Exception while executing search

[mfaulcon-mynexus]

I have a CachedUser class (defined below) for which I'm trying to execute a string.contains query on one of the member fields, during which I'm getting an exception. I've listed the code and runtime values below. If I perform straight equality searches, it appears to work correctly.

CachedUser.cs

[Document(StorageType = StorageType.Json, Prefixes = [Prefix], IndexName = Prefix + ":idx")]
public class CachedUser : IEntity<Guid>
{
    public const string Prefix = "graph3:user";

    [Indexed(Sortable = true, IndexEmptyAndMissing = false)]
    [RedisIdField]
    public Guid UserId { get; set; }

    [Indexed(IndexEmptyAndMissing = false)]
    public string? Email { get; set; }

    [Indexed(Sortable = true, IndexEmptyAndMissing = false)]
    public string? FirstName { get; set; }

    [Searchable(Sortable = true, IndexEmptyAndMissing = false)]
    public string? LastName { get; set; }

    [Indexed(Sortable = true, IndexEmptyAndMissing = false)]
    public string? DisplayName { get; set; }

    [Indexed(IndexEmptyAndMissing = false)]
    public string? Credentials { get; set; }

    // Irrelevant properties removed

    [JsonIgnore]
    public Guid Id => UserId;
}

The Index being created (formatted for readability):

FT.CREATE graph3:user:idx ON Json PREFIX 1 graph3:user SCHEMA 
  $.UserId AS UserId TAG SEPARATOR | SORTABLE
  $.Email AS Email TAG SEPARATOR |
  $.FirstName AS FirstName TAG SEPARATOR | SORTABLE
  $.LastName AS LastName TEXT SORTABLE
  $.DisplayName AS DisplayName TAG SEPARATOR | SORTABLE
  $.Credentials AS Credentials TAG SEPARATOR |

The expression being executed at runtime:

.Where(u => u.contains("Fal"))
.Select(cu => new CachedUser()
{
  UserId = cu.UserId,
  Email = cu.Email,
  FirstName = cu.FirstName,
  LastName = cu.LastName,
  DisplayName = cu.DisplayName
})
.Take(11);

The Redis search the expression is being translated to:

FT.SEARCH graph3:user:idx ((ismissing(@LastName)) (@LastName:Fal)) DIALECT 2 LIMIT 0 11 RETURN 21 UserId AS UserId Email AS Email FirstName AS FirstName LastName AS LastName DisplayName AS DisplayName

The exception being thrown:

StackExchange.Redis.RedisServerException:Syntax error at offset 21 near LastName
   at Redis.OM.RedisConnection.ExecuteAsync(String command, Object[] args) in \Redis.OM\src\Redis.OM\RedisConnection.cs:line 45

When I execute the same command from the CLI, I get the error: "Unknown argument (@LastName:Fal)) at position 2 for

"

[slorello89]

Hi @mfaulcon-mynexus - that's really strange, it should only call ismissing if you are checking for nullness in your query - are you sure you aren't? I'm trying to replicate this and my machine and it seems to be working fine.

I'm not convinced I'm seeing the full picture of your query here:

.Where(u => u.contains("Fal"))
.Select(cu => new CachedUser()
{
  UserId = cu.UserId,
  Email = cu.Email,
  FirstName = cu.FirstName,
  LastName = cu.LastName,
  DisplayName = cu.DisplayName
})
.Take(11);

doesn't make much sense in context - as I would think u would be a CachedUser that doesn't seem to have a contains method?

[mfaulcon-mynexus]

@slorello89 - Apologies, I translated the expression tree back into Linq, and I missed a term. It should be:

.Where(u => u.LastName.contains("Fal"))
.Select(cu => new CachedUser()
{
  UserId = cu.UserId,
  Email = cu.Email,
  FirstName = cu.FirstName,
  LastName = cu.LastName,
  DisplayName = cu.DisplayName
})
.Take(11);

The expression tree is coming from the Enumerator of a GraphQL query, so not one I’m constructing directly.

[slorello89]

perhaps that's it - because that query would be consistent with u.LastName == null && u.LastName.contains("Fal") - which obviously doesn't make much sense 🤔 what's the graphql you are using?

[mfaulcon-mynexus]

HotChocolate 15.x

[mfaulcon-mynexus]

@slorello89 - I took another look at the expression tree, and HotChocolate is doing a null check; the revised where statement would be .Where(u => u.LastName != null && u.LastName.contains("Fal"). I've included the entire expression tree below:

.Call System.Linq.Queryable.Take(
    .Call System.Linq.Queryable.Select(
        .Call System.Linq.Queryable.Where(
            .Constant<Redis.OM.Searching.RedisCollection`1[Graph.Domain.Caching.Users.CachedUser]>(Redis.OM.Searching.RedisCollection`1[Graph.Domain.Caching.Users.CachedUser]),
            '(.Lambda #Lambda1<System.Func`2[Graph.Domain.Caching.Users.CachedUser,System.Boolean]>)),
        '(.Lambda #Lambda2<System.Func`2[Graph.Domain.Caching.Users.CachedUser,Graph.Domain.Caching.Users.CachedUser]>)),
    11)

.Lambda #Lambda1<System.Func`2[Graph.Domain.Caching.Users.CachedUser,System.Boolean]>(Graph.Domain.Caching.Users.CachedUser $_s0)
{
    $_s0.LastName != null && .Call ($_s0.LastName).Contains(.Constant<HotChocolate.Data.Filters.Expressions.FilterExpressionBuilder+ExpressionParameter`1[System.String]>(ExpressionParameter { p = Fal }).p)
}

.Lambda #Lambda2<System.Func`2[Graph.Domain.Caching.Users.CachedUser,Graph.Domain.Caching.Users.CachedUser]>(Graph.Domain.Caching.Users.CachedUser $_s1)
{
    .New Graph.Domain.Caching.Users.CachedUser(){
        UserId = $_s1.UserId,
        Email = $_s1.Email,
        FirstName = $_s1.FirstName,
        LastName = $_s1.LastName,
        DisplayName = $_s1.DisplayName
    }
}

Does this have anything to do with my CachedUser class having IndexEmptyAndMissing = false in the Searchable attribute?

[slorello89]

Ok, that makes a lot more sense - what version of RediSearch are you using?

[mfaulcon-mynexus]

@slorello89 - I'm using Azure Redis Enterprise. The results of running MODULE LIST is below:

1) 1) "name"
   2) "search"
   3) "ver"
   4) "20819"
   5) "path"
   6) "/enterprise-managed"
   7) "args"
   8) 1) "PARTITIONS"
      2) "AUTO"
2) 1) "name"
   2) "ReJSON"
   3) "ver"
   4) "20613"
   5) "path"
   6) "/enterprise-managed"
   7) "args"
   8) (empty list or set)

[slorello89]

I believe the null Query stuff was introduced in 2.10 - so it needs another upgrade to work. The == null would have been an invalid operation exception before IIRC so the issue is the null check created by the graphql provider - you might be able to get RediSearch updated if you contact Azure support.

[mfaulcon-mynexus]

@slorello89 - I've submitted the ticket. In the mean time, I'm testing with an instance of Azure Managed Redis, which has newer Redis modules:

1) 1) "name"
   2) "timeseries"
   3) "ver"
   4) "11205"
   5) "path"
   6) "/enterprise-managed"
   7) "args"
   8) (empty list or set)
2) 1) "name"
   2) "search"
   3) "ver"
   4) "21017"
   5) "path"
   6) "/enterprise-managed"
   7) "args"
   8) (empty list or set)
3) 1) "name"
   2) "bf"
   3) "ver"
   4) "20806"
   5) "path"
   6) "/enterprise-managed"
   7) "args"
   8) (empty list or set)
4) 1) "name"
   2) "ReJSON"
   3) "ver"
   4) "20808"
   5) "path"
   6) "/enterprise-managed"
   7) "args"
   8) (empty list or set)

Using this instance of Redis, I was able to get past the problem. I did have to switch my Searchable attribute to IndexEmptyAndMissing = true to get past another problem, but when I did, I started getting this exception:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Redis.OM.Common.ExpressionParserUtilities.ValueToString(Object value) in \Redis.OM\src\Redis.OM\Common\ExpressionParserUtilities.cs:line 1036
Call Stack:
   Redis.OM.dll!Redis.OM.Common.ExpressionParserUtilities.ValueToString(object value) Line 1036
   Redis.OM.dll!Redis.OM.Common.ExpressionParserUtilities.GetOperandString(System.Linq.Expressions.Expression exp, bool filterFormat) Line 44
   Redis.OM.dll!Redis.OM.Aggregation.AggregationPredicates.QueryPredicate.ValidateAndPushOperand(System.Linq.Expressions.Expression expression, System.Collections.Generic.Stack<string> stack) Line 61
   Redis.OM.dll!Redis.OM.Aggregation.AggregationPredicates.QueryPredicate.SplitBinaryExpression(System.Linq.Expressions.BinaryExpression expression, System.Collections.Generic.Stack<string> stack) Line 169
   Redis.OM.dll!Redis.OM.Aggregation.AggregationPredicates.QueryPredicate.SplitBinaryExpression(System.Linq.Expressions.BinaryExpression expression, System.Collections.Generic.Stack<string> stack) Line 155
   Redis.OM.dll!Redis.OM.Common.BooleanExpression.SplitExpression() Line 48
   Redis.OM.dll!Redis.OM.Aggregation.AggregationPredicates.QueryPredicate.Serialize() Line 36
   Redis.OM.dll!Redis.OM.Aggregation.RedisAggregation.Serialize() Line 67
   Redis.OM.dll!Redis.OM.Searching.RedisQueryProvider.ExecuteReductiveAggregation(System.Linq.Expressions.MethodCallExpression expression, System.Type underpinningType) Line 213
   Redis.OM.dll!Redis.OM.Searching.RedisQueryProvider.Execute<int>(System.Linq.Expressions.Expression expression) Line 282

Do I have something configured incorrectly?

[mfaulcon-mynexus]

@slorello89 - Also, shouldn't the u => u.LastName != null clause in the Linq expression have been translated to (-ismissing(@LastName)) instead of (ismissing(@LastName))?

[mfaulcon-mynexus]

I haven't tested it extensively, but I think the modification to Redis.OM.Common.ExpressionTranslator, line 418 below fixes the negation problem:

-                    return $"(ismissing({leftContent}))";
+                    return binExpression.NodeType switch
+                    {
+                        ExpressionType.Equal => $"(ismissing({leftContent}))",
+                        ExpressionType.NotEqual => $"-(ismissing({leftContent}))",
+                        _ => throw new ArgumentException($"The expression node type {binExpression.NodeType} is not supported"),
+                    };

[mfaulcon-mynexus]

@slorello89 - I was also able to address the NullReferenceException by making the modification below to Redis.OM.Common.ExpressionParserUtilities, line 1036:

        private static string ValueToString(object value)
        {
+            if (value is null)
+            {
+                return "null";
+            }
+
            Type valueType = value.GetType();

I think this may also address #514, as well.