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Implement set operations (Union, Intersect...).
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Navigation/include support not included.

Fixes dotnet#6812
Fixes dotnet#12549
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@roji
roji committed Jun 24, 2019
1 parent e649a72 commit d8766e9
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Showing 15 changed files with 1,010 additions and 95 deletions.
6 changes: 6 additions & 0 deletions src/EFCore.Relational/Properties/RelationalStrings.Designer.cs
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5 changes: 4 additions & 1 deletion src/EFCore.Relational/Properties/RelationalStrings.resx
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Original file line number Diff line number Diff line change
Expand Up @@ -481,4 +481,7 @@
<data name="PendingAmbientTransaction" xml:space="preserve">
<value>This connection was used with an ambient transaction. The original ambient transaction needs to be completed before this connection can be used outside of it.</value>
</data>
</root>
<data name="SetOperationNotWithinEntityTypeHierarchy" xml:space="preserve">
<value>Set operations (Union, Concat, Intersect, Except) are only supported over entity types within the same type hierarchy.</value>
</data>
</root>
128 changes: 103 additions & 25 deletions src/EFCore.Relational/Query/Pipeline/QuerySqlGenerator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.SqlExpressions;
Expand Down Expand Up @@ -79,6 +80,28 @@ protected override Expression VisitSelect(SelectExpression selectExpression)
subQueryIndent = _relationalCommandBuilder.Indent();
}

if (selectExpression.IsSetOperation)
{
GenerateSetOperation(selectExpression);
}
else
{
GenerateSelect(selectExpression);
}

if (selectExpression.Alias != null)
{
subQueryIndent.Dispose();

_relationalCommandBuilder.AppendLine()
.Append(") AS " + _sqlGenerationHelper.DelimitIdentifier(selectExpression.Alias));
}

return selectExpression;
}

protected virtual void GenerateSelect(SelectExpression selectExpression)
{
_relationalCommandBuilder.Append("SELECT ");

if (selectExpression.IsDistinct)
Expand Down Expand Up @@ -111,40 +134,65 @@ protected override Expression VisitSelect(SelectExpression selectExpression)
Visit(selectExpression.Predicate);
}

if (selectExpression.Orderings.Any())
{
var orderings = selectExpression.Orderings.ToList();
GenerateOrderings(selectExpression);
GenerateLimitOffset(selectExpression);
}

if (selectExpression.Limit == null
&& selectExpression.Offset == null)
{
orderings.RemoveAll(oe => oe.Expression is SqlConstantExpression || oe.Expression is SqlParameterExpression);
}
protected virtual void GenerateSetOperation(SelectExpression setOperationExpression)
{
Debug.Assert(setOperationExpression.Tables.Count == 2,
$"{nameof(SelectExpression)} with {setOperationExpression.Tables.Count} tables, must be 2");

if (orderings.Count > 0)
{
_relationalCommandBuilder.AppendLine()
.Append("ORDER BY ");
GenerateSetOperationOperand(setOperationExpression, (SelectExpression)setOperationExpression.Tables[0]);

GenerateList(orderings, e => Visit(e));
_relationalCommandBuilder
.AppendLine()
.AppendLine(GenerateSetOperationType(setOperationExpression.SetOperationType));

GenerateSetOperationOperand(setOperationExpression, (SelectExpression)setOperationExpression.Tables[1]);

GenerateOrderings(setOperationExpression);
GenerateLimitOffset(setOperationExpression);
}

private static string GenerateSetOperationType(SetOperationType setOperationType)
=> setOperationType switch {
SetOperationType.Union => "UNION",
SetOperationType.UnionAll => "UNION ALL",
SetOperationType.Intersect => "INTERSECT",
SetOperationType.Except => "EXCEPT",
_ => throw new NotSupportedException($"Invalid {nameof(SetOperationType)}: {setOperationType}")
};

protected virtual void GenerateSetOperationOperand(
SelectExpression setOperationExpression,
SelectExpression operandExpression)
{
var parensOpened = false;
IDisposable indent = null;
if (operandExpression.IsSetOperation)
{
// INTERSECT has higher precedence over UNION and EXCEPT, but otherwise evaluation is left-to-right.
// To preserve meaning, add parentheses whenever a set operation is nested within a different set operation.
if (operandExpression.SetOperationType != setOperationExpression.SetOperationType)
{
_relationalCommandBuilder.AppendLine("(");
parensOpened = true;
indent = _relationalCommandBuilder.Indent();
}
}
else if (selectExpression.Offset != null)
else
{
_relationalCommandBuilder.AppendLine().Append("ORDER BY (SELECT 1)");
indent = _relationalCommandBuilder.Indent();
}

GenerateLimitOffset(selectExpression);
Visit(operandExpression);

if (selectExpression.Alias != null)
indent?.Dispose();
if (parensOpened)
{
subQueryIndent.Dispose();

_relationalCommandBuilder.AppendLine()
.Append(") AS " + _sqlGenerationHelper.DelimitIdentifier(selectExpression.Alias));
_relationalCommandBuilder.AppendLine().Append(")");
}

return selectExpression;
}

protected override Expression VisitProjection(ProjectionExpression projectionExpression)
Expand Down Expand Up @@ -198,9 +246,13 @@ protected override Expression VisitSqlFunction(SqlFunctionExpression sqlFunction

protected override Expression VisitColumn(ColumnExpression columnExpression)
{
if (columnExpression.Table.Alias != null)
{
_relationalCommandBuilder
.Append(_sqlGenerationHelper.DelimitIdentifier(columnExpression.Table.Alias))
.Append(".");
}
_relationalCommandBuilder
.Append(_sqlGenerationHelper.DelimitIdentifier(columnExpression.Table.Alias))
.Append(".")
.Append(_sqlGenerationHelper.DelimitIdentifier(columnExpression.Name));

return columnExpression;
Expand Down Expand Up @@ -538,6 +590,32 @@ protected virtual void GenerateTop(SelectExpression selectExpression)
{
}

protected virtual void GenerateOrderings(SelectExpression selectExpression)
{
if (selectExpression.Orderings.Any())
{
var orderings = selectExpression.Orderings.ToList();

if (selectExpression.Limit == null
&& selectExpression.Offset == null)
{
orderings.RemoveAll(oe => oe.Expression is SqlConstantExpression || oe.Expression is SqlParameterExpression);
}

if (orderings.Count > 0)
{
_relationalCommandBuilder.AppendLine()
.Append("ORDER BY ");

GenerateList(orderings, e => Visit(e));
}
}
else if (selectExpression.Offset != null)
{
_relationalCommandBuilder.AppendLine().Append("ORDER BY (SELECT 1)");
}
}

protected virtual void GenerateLimitOffset(SelectExpression selectExpression)
{
// The below implements ISO SQL:2008
Expand Down
33 changes: 29 additions & 4 deletions ...EFCore.Relational/Query/Pipeline/RelationalQueryableMethodTranslatingExpressionVisitor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
using Microsoft.EntityFrameworkCore.Query.Pipeline;
using Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.SqlExpressions;
using System.Diagnostics;
using Microsoft.EntityFrameworkCore.Storage;

namespace Microsoft.EntityFrameworkCore.Relational.Query.Pipeline
{
Expand Down Expand Up @@ -150,7 +151,13 @@ protected override ShapedQueryExpression TranslateCast(ShapedQueryExpression sou
return source;
}

protected override ShapedQueryExpression TranslateConcat(ShapedQueryExpression source1, ShapedQueryExpression source2) => throw new NotImplementedException();
protected override ShapedQueryExpression TranslateConcat(ShapedQueryExpression source1, ShapedQueryExpression source2)
{
var operand1 = (SelectExpression)source1.QueryExpression;
var operand2 = (SelectExpression)source2.QueryExpression;
source1.ShaperExpression = operand1.ApplySetOperation(SetOperationType.UnionAll, operand2, source1.ShaperExpression);
return source1;
}

protected override ShapedQueryExpression TranslateContains(ShapedQueryExpression source, Expression item)
{
Expand Down Expand Up @@ -212,7 +219,13 @@ protected override ShapedQueryExpression TranslateDistinct(ShapedQueryExpression

protected override ShapedQueryExpression TranslateElementAtOrDefault(ShapedQueryExpression source, Expression index, bool returnDefault) => throw new NotImplementedException();

protected override ShapedQueryExpression TranslateExcept(ShapedQueryExpression source1, ShapedQueryExpression source2) => throw new NotImplementedException();
protected override ShapedQueryExpression TranslateExcept(ShapedQueryExpression source1, ShapedQueryExpression source2)
{
var operand1 = (SelectExpression)source1.QueryExpression;
var operand2 = (SelectExpression)source2.QueryExpression;
source1.ShaperExpression = operand1.ApplySetOperation(SetOperationType.Except, operand2, source1.ShaperExpression);
return source1;
}

protected override ShapedQueryExpression TranslateFirstOrDefault(ShapedQueryExpression source, LambdaExpression predicate, Type returnType, bool returnDefault)
{
Expand Down Expand Up @@ -279,7 +292,13 @@ protected override ShapedQueryExpression TranslateGroupJoin(ShapedQueryExpressio
throw new NotImplementedException();
}

protected override ShapedQueryExpression TranslateIntersect(ShapedQueryExpression source1, ShapedQueryExpression source2) => throw new NotImplementedException();
protected override ShapedQueryExpression TranslateIntersect(ShapedQueryExpression source1, ShapedQueryExpression source2)
{
var operand1 = (SelectExpression)source1.QueryExpression;
var operand2 = (SelectExpression)source2.QueryExpression;
source1.ShaperExpression = operand1.ApplySetOperation(SetOperationType.Intersect, operand2, source1.ShaperExpression);
return source1;
}

protected override ShapedQueryExpression TranslateJoin(
ShapedQueryExpression outer,
Expand Down Expand Up @@ -730,7 +749,13 @@ protected override ShapedQueryExpression TranslateThenBy(ShapedQueryExpression s
throw new InvalidOperationException();
}

protected override ShapedQueryExpression TranslateUnion(ShapedQueryExpression source1, ShapedQueryExpression source2) => throw new NotImplementedException();
protected override ShapedQueryExpression TranslateUnion(ShapedQueryExpression source1, ShapedQueryExpression source2)
{
var operand1 = (SelectExpression)source1.QueryExpression;
var operand2 = (SelectExpression)source2.QueryExpression;
source1.ShaperExpression = operand1.ApplySetOperation(SetOperationType.Union, operand2, source1.ShaperExpression);
return source1;
}

protected override ShapedQueryExpression TranslateWhere(ShapedQueryExpression source, LambdaExpression predicate)
{
Expand Down
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