[ASTERIXDB-1212] Close-type list doesn't handle NULL well

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: *DB - AsterixDB, TYPE - Data Model
• Assignee: Yingyi Bu
• Reporter: Jianfeng Jia
• Created: 03/Dec/15 00:29
• Updated: 05/Jun/16 06:39
• Resolved: 05/Jun/16 06:39

Description

First, I observed the out of range access for the closed-type list and open-type list are quite different:

// closed type:
let $all := [ { "ka":"a1",  "kb":"b1"}, 
                 { "ka":"a2",  "kb":"b2"}]
return $all[3].ka

It returns a "", I think it should be null.
If I change the type to a hytogenous type like below

// open type:
let $all := [ { "ka":"a1",  "kb":"b1"}, 
                 { "ka":2,  "kb":"b2"}]
return $all[3].ka

It returns a null as expected.

Furthermore, the closed-type will return the wrong result by just access field by index other than by name. Here is example

let $all := [ { "ka":"a1",  "kb":"b1"}, 
                   { "ka":"a2",  "kb":"b2"}]
for $x in $all
group by $k := $x.kb with $x
return { "g": $k, "s1": $x[1].ka}

It returns

{ "g": "b1", "s1": "b1" }
{ "g": "b2", "s1": "b2" }

It seems it skipped some offset directly without verify if the record is null or not.

The open type doesn't have this problem. The following code

let $all := [ { "ka":"a1",  "kb":"b1"}, 
                   { "ka":2,  "kb":"b2"}]  // change ka to 2 to make a heterogenous type list
for $x in $all
group by $k := $x.kb with $x
return { "g": $k, "s1": $x[1].ka}

will always return

{ "g": "b1", "s1": null }
{ "g": "b2", "s1": null }

Issue Links

• is duplicated by: ASTERIXDB-905 Wrong results are returned upon asking for an item which doesn't exist