/// <summary>
/// Builds a query plan.
/// </summary>
/// <param name="messages">
/// The messages.
/// </param>
/// <param name="data">
/// The data.
/// </param>
/// <param name="node">
/// The script.
/// </param>
/// <returns>
/// The <see cref="Task"/>.
/// </returns>
public static IQueryPlan Build(IMessageWriter messages, INodeDataProvider data, Node node)
{
var generator = new QueryPlanBuilder(messages, data);
generator.Visit(node);
return(data.GetQueryPlan(node));
}
protected internal override Node VisitSelectSource(SelectSource node)
{
node = (SelectSource)base.VisitSelectSource(node);
var selectQuery = QueryPlanBuilder.Build(this.messages, this.data, node.Select);
var aliases = new HashSet <string>(
new[]
{
node.Alias,
});
var factory = Expression.New(
typeof(SelectDataSource).GetTypeInfo().DeclaredConstructors.First(),
Expression.Constant(selectQuery),
Expression.Constant(aliases));
this.data.SetFactoryExpression(node, factory);
return(node);
}
/// <summary>
/// Gets a function that creates the values for the selected records from a row.
/// </summary>
/// <param name="expressions">
/// The <see cref="AliasedSqlExpression"/>s to get the values for.
/// </param>
/// <param name="fieldList">
/// A collection that will be filled with all the fields that are used in the select statement.
/// </param>
/// <param name="wildCardAliasList">
/// A collection that will be filled with all the wildcards that are used in the select statement.
/// </param>
/// <param name="allSourceAliases">
/// Contains all source aliases in the query, so when a global wildcard is found, all fields are added.
/// </param>
/// <returns>
/// A delegate.
/// </returns>
private Delegate GetValueFactory([NotNull] IEnumerable <AliasedSqlExpression> expressions, ICollection <IField> fieldList, ICollection <string> wildCardAliasList, IEnumerable <string> allSourceAliases)
{
var row = Expression.Parameter(typeof(Row), "row");
var context = Expression.Parameter(typeof(IExecutionContext), "context");
var fieldFactories = new List <LambdaExpression>();
var lambdaVisitor = new GenericVisitor
{
(ExecutionContextExpression e) => context,
(SourceFieldExpression e) =>
{
fieldList?.Add(new Field(e.SourceName, e.FieldName));
return(e.CreateGetter(row));
},
(UnaryExpression e) => e.NodeType == ExpressionType.Convert ? (e.Operand as SourceFieldExpression)?.CreateGetter(row, e.Type) : null,
};
Func <string, Expression, Expression <Func <IExecutionContext, Row, KeyValuePair <string, object> > > > convertToLambda = (alias, expression) =>
{
var lambda = lambdaVisitor.Visit(expression.EvaluateAsValue());
lambda = lambda.Type == typeof(object) ? lambda : Expression.Convert(lambda, typeof(object));
return(Expression.Lambda <Func <IExecutionContext, Row, KeyValuePair <string, object> > >(Expression.New(QueryPlanBuilder.KeyValuePairConstructor, Expression.Constant(alias), lambda.CatchErrors()), context, row));
};
Expression <ValueFactory> result = null;
var wildcardIndex = 0;
var hasGlobalAlias = false;
foreach (var expression in expressions)
{
if (expression.Expression is WildcardSqlExpression wildcard)
{
if (wildcard.Source != null)
{
wildCardAliasList.Add(wildcard.Source);
}
else
{
hasGlobalAlias = true;
}
var sourcePrefix = $"{wildcard.Source}.";
var index = wildcardIndex++;
var lambda = string.IsNullOrEmpty(wildcard.Source)
? (Expression <ValueFactory>)((c, r) => r.ColumnNames.Select(cn => new KeyValuePair <string, object>($"{index}!{cn}", r[cn])))
: (c, r) => r.ColumnNames.Where(cn => cn.StartsWith(sourcePrefix)).Select(cn => new KeyValuePair <string, object>($"{index}!{cn}", r[cn]));
lambda = lambda.ReplaceParameter(lambda.Parameters[0], context).ReplaceParameter(lambda.Parameters[1], row);
if (fieldFactories.Count != 0)
{
var fields = QueryPlanBuilder.ToArrayInit <ValueFactory>(fieldFactories);
result = result == null ? fields : QueryPlanBuilder.ConcatenateLambdas(result, fields);
fieldFactories.Clear();
}
result = result == null ? lambda : QueryPlanBuilder.ConcatenateLambdas(result, lambda);
}
else
{
fieldFactories.Add(convertToLambda(expression.Alias, this.data.ConvertToLinqExpression(expression.Expression)));
}
}
if (fieldFactories.Count != 0)
{
var fields = QueryPlanBuilder.ToArrayInit <ValueFactory>(fieldFactories);
result = result == null ? fields : QueryPlanBuilder.ConcatenateLambdas(result, fields);
}
if (hasGlobalAlias)
{
foreach (var alias in allSourceAliases)
{
wildCardAliasList.Add(alias);
}
}
var asyncResult = (result ?? ((c, r) => Enumerable.Empty <KeyValuePair <string, object> >())).RewriteTasksToAsyncExpression();
return(asyncResult.ReturnType == typeof(IEnumerable <KeyValuePair <string, object> >)
? ((Expression <ValueFactory>)asyncResult).Compile()
: (Delegate)((Expression <AsyncValueFactory>)asyncResult).Compile());
}