Unexpected behavior of ARRAY_SLICE in Cosmos Db SQL API - sql

Question

I have Cosmos DB collection (called sample) containing the following documents:
[
{
"id": "id1",
"messages": [
{
"messageId": "message1",
"Text": "Value1"
},
{
"messageId": "message2",
"Text": "Value2"
}
]
},
{
"id": "id2",
"messages": [
{
"messageId": "message3",
"Text": "Value3"
},
{
"messageId": "message4",
"Text": "Value1"
}
]
},
{
"id": "id3",
"messages": [
{
"messageId": "message5",
"Text": "Value1"
},
{
"messageId": "message6",
"Text": "Value2"
}
]
},
{
"id": "id4",
"messages": [
{
"messageId": "message7",
"Text": "Value5"
},
{
"messageId": "message8",
"Text": "Value2"
}
]
},
]
I am trying to retrieve all the Documents, having messages and the first message has the field "Text"= 'Value1'.
In this sample the documents with the ids '1' and '3' would be retrieved. Please notice that the document with id='id2' wouldn't be retrieved,
since the value of the text of the first message is 'Value3'.
The collection as mentioned is called sample and I am running the following Query:
"select sample.id, sample.messages, ARRAY_SLICE(sample.messages, 0, 1)[0].Text as valueOfText from sample"
As you can see in the first two images, I retrieve all Documents and every one of them have the field "valueOfText" set to value of the first message, as expected.
Now when I filter the collection (the third image), I retrieve no results at all.
Is this an expected behavior?

Answer 1

Following your sql, got same results:
But why you have to use ARRAY_SLICE,it is used to return truncated array.Since your requirement is specific:
trying to retrieve all the Documents, having messages and the first
message has the field "Text"= 'Value1'
Just use sql:
SELECT c.id,c.messages,c.messages[0].Text as valueOfText FROM c
where c.messages[0].Text = 'Value1'
Output: