DistinctEnumerator.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Threading.Tasks;
using Waher.Script.Model;
 
namespace Waher.Script.Persistence.SQL.Enumerators
{
    public class DistinctEnumerator : RecordEnumerator
    {
        private readonly Dictionary<Record, bool> reported = new Dictionary<Record, bool>();
 
        public DistinctEnumerator(IResultSetEnumerator ItemEnumerator, ScriptNode[] Columns, Variables Variables)
            : base(ItemEnumerator, Columns, Variables)
        {
        }
 
        public override bool MoveNext()
        {
            while (base.MoveNext())
            {
                Record Rec = new Record(this.CurrentRecord);
                if (!this.reported.ContainsKey(Rec))
                {
                    this.reported[Rec] = true;
                    return true;
                }
            }
 
            return false;
        }
 
        public override async Task<bool> MoveNextAsync()
        {
            while (await base.MoveNextAsync())
            {
                Record Rec = new Record(this.CurrentRecord);
                if (!this.reported.ContainsKey(Rec))
                {
                    this.reported[Rec] = true;
                    return true;
                }
            }
 
            return false;
        }
 
        public override void Reset()
        {
            base.Reset();
            this.reported.Clear();
        }
 
    }
}