From 9698d589e4c2b489f406fe1a823d4bb42c322f71 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Dan=20Vr=C3=A1til?= <dvratil@redhat.com>

Date: Fri, 5 Dec 2014 18:21:18 +0100

Subject: [PATCH 21/30] Implement support for CASE...WHEN...THEN SQL statements

 SELECT columns

CASE...WHEN...THEN is a useful construct especially for aggregation

queries.

---

 server/src/storage/query.cpp               | 38 ++++++++++++++++++++++++++++++

 server/src/storage/query.h                 | 19 +++++++++++++++

 server/src/storage/querybuilder.cpp        | 30 +++++++++++++++++++++++

 server/src/storage/querybuilder.h          | 14 +++++++++++

 server/tests/unittest/querybuildertest.cpp | 38 +++++++++++++++++++++++++++++-

 5 files changed, 138 insertions(+), 1 deletion(-)

diff --git a/server/src/storage/query.cpp b/server/src/storage/query.cpp

index 6fb6c6e..c938ade 100644

--- a/server/src/storage/query.cpp

+++ b/server/src/storage/query.cpp

@@ -68,3 +68,41 @@ void Query::Condition::addCondition( const Condition &condition )

 {

   mSubConditions << condition;

 }

+

+

+Case::Case(const Condition &when, const QString &then, const QString &elseBranch)

+{

+    addCondition(when, then);

+    setElse(elseBranch);

+}

+

+Case::Case(const QString &column, CompareOperator op, const QVariant &value, const QString &when, const QString &elseBranch)

+{

+    addValueCondition(column, op, value, when);

+    setElse(elseBranch);

+}

+

+void Case::addCondition(const Condition &when, const QString &then)

+{

+    mWhenThen.append(qMakePair(when, then));

+}

+

+void Case::addValueCondition(const QString &column, CompareOperator op, const QVariant &value, const QString &then)

+{

+    Condition when;

+    when.addValueCondition(column, op, value);

+    addCondition(when, then);

+}

+

+void Case::addColumnCondition(const QString &column, CompareOperator op, const QString &column2, const QString &then)

+{

+    Condition when;

+    when.addColumnCondition(column, op, column2);

+    addCondition(when, then);

+}

+

+void Case::setElse(const QString &elseBranch)

+{

+    mElse = elseBranch;

+}

+

diff --git a/server/src/storage/query.h b/server/src/storage/query.h

index f4f1ac0..c8f35a7 100644

--- a/server/src/storage/query.h

+++ b/server/src/storage/query.h

@@ -130,6 +130,25 @@ class Condition

 }; // class Condition

+

+class Case

+{

+  friend class Akonadi::Server::QueryBuilder;

+  public:

+    Case(const Condition &when, const QString &then, const QString &elseBranch = QString());

+    Case(const QString &column, Query::CompareOperator op, const QVariant &value, const QString &when, const QString &elseBranch = QString());

+

+    void addCondition(const Condition &when, const QString &then;;

+    void addValueCondition(const QString &column, Query::CompareOperator op, const QVariant &value, const QString &then;;

+    void addColumnCondition(const QString &column, Query::CompareOperator op, const QString &column2, const QString &then;;

+

+    void setElse(const QString &elseBranch);

+

+  private:

+    QVector<QPair<Condition, QString> > mWhenThen;

+    QString mElse;

+};

+

 } // namespace Query

 } // namespace Server

 } // namespace Akonadi

diff --git a/server/src/storage/querybuilder.cpp b/server/src/storage/querybuilder.cpp

index 3017867..74ed2da 100644

--- a/server/src/storage/querybuilder.cpp

+++ b/server/src/storage/querybuilder.cpp

@@ -457,11 +457,27 @@ void QueryBuilder::addColumn( const QString &col )

   mColumns << col;

 }

+void QueryBuilder::addColumn( const Query::Case &caseStmt )

+{

+  QString query;

+  buildCaseStatement(&query, caseStmt);

+  mColumns.append(query);

+}

+

 void QueryBuilder::addAggregation( const QString &col, const QString &aggregate )

 {

   mColumns.append( aggregate + QLatin1Char( '(' ) + col + QLatin1Char( ')' ) );

 }

+void QueryBuilder::addAggregation(const Query::Case &caseStmt, const QString &aggregate)

+{

+  QString query(aggregate + QLatin1Char('('));

+  buildCaseStatement(&query, caseStmt);

+  query += QLatin1Char(')');

+

+  mColumns.append(query);

+}

+

 void QueryBuilder::bindValue( QString *query, const QVariant &value )

 {

   mBindValues << value;

@@ -510,6 +526,20 @@ void QueryBuilder::buildWhereCondition( QString *query, const Query::Condition &

   }

 }

+void QueryBuilder::buildCaseStatement(QString *query, const Query::Case &caseStmt)

+{

+    *query += QLatin1String("CASE ");

+    for (const auto whenThen : caseStmt.mWhenThen) {

+        *query += QLatin1String("WHEN ");

+        buildWhereCondition(query, whenThen.first);    // When

+        *query += QLatin1String(" THEN ") + whenThen.second; // then

+    }

+    if (!caseStmt.mElse.isEmpty()) {

+        *query += QLatin1String(" ELSE ") + caseStmt.mElse;

+    }

+    *query += QLatin1String(" END");

+}

+

 void QueryBuilder::setSubQueryMode( Query::LogicOperator op, ConditionType type )

 {

   Q_ASSERT( type == WhereCondition || ( type == HavingCondition && mType == Select ) );

diff --git a/server/src/storage/querybuilder.h b/server/src/storage/querybuilder.h

index df7c362..0304108 100644

--- a/server/src/storage/querybuilder.h

+++ b/server/src/storage/querybuilder.h

@@ -123,6 +123,12 @@ class QueryBuilder

     void addColumn( const QString &col );

     /**

+     * Adds the given case statement to a select query.

+     * @param caseStmt The case statement to add.

+     */

+    void addColumn( const Query::Case &caseStmt );

+

+    /**

      * Adds an aggregation statement.

      * @param col The column to aggregate on

      * @param aggregate The aggregation function.

@@ -130,6 +136,13 @@ class QueryBuilder

     void addAggregation( const QString &col, const QString &aggregate );

     /**

+     * Adds and aggregation statement with CASE

+     * @param caseStmt The case statement to aggregate on

+     * @param aggregate The aggregation function.

+     */

+    void addAggregation( const Query::Case &caseStmt, const QString &aggregate );

+

+    /**

       Add a WHERE or HAVING condition which compares a column with a given value.

       @param column The column that should be compared.

       @param op The operator used for comparison

@@ -239,6 +252,7 @@ class QueryBuilder

     void buildQuery( QString *query );

     void bindValue( QString *query, const QVariant &value );

     void buildWhereCondition( QString *query, const Query::Condition &cond );

+    void buildCaseStatement( QString *query, const Query::Case &caseStmt );

     /**

      * SQLite does not support JOINs with UPDATE, so we have to convert it into

diff --git a/server/tests/unittest/querybuildertest.cpp b/server/tests/unittest/querybuildertest.cpp

index 92df2a2..848829d 100644

--- a/server/tests/unittest/querybuildertest.cpp

+++ b/server/tests/unittest/querybuildertest.cpp

@@ -217,6 +217,42 @@ void QueryBuilderTest::testQueryBuilder_data()

   }

   {

+    /// SELECT with CASE

+    QueryBuilder qbTpl = QueryBuilder("table1", QueryBuilder::Select );

+    qbTpl.setDatabaseType( DbType::MySQL );

+

+    QueryBuilder qb = qbTpl;

+    qb.addColumn( "col" );

+    qb.addColumn( Query::Case( "col1", Query::Greater, 42, "1", "0" ) );

+    bindVals.clear();

+    bindVals << 42;

+    mBuilders << qb;

+    QTest::newRow( "select case simple") << mBuilders.count()

+        << QString( "SELECT col, CASE WHEN ( col1 > :0 ) THEN 1 ELSE 0 END FROM table1" ) << bindVals;

+

+

+    qb = qbTpl;

+    qb.addAggregation( "table1.col1", "sum" );

+    qb.addAggregation( "table1.col2", "count" );

+    Query::Condition cond( Query::Or );

+    cond.addValueCondition( "table3.col2", Query::Equals, "value1" );

+    cond.addValueCondition( "table3.col2", Query::Equals, "value2" );\

+    Query::Case caseStmt( cond, "1", "0" );

+    qb.addAggregation( caseStmt, "sum" );

+    qb.addJoin( QueryBuilder::LeftJoin, "table2", "table1.col3", "table2.col1" );

+    qb.addJoin( QueryBuilder::LeftJoin, "table3", "table2.col2", "table3.col1" );

+    bindVals.clear();

+    bindVals << QString("value1") << QString("value2");

+    mBuilders <

+    QTest::newRow( "select case, aggregation and joins" ) << mBuilders.count()

+        << QString( "SELECT sum(table1.col1), count(table1.col2), sum(CASE WHEN ( table3.col2 = :0 OR table3.col2 = :1 ) THEN 1 ELSE 0 END) "

+                    "FROM table1 "

+                    "LEFT JOIN table2 ON ( table1.col3 = table2.col1 ) "

+                    "LEFT JOIN table3 ON ( table2.col2 = table3.col1 )")

+        << bindVals;

+  }

+

+  {

     /// UPDATE with INNER JOIN

     QueryBuilder qbTpl = QueryBuilder( "table1", QueryBuilder::Update );

     qbTpl.setColumnValue( "col", 42 );

@@ -310,4 +346,4 @@ void QueryBuilderTest::benchQueryBuilder()

   }

   QVERIFY(executed);

-}

\ No newline at end of file

+}

-- 

2.1.0