SQLxD Part 13 — Natural join – Random IT Utensils

This is the thirtieth part of the SQLxD series. For your convenience you can find other parts in the table of contents in Part 1 – XML Transformation

We mentioned the natural join a few times and it finally the part when we implement it. Here we go:

using System;
using System.Collections.Generic;
using System.Linq;
using Model;
using QueryLogic.Exceptions;
using QueryLogic.Expressions.RowExpressions;
using QueryLogic.Predicates;
using QueryLogic.Predicates.Complex;
using QueryLogic.Predicates.Simple;
using QueryLogic.RelationProviding;

namespace QueryLogic.Joins.Implementation
{
    public class NaturalJoin : InnerJoin
    {
        public NaturalJoin(IRelationProvider firstRelation, IRelationProvider secondRelation)
            : base(firstRelation, secondRelation, null)
        {
        }

        protected bool Equals(NaturalJoin other)
        {
            return base.Equals(other);
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj)) return false;
            if (ReferenceEquals(this, obj)) return true;
            if (obj.GetType() != GetType()) return false;
            return Equals((NaturalJoin)obj);
        }

        public override int GetHashCode()
        {
            return 0;
        }

        public override Relation CreateRelation(Node source)
        {
            var firstRelation = FirstRelation.CreateRelation(source);
            var secondRelation = SecondRelation.CreateRelation(source);
            return new Relation(firstRelation.Rows.SelectMany(firstRow => {
                return secondRelation.Rows.Select(secondRow =>
                {
                    return MatchRows(firstRelation, secondRelation, firstRow, secondRow);
                });
            }).Where(r => r != null));
        }

        private Row MatchRows(Relation firstRelation, Relation secondRelation, Row firstRow, Row secondRow)
        {
            if (firstRow.Guids.Count() < secondRow.Guids.Count())
            {
                return MatchParentToChild(firstRelation, secondRelation, firstRow, secondRow);
            }
            else
            {
                return MatchParentToChild(secondRelation, firstRelation, secondRow, firstRow);
            }
        }

        private Row MatchParentToChild(Relation firstRelation, Relation secondRelation, Row firstRow, Row secondRow)
        {
            ThrowIfAmbiguousGuidsInRelation(firstRelation, firstRow.Guids.Select(g => g.GuidHeader).OrderBy(g => g.Name));
            ThrowIfAmbiguousGuidsInRelation(secondRelation, secondRow.Guids.Select(g => g.GuidHeader).OrderBy(g => g.Name));

            foreach (GuidCell firstGuid in firstRow.Guids)
            {
                var anySecondGuid = secondRow.Guids.FirstOrDefault();
                var secondSchema = anySecondGuid != null ? anySecondGuid.GuidHeader.Schema : null; ;
                var secondGuid = secondRow.GetGuid(secondSchema, firstGuid.GuidHeader.Name);
                if (secondGuid == null || firstGuid.Guid != secondGuid.Guid)
                {
                    return null;
                }
            }

            var newRow = new Row();

            newRow.AddCells(firstRow.Cells);
            newRow.AddCells(secondRow.Cells);
            newRow.AddGuids(firstRow.Guids);
            newRow.AddGuids(secondRow.Guids);
            newRow.RemoveDuplicateGuidsByName();

            return newRow;
        }

        private void ThrowIfAmbiguousGuidsInRelation(Relation source, IOrderedEnumerable<GuidHeader> columns)
        {
            IEnumerable<Tuple<GuidHeader, GuidHeader>> pairs = columns.Zip(columns.Skip(1), Tuple.Create);

            foreach (var pair in pairs)
            {
                if (pair.Item1.Name == pair.Item2.Name)
                {
                    throw new AmbiguousGuidsInRelationException(source, pair.Item1.Name);
                }
            }
        }
    }
}

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using System;

using System.Collections.Generic;

using System.Linq;

using Model;

using QueryLogic.Exceptions;

using QueryLogic.Expressions.RowExpressions;

using QueryLogic.Predicates;

using QueryLogic.Predicates.Complex;

using QueryLogic.Predicates.Simple;

using QueryLogic.RelationProviding;

namespace QueryLogic.Joins.Implementation

{

public class NaturalJoin : InnerJoin

{

public NaturalJoin(IRelationProvider firstRelation, IRelationProvider secondRelation)

: base(firstRelation, secondRelation, null)

{

}

protected bool Equals(NaturalJoin other)

{

return base.Equals(other);

}

public override bool Equals(object obj)

{

if (ReferenceEquals(null, obj)) return false;

if (ReferenceEquals(this, obj)) return true;

if (obj.GetType() != GetType()) return false;

return Equals((NaturalJoin)obj);

}

public override int GetHashCode()

{

return 0;

}

public override Relation CreateRelation(Node source)

{

var firstRelation = FirstRelation.CreateRelation(source);

var secondRelation = SecondRelation.CreateRelation(source);

return new Relation(firstRelation.Rows.SelectMany(firstRow => {

return secondRelation.Rows.Select(secondRow =>

{

return MatchRows(firstRelation, secondRelation, firstRow, secondRow);

});

}).Where(r => r != null));

}

private Row MatchRows(Relation firstRelation, Relation secondRelation, Row firstRow, Row secondRow)

{

if (firstRow.Guids.Count() < secondRow.Guids.Count())

{

return MatchParentToChild(firstRelation, secondRelation, firstRow, secondRow);

}

else

{

return MatchParentToChild(secondRelation, firstRelation, secondRow, firstRow);

}

private Row MatchParentToChild(Relation firstRelation, Relation secondRelation, Row firstRow, Row secondRow)

{

ThrowIfAmbiguousGuidsInRelation(firstRelation, firstRow.Guids.Select(g => g.GuidHeader).OrderBy(g => g.Name));

ThrowIfAmbiguousGuidsInRelation(secondRelation, secondRow.Guids.Select(g => g.GuidHeader).OrderBy(g => g.Name));

foreach (GuidCell firstGuid in firstRow.Guids)

{

var anySecondGuid = secondRow.Guids.FirstOrDefault();

var secondSchema = anySecondGuid != null ? anySecondGuid.GuidHeader.Schema : null; ;

var secondGuid = secondRow.GetGuid(secondSchema, firstGuid.GuidHeader.Name);

if (secondGuid == null || firstGuid.Guid != secondGuid.Guid)

{

return null;

}

var newRow = new Row();

newRow.AddCells(firstRow.Cells);

newRow.AddCells(secondRow.Cells);

newRow.AddGuids(firstRow.Guids);

newRow.AddGuids(secondRow.Guids);

newRow.RemoveDuplicateGuidsByName();

return newRow;

}

private void ThrowIfAmbiguousGuidsInRelation(Relation source, IOrderedEnumerable<GuidHeader> columns)

{

IEnumerable<Tuple<GuidHeader, GuidHeader>> pairs = columns.Zip(columns.Skip(1), Tuple.Create);

foreach (var pair in pairs)

{

if (pair.Item1.Name == pair.Item2.Name)

{

throw new AmbiguousGuidsInRelationException(source, pair.Item1.Name);

}

First, we compare guid collection lengths. This is for checking whether it is possible for the relations to be in parent-child relation. Next, we find candidate for parent and start comparing guids. If all guids match then we can join rows.

And here are tests for this mechanism:

using System;
using System.Collections.Generic;
using System.Linq;
using Model;
using NUnit.Framework;
using QueryLogic.Exceptions;
using QueryLogic.Joins.Implementation;
using QueryLogic.Test.Mocks;

namespace QueryLogic.Test.Joins.Implementation
{
    [TestFixture]
    public class NaturalJoinTests
    {
        [Test]
        [ExpectedException(typeof(AmbiguousGuidsInRelationException))]
        public void CreateRelation_AmbiguousGuidsPassed_ShouldThrowAmbiguousGuidsInRelationException()
        {
            // Arrange
            var row11 = new Row();
            row11.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "a", Guid.NewGuid()),
                new GuidCell("schema2", "a", Guid.NewGuid()),
            });
            var firstRelation = new Relation();
            firstRelation.AddRow(row11);

            var row21 = new Row();
            row21.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "b", Guid.NewGuid()),
            });
            var secondRelation = new Relation();
            secondRelation.AddRow(row21);

            // Act
            // ReSharper disable once UnusedVariable
            Relation actual =
                new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))
                    .CreateRelation(null);
        }

        [Test]
        public void CreateRelation_MatchingGuidsPassed_ShouldReturnRelationWithMatchingGuids()
        {
            // Arrange
            Guid matchingGuid = Guid.NewGuid();

            var row11 = new Row();
            row11.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "a", matchingGuid)
            });
            row11.AddCells(new List<Cell>
            {
                new Cell(new ColumnHeader("schema", "a"), "a")
            });
            var row12 = new Row();
            row12.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "a", Guid.NewGuid())
            });
            var firstRelation = new Relation();
            firstRelation.AddRow(row11);
            firstRelation.AddRow(row12);

            var row21 = new Row();
            row21.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema2", "a", matchingGuid)
            });
            row21.AddCells(new List<Cell>
            {
                new Cell(new ColumnHeader("schema2", "a"), "a")
            });
            var row22 = new Row();
            row22.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema2", "a", Guid.NewGuid())
            });
            var secondRelation = new Relation();
            secondRelation.AddRow(row21);
            secondRelation.AddRow(row22);

            var expectedRow = new Row();
            expectedRow.AddCells(row11.Cells);
            expectedRow.AddCells(row21.Cells);
            var expectedRelation = new Relation();
            expectedRelation.AddRow(expectedRow);
            IEnumerable<Row> expected = expectedRelation.Rows;

            // Act
            IEnumerable<Row> actual =
                new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))
                    .CreateRelation(null).Rows;

            // Assert
            CollectionAssert.AreEquivalent(expected, actual);
        }

        [Test]
        public void CreateRelation_MatchingGuids_ShouldReturnRelationWithoutGuidsDuplicates()
        {
            // Arrange
            Guid matchingGuid = Guid.NewGuid();

            var row11 = new Row();
            row11.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "a", matchingGuid)
            });
            row11.AddCells(new List<Cell>
            {
                new Cell(new ColumnHeader("schema", "a"), "a")
            });
            var firstRelation = new Relation();
            firstRelation.AddRow(row11);

            var row21 = new Row();
            row21.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema2", "a", matchingGuid)
            });
            row21.AddCells(new List<Cell>
            {
                new Cell(new ColumnHeader("schema2", "a"), "a")
            });
            var secondRelation = new Relation();
            secondRelation.AddRow(row21);
            const int expected = 1;

            // Act
            int actual =
                new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))
                    .CreateRelation(null).Guids.Count();

            // Assert
            Assert.That(actual, Is.EqualTo(expected));
        }

        [Test]
        public void CreateRelation_RelationWithoutMatchingGuidsPassed_ShouldReturnEmptyRelation()
        {
            // Arrange
            var row11 = new Row();
            row11.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "a", Guid.NewGuid())
            });
            var firstRelation = new Relation();
            firstRelation.AddRow(row11);

            var row21 = new Row();
            row21.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "b", Guid.NewGuid())
            });
            var secondRelation = new Relation();
            secondRelation.AddRow(row21);

            // Act
            Relation actual =
                new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))
                    .CreateRelation(null);

            // Assert
            Assert.That(actual.Rows, Is.Empty);
        }

        [Test]
        public void CreateRelation_NodesOnMayLevels_ShouldMatchCorrectDescendants()
        {
            // Arrange
            var guidSzef = Guid.NewGuid();

            var guidOsoba1 = Guid.NewGuid();
            var guidOsoba2 = Guid.NewGuid();
            var guidOsoba3 = Guid.NewGuid();
            var guidOsoba4 = Guid.NewGuid();

            var row11 = new Row();
            row11.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.osoba",guidOsoba1)
            });
            var row12 = new Row();
            row12.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.osoba", guidOsoba1),
                new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2)
            });
            var row13 = new Row();
            row13.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.osoba", guidOsoba1),
                new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2),
                new GuidCell("schema1", "dok.osoba.osoba.osoba", guidOsoba3)
            });
            var row14 = new Row();
            row14.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.szef", guidSzef),
                new GuidCell("schema1", "dok.szef.osoba", guidOsoba4)
            });
            var firstRelation = new Relation();
            firstRelation.AddRow(row11);
            firstRelation.AddRow(row12);
            firstRelation.AddRow(row13);
            firstRelation.AddRow(row14);


            var guidMail1 = Guid.NewGuid();
            var guidMail2 = Guid.NewGuid();
            var guidMail3 = Guid.NewGuid();
            var guidMail4 = Guid.NewGuid();

            var row21 = new Row();
            row21.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.osoba", guidOsoba1),
                new GuidCell("schema1", "dok.osoba.mail", guidMail1)
            });
            var row22 = new Row();
            row22.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.osoba", guidOsoba1),
                new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2),
                new GuidCell("schema1", "dok.osoba.osoba.mail", guidMail2),
            });
            var row23 = new Row();
            row23.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.osoba", guidOsoba1),
                new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2),
                new GuidCell("schema1", "dok.osoba.osoba.osoba", guidOsoba3),
                new GuidCell("schema1", "dok.osoba.osoba.osoba.mail", guidMail3),
            });
            var row24 = new Row();
            row24.AddGuids(new List<GuidCell>
            {
                new GuidCell("schema1", "dok.szef", guidSzef),
                new GuidCell("schema1", "dok.szef.osoba", guidOsoba4),
                new GuidCell("schema1", "dok.szef.osoba.mail", guidMail4),
            });
            var secondRelation = new Relation();
            secondRelation.AddRow(row21);
            secondRelation.AddRow(row22);
            secondRelation.AddRow(row23);
            secondRelation.AddRow(row24);

            // Act
            Relation actual =
                new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))
                    .CreateRelation(null);

            // Assert
            Assert.That(actual.Rows.Count(), Is.EqualTo(7));
        }
    }
}

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using System;

using System.Collections.Generic;

using System.Linq;

using Model;

using NUnit.Framework;

using QueryLogic.Exceptions;

using QueryLogic.Joins.Implementation;

using QueryLogic.Test.Mocks;

namespace QueryLogic.Test.Joins.Implementation

{

[TestFixture]

public class NaturalJoinTests

{

[Test]

[ExpectedException(typeof(AmbiguousGuidsInRelationException))]

public void CreateRelation_AmbiguousGuidsPassed_ShouldThrowAmbiguousGuidsInRelationException()

{

// Arrange

var row11 = new Row();

row11.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "a", Guid.NewGuid()),

new GuidCell("schema2", "a", Guid.NewGuid()),

});

var firstRelation = new Relation();

firstRelation.AddRow(row11);

var row21 = new Row();

row21.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "b", Guid.NewGuid()),

});

var secondRelation = new Relation();

secondRelation.AddRow(row21);

// Act

// ReSharper disable once UnusedVariable

Relation actual =

new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))

.CreateRelation(null);

}

[Test]

public void CreateRelation_MatchingGuidsPassed_ShouldReturnRelationWithMatchingGuids()

{

// Arrange

Guid matchingGuid = Guid.NewGuid();

var row11 = new Row();

row11.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "a", matchingGuid)

});

row11.AddCells(new List<Cell>

{

new Cell(new ColumnHeader("schema", "a"), "a")

});

var row12 = new Row();

row12.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "a", Guid.NewGuid())

});

var firstRelation = new Relation();

firstRelation.AddRow(row11);

firstRelation.AddRow(row12);

var row21 = new Row();

row21.AddGuids(new List<GuidCell>

{

new GuidCell("schema2", "a", matchingGuid)

});

row21.AddCells(new List<Cell>

{

new Cell(new ColumnHeader("schema2", "a"), "a")

});

var row22 = new Row();

row22.AddGuids(new List<GuidCell>

{

new GuidCell("schema2", "a", Guid.NewGuid())

});

var secondRelation = new Relation();

secondRelation.AddRow(row21);

secondRelation.AddRow(row22);

var expectedRow = new Row();

expectedRow.AddCells(row11.Cells);

expectedRow.AddCells(row21.Cells);

var expectedRelation = new Relation();

expectedRelation.AddRow(expectedRow);

IEnumerable<Row> expected = expectedRelation.Rows;

// Act

IEnumerable<Row> actual =

new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))

.CreateRelation(null).Rows;

// Assert

CollectionAssert.AreEquivalent(expected, actual);

}

[Test]

public void CreateRelation_MatchingGuids_ShouldReturnRelationWithoutGuidsDuplicates()

{

// Arrange

Guid matchingGuid = Guid.NewGuid();

var row11 = new Row();

row11.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "a", matchingGuid)

});

row11.AddCells(new List<Cell>

{

new Cell(new ColumnHeader("schema", "a"), "a")

});

var firstRelation = new Relation();

firstRelation.AddRow(row11);

var row21 = new Row();

row21.AddGuids(new List<GuidCell>

{

new GuidCell("schema2", "a", matchingGuid)

});

row21.AddCells(new List<Cell>

{

new Cell(new ColumnHeader("schema2", "a"), "a")

});

var secondRelation = new Relation();

secondRelation.AddRow(row21);

const int expected = 1;

// Act

int actual =

new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))

.CreateRelation(null).Guids.Count();

// Assert

Assert.That(actual, Is.EqualTo(expected));

}

[Test]

public void CreateRelation_RelationWithoutMatchingGuidsPassed_ShouldReturnEmptyRelation()

{

// Arrange

var row11 = new Row();

row11.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "a", Guid.NewGuid())

});

var firstRelation = new Relation();

firstRelation.AddRow(row11);

var row21 = new Row();

row21.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "b", Guid.NewGuid())

});

var secondRelation = new Relation();

secondRelation.AddRow(row21);

// Act

Relation actual =

new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))

.CreateRelation(null);

// Assert

Assert.That(actual.Rows, Is.Empty);

}

[Test]

public void CreateRelation_NodesOnMayLevels_ShouldMatchCorrectDescendants()

{

// Arrange

var guidSzef = Guid.NewGuid();

var guidOsoba1 = Guid.NewGuid();

var guidOsoba2 = Guid.NewGuid();

var guidOsoba3 = Guid.NewGuid();

var guidOsoba4 = Guid.NewGuid();

var row11 = new Row();

row11.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.osoba",guidOsoba1)

});

var row12 = new Row();

row12.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.osoba", guidOsoba1),

new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2)

});

var row13 = new Row();

row13.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.osoba", guidOsoba1),

new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2),

new GuidCell("schema1", "dok.osoba.osoba.osoba", guidOsoba3)

});

var row14 = new Row();

row14.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.szef", guidSzef),

new GuidCell("schema1", "dok.szef.osoba", guidOsoba4)

});

var firstRelation = new Relation();

firstRelation.AddRow(row11);

firstRelation.AddRow(row12);

firstRelation.AddRow(row13);

firstRelation.AddRow(row14);

var guidMail1 = Guid.NewGuid();

var guidMail2 = Guid.NewGuid();

var guidMail3 = Guid.NewGuid();

var guidMail4 = Guid.NewGuid();

var row21 = new Row();

row21.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.osoba", guidOsoba1),

new GuidCell("schema1", "dok.osoba.mail", guidMail1)

});

var row22 = new Row();

row22.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.osoba", guidOsoba1),

new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2),

new GuidCell("schema1", "dok.osoba.osoba.mail", guidMail2),

});

var row23 = new Row();

row23.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.osoba", guidOsoba1),

new GuidCell("schema1", "dok.osoba.osoba", guidOsoba2),

new GuidCell("schema1", "dok.osoba.osoba.osoba", guidOsoba3),

new GuidCell("schema1", "dok.osoba.osoba.osoba.mail", guidMail3),

});

var row24 = new Row();

row24.AddGuids(new List<GuidCell>

{

new GuidCell("schema1", "dok.szef", guidSzef),

new GuidCell("schema1", "dok.szef.osoba", guidOsoba4),

new GuidCell("schema1", "dok.szef.osoba.mail", guidMail4),

});

var secondRelation = new Relation();

secondRelation.AddRow(row21);

secondRelation.AddRow(row22);

secondRelation.AddRow(row23);

secondRelation.AddRow(row24);

// Act

Relation actual =

new NaturalJoin(new DummyRelationProvider(firstRelation), new DummyRelationProvider(secondRelation))

.CreateRelation(null);

// Assert

Assert.That(actual.Rows.Count(), Is.EqualTo(7));

}

This concludes our JOIN journey. Next time we are going to implement grouping.