 parent 5defd88 commit 76161c7
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61 changes: 38 additions & 23 deletions src/EFCore.Relational/Query/QuerySqlGenerator.cs
Original file line number Diff line number Diff line change
Expand Up @@ -182,9 +182,8 @@ private static bool IsNonComposedSetOperation(SelectExpression selectExpression)
&& selectExpression.Projection.Count == setOperation.Source1.Projection.Count
&& selectExpression.Projection.Select(
(pe, index) => pe.Expression is ColumnExpression column
&& string.Equals(column.TableAlias, setOperation.Alias, StringComparison.Ordinal)
&& string.Equals(
column.Name, setOperation.Source1.Projection[index].Alias, StringComparison.Ordinal))
&& column.TableAlias == setOperation.Alias
&& column.Name == setOperation.Source1.Projection[index].Alias)
.All(e => e);

/// <inheritdoc />
Expand Down Expand Up @@ -237,26 +236,8 @@ protected override Expression VisitSelect(SelectExpression selectExpression)
}

GenerateTop(selectExpression);

if (selectExpression.Projection.Any())
{
GenerateList(selectExpression.Projection, e => Visit(e));
}
else
{
GenerateEmptyProjection(selectExpression);
}

if (selectExpression.Tables.Any())
{
_relationalCommandBuilder.AppendLine().Append("FROM ");

GenerateList(selectExpression.Tables, e => Visit(e), sql => sql.AppendLine());
}
else
{
GeneratePseudoFromClause();
}
GenerateProjection(selectExpression);
GenerateTables(selectExpression);

if (selectExpression.Predicate != null)
{
Expand Down Expand Up @@ -1060,6 +1041,40 @@ protected virtual void GenerateTop(SelectExpression selectExpression)
{
}

/// <summary>
/// Generates the projection in the relational command
/// </summary>
/// <param name="selectExpression">A select expression to use.</param>
protected virtual void GenerateProjection(SelectExpression selectExpression)
{
if (selectExpression.Projection.Any())
{
GenerateList(selectExpression.Projection, e => Visit(e));
}
else
{
GenerateEmptyProjection(selectExpression);
}
}

/// <summary>
/// Generates the tables in the relational command
/// </summary>
/// <param name="selectExpression">A select expression to use.</param>
protected virtual void GenerateTables(SelectExpression selectExpression)
{
if (selectExpression.Tables.Any())
{
_relationalCommandBuilder.AppendLine().Append("FROM ");

GenerateList(selectExpression.Tables, e => Visit(e), sql => sql.AppendLine());
}
else
{
GeneratePseudoFromClause();
}
}

/// <summary>
/// Generates an ORDER BY clause in the relational command
/// </summary>
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ namespace Microsoft.EntityFrameworkCore.Query;
/// <inheritdoc />
public class RelationalQueryTranslationPostprocessor : QueryTranslationPostprocessor
{
private readonly SqlTreePruner _pruner = new();
private readonly bool _useRelationalNulls;

/// <summary>
Expand Down Expand Up @@ -39,7 +40,7 @@ public override Expression Process(Expression query)
query = base.Process(query);
query = new SelectExpressionProjectionApplyingExpressionVisitor(
((RelationalQueryCompilationContext)QueryCompilationContext).QuerySplittingBehavior).Visit(query);
query = new SelectExpressionPruningExpressionVisitor().Visit(query);
query = Prune(query);

#if DEBUG
// Verifies that all SelectExpression are marked as immutable after this point.
Expand All @@ -56,6 +57,13 @@ public override Expression Process(Expression query)
return query;
}

/// <summary>
/// Prunes unnecessarily objects from the SQL tree, e.g. tables which aren't referenced by any column.
/// Can be overridden by providers for provider-specific pruning.
/// </summary>
protected virtual Expression Prune(Expression query)
=> _pruner.Prune(query);

#if DEBUG
private sealed class SelectExpressionMutableVerifyingExpressionVisitor : ExpressionVisitor
{
Expand All @@ -64,7 +72,7 @@ private sealed class SelectExpressionMutableVerifyingExpressionVisitor : Express
{
switch (expression)
{
case SelectExpression selectExpression when selectExpression.IsMutable():
case SelectExpression { IsMutable: true } selectExpression:
throw new InvalidDataException(selectExpression.Print());

case ShapedQueryExpression shapedQueryExpression:
Expand Down Expand Up @@ -123,7 +131,8 @@ public Expression EntryPoint(Expression expression)

if (expression is SelectExpression selectExpression)
{
foreach (var alias in selectExpression.RemovedAliases())
Check.DebugAssert(selectExpression.RemovedAliases is not null, "RemovedAliases not set");
foreach (var alias in selectExpression.RemovedAliases)
{
_usedAliases.Add(alias);
}
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,7 @@ protected override Expression VisitChildren(ExpressionVisitor visitor)
/// <param name="source1">The <see cref="SetOperationBase.Source1" /> property of the result.</param>
/// <param name="source2">The <see cref="SetOperationBase.Source2" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public virtual ExceptExpression Update(SelectExpression source1, SelectExpression source2)
public override ExceptExpression Update(SelectExpression source1, SelectExpression source2)
=> source1 != Source1 || source2 != Source2
? new ExceptExpression(Alias, source1, source2, IsDistinct, GetAnnotations())
: this;
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -24,12 +24,8 @@ public ExistsExpression(
RelationalTypeMapping? typeMapping)
: base(typeof(bool), typeMapping)
{
#if DEBUG
if (subquery.IsMutable())
{
throw new InvalidOperationException();
}
#endif
Check.DebugAssert(!subquery.IsMutable, "Mutable subquery provided to ExistsExpression");

Subquery = subquery;
}

Expand Down
8 changes: 2 additions & 6 deletions src/EFCore.Relational/Query/SqlExpressions/InExpression.cs
Original file line number Diff line number Diff line change
Expand Up @@ -66,12 +66,8 @@ private InExpression(
RelationalTypeMapping? typeMapping)
: base(typeof(bool), typeMapping)
{
#if DEBUG
if (subquery?.IsMutable() == true)
{
throw new InvalidOperationException();
}
#endif
Check.DebugAssert(subquery?.IsMutable != true, "Mutable subquery provided to ExistsExpression");

Item = item;
Subquery = subquery;
Values = values;
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -32,15 +32,6 @@ private InnerJoinExpression(
{
}

/// <inheritdoc />
protected override Expression VisitChildren(ExpressionVisitor visitor)
{
var table = (TableExpressionBase)visitor.Visit(Table);
var joinPredicate = (SqlExpression)visitor.Visit(JoinPredicate);

return Update(table, joinPredicate);
}

/// <summary>
/// Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will
/// return this expression.
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,7 @@ protected override Expression VisitChildren(ExpressionVisitor visitor)
/// <param name="source1">The <see cref="SetOperationBase.Source1" /> property of the result.</param>
/// <param name="source2">The <see cref="SetOperationBase.Source2" /> property of the result.</param>
/// <returns>This expression if no children changed, or an expression with the updated children.</returns>
public virtual IntersectExpression Update(SelectExpression source1, SelectExpression source2)
public override IntersectExpression Update(SelectExpression source1, SelectExpression source2)
=> source1 != Source1 || source2 != Source2
? new IntersectExpression(Alias, source1, source2, IsDistinct, GetAnnotations())
: this;
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -32,15 +32,6 @@ private LeftJoinExpression(
{
}

/// <inheritdoc />
protected override Expression VisitChildren(ExpressionVisitor visitor)
{
var table = (TableExpressionBase)visitor.Visit(Table);
var joinPredicate = (SqlExpression)visitor.Visit(JoinPredicate);

return Update(table, joinPredicate);
}

/// <summary>
/// Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will
/// return this expression.
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,15 @@ protected PredicateJoinExpressionBase(
/// </summary>
public virtual SqlExpression JoinPredicate { get; }

/// <inheritdoc />
protected override Expression VisitChildren(ExpressionVisitor visitor)
{
var table = (TableExpressionBase)visitor.Visit(Table);
var joinPredicate = (SqlExpression)visitor.Visit(JoinPredicate);

return Update(table, joinPredicate);
}

/// <summary>
/// Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will
/// return this expression.
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -32,18 +32,13 @@ private ScalarSubqueryExpression(SelectExpression subquery, RelationalTypeMappin

private static SelectExpression Verify(SelectExpression selectExpression)
{
Check.DebugAssert(!selectExpression.IsMutable, "Mutable subquery provided to ExistsExpression");

if (selectExpression.Projection.Count != 1)
{
throw new InvalidOperationException(CoreStrings.TranslationFailed(selectExpression.Print()));
}

#if DEBUG
if (selectExpression.IsMutable())
{
throw new InvalidOperationException();
}
#endif

return selectExpression;
}

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -270,83 +270,6 @@ public EnclosingTermFindingVisitor(HashSet<SqlExpression> correlatedTerms)
}
}

private sealed class ColumnExpressionFindingExpressionVisitor : ExpressionVisitor
{
private Dictionary<string, HashSet<string>?>? _columnReferenced;
private Dictionary<string, HashSet<string>?>? _columnsUsedInJoinCondition;

public Dictionary<string, HashSet<string>?> FindColumns(SelectExpression selectExpression)
{
_columnReferenced = new Dictionary<string, HashSet<string>?>();
_columnsUsedInJoinCondition = new Dictionary<string, HashSet<string>?>();

foreach (var table in selectExpression.Tables)
{
var tableAlias = table is JoinExpressionBase joinExpressionBase
? joinExpressionBase.Table.Alias!
: table.Alias!;
_columnReferenced[tableAlias] = null;
}

Visit(selectExpression);

foreach (var keyValuePair in _columnsUsedInJoinCondition)
{
var tableAlias = keyValuePair.Key;
if (_columnReferenced[tableAlias] != null
&& _columnsUsedInJoinCondition[tableAlias] != null)
{
_columnReferenced[tableAlias]!.UnionWith(_columnsUsedInJoinCondition[tableAlias]!);
}
}

return _columnReferenced;
}

[return: NotNullIfNotNull("expression")]
public override Expression? Visit(Expression? expression)
{
switch (expression)
{
case ColumnExpression columnExpression:
var tableAlias = columnExpression.TableAlias;
if (_columnReferenced!.ContainsKey(tableAlias))
{
_columnReferenced[tableAlias] ??= new HashSet<string>();

_columnReferenced[tableAlias]!.Add(columnExpression.Name);
}

// Always skip the table of ColumnExpression since it will traverse into deeper subquery
return columnExpression;

case PredicateJoinExpressionBase predicateJoinExpressionBase:
var predicateJoinTableAlias = predicateJoinExpressionBase.Table.Alias!;
// Visiting the join predicate will add some columns for join table.
// But if all the referenced columns are in join predicate only then we can remove the join table.
// So if there are no referenced columns yet means there is still potential to remove this table,
// In such case we moved the columns encountered in join predicate to other dictionary and later merge
// if there are more references to the join table outside of join predicate.
// We should also remove references to the outer if this column gets removed then that subquery can also remove projections
// But currently we only remove table for TPT & entity splitting scenario
// in which there are all table expressions which connects via joins.
var joinOnSameLevel = _columnReferenced!.ContainsKey(predicateJoinTableAlias);
var noReferences = !joinOnSameLevel || _columnReferenced[predicateJoinTableAlias] == null;
base.Visit(predicateJoinExpressionBase);
if (noReferences && joinOnSameLevel)
{
_columnsUsedInJoinCondition![predicateJoinTableAlias] = _columnReferenced[predicateJoinTableAlias];
_columnReferenced[predicateJoinTableAlias] = null;
}

return predicateJoinExpressionBase;

default:
return base.Visit(expression);
}
}
}

private sealed class TableReferenceUpdatingExpressionVisitor : ExpressionVisitor
{
private readonly SelectExpression _oldSelect;
Expand Down
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