public static Variable SetVariable(this IContext context, string variableName, SqlExpression value)
{
var currentContext = context;
while (currentContext != null) {
if (currentContext is IVariableScope) {
var scope = (IVariableScope) currentContext;
if (scope.HasVariable(variableName)) {
// TODO: support also in-context evaluation
var constantValue = value.EvaluateToConstant(null, context.VariableResolver());
return scope.SetVariable(variableName, constantValue);
}
}
currentContext = currentContext.Parent;
}
currentContext = context;
while (currentContext != null) {
if (currentContext is IVariableScope) {
var scope = (IVariableScope)currentContext;
// TODO: support also in-context evaluation
var constantValue = value.EvaluateToConstant(null, context.VariableResolver());
return scope.SetVariable(variableName, constantValue);
}
currentContext = currentContext.Parent;
}
// not found in the hierarchy
return null;
}
public static Field EvaluateToConstant(this SqlExpression expression, IRequest request, IVariableResolver variableResolver)
{
return(expression.EvaluateToConstant(new EvaluateContext(request, variableResolver)));
}
public static ITable Select(this ITable table, IQueryContext context, SqlExpression expression)
{
if (expression is SqlBinaryExpression) {
var binary = (SqlBinaryExpression)expression;
// Perform the pattern search expression on the table.
// Split the expression,
var leftRef = binary.Left.AsReferenceName();
if (leftRef != null)
// LHS is a simple variable so do a simple select
return table.SimpleSelect(context, leftRef, binary.ExpressionType, binary.Right);
}
// LHS must be a constant so we can just evaluate the expression
// and see if we get true, false, null, etc.
var v = expression.EvaluateToConstant(context, null);
// If it evaluates to NULL or FALSE then return an empty set
if (v.IsNull || v == false)
return table.EmptySelect();
return table;
}
