Filtering records with map bins using expressions

Client Libraries Java Client
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1

Hello,

I am using scanAll to filter records with a scan policy that contains a filter expression.

My data looks like the following:

{
   "PK":"somePrimaryKey",
   "someBinName":{
      "key1":{
         "fields":{
            "a":true,
            ...
         }
      },
      "key2":{
         "fields":{
            "a":false,
            ...
         }
      },
    ...
}

I am currently using the following expression:

Exp.build(
    Exp.eq(
        MapExp.getByKey(MapReturnType.VALUE, Exp.Type.BOOL, Exp.val("a"), Exp.mapBin("someBinName"), CTX.mapKey(Value.WILDCARD), CTX.mapKey(Value.get("fields"))), Exp.val(true)),
  )
)

What I am trying to do is, find all records that contain a key within the bin someBinName that contains a key by the name of fields, which within it contains a key by the name of a with the value true. So it’s basically sort of an OR expression, if I see a nested key a with the value true within ANY of the top level keys, I want to retrieve this record. I am using Value.WILDCARD because the top level keys (key1, key2, etc) are dynamic.

Assuming I have had the following structure for my data:

{
   "PK":"somePrimaryKey",
   "someBinName":{
      "key1":{
         "fields":{
            "a":true,
            ...
         }
      }
}

The query will work just fine, and return all records that contain the keys and true value as described above, however if an additional key is added to the bin like so:

{
   "PK":"somePrimaryKey",
   "someBinName":{
      "key1":{
         "fields":{
            "a":true,
            ...
         }
      },
      "key2":{
         "fields":{
            "a":false,
            ...
         }
      }
}

Then the query may not pick up this record, even though it does contain some key, which within it there’s a map with the key fields which within it there is a key by the name of a with the value true, in this case it would be key1. What I noticed is that when using Value.WILDCARD it picks a single key within the bin and executes the expression on that key alone, and the key that will be picked is the key which was most recently added/updated. So if I added key2 AFTER I added key1 the expression will not return my desired records, however if I added key1 AFTER key2 then it will return the records.

I guess I am probably using it wrong, even though it made sense to me that Value.WILDCARD will descent down all possible keys in the bin.

I had a good look at the documentation and the tutorial notebooks but I didn’t find anything that’s similar to my use case. Would appreciate if anyone can give me some insight on how I could build the expression such that it will return records as I described above, thank you.

2

Unfortunately, there is no current expression that can match all map keys. WILDCARD will not work in this case. The only way to navigate all map keys and filter on the server side is to use a UDF.