Check if row contains a nested item in DynamoDB? - sql

Question

I am trying to use PartiQL with DynamoDB to perform SQL queries to check if a device is inactive and contains an error. Here's is the query I am using:
SELECT *
FROM "table"
WHERE "device"."active" = 0 AND "device"."error" IS NOT NULL
However I've noticed that even if a device doesn't have the error item, the query still returns a row. How can I query a device that only contains the error item?
With error item
{
"id": "value",
"name": "value,
"device": {
"active": 0,
"error": {
"reason": "value"
}
}
}
Without error item
{
"id": "value",
"name": "value,
"device": {
"active": 0
}
}

Answer 1

You're looking for IS NOT MISSING :) That's the partiql version of the filter expression operator function attribute_exists.
Given a table with a primary key PK, sort key SK, and the following data:
PK
SK
myMap
foo
1
{}
foo
2
{"test": {}}
-- Returns both foo 1 and foo 2
SELECT *
FROM "my-table"
WHERE "PK" = 'foo' AND "myMap"."test" IS NOT NULL
-- Returns just foo 2
SELECT *
FROM "my-table"
WHERE "PK" = 'foo' AND "myMap"."test" IS NOT MISSING
Also made sure my example specifies the PK in the WHERE clause - otherwise, your query will be a full scan. Maybe that's what you want, though. Just something to be aware of.