Khurram Faraaz created DRILL-4944:
-------------------------------------

             Summary: incorrect results - case expression
                 Key: DRILL-4944
                 URL: https://issues.apache.org/jira/browse/DRILL-4944
             Project: Apache Drill
          Issue Type: Bug
          Components: Execution - Flow
    Affects Versions: 1.9.0
            Reporter: Khurram Faraaz
            Priority: Critical


Drill 1.9.0 (git commit id: 4edabe7a) returns null, which is wrong.
 {noformat}
 0: jdbc:drill:schema=dfs.tmp> SELECT res2, case res2 WHEN 0.1 THEN 0.9999 ELSE 
null END
. . . . . . . . . . . . . . > FROM
. . . . . . . . . . . . . . > (
. . . . . . . . . . . . . . >     SELECT
. . . . . . . . . . . . . . >     (CASE WHEN (false) THEN null ELSE CAST(0.1 as 
float) end) res2
. . . . . . . . . . . . . . >     FROM (values(1)) foo
. . . . . . . . . . . . . . > ) foobar ;
+-------+---------+
| res2  | EXPR$1  |
+-------+---------+
| 0.1   | null    |
+-------+---------+
1 row selected (0.106 seconds)
 {noformat}
 
 Postgres returns correct results
  {noformat}
 postgres=# SELECT res2, case res2 WHEN 0.1 THEN 0.9999 ELSE null END
postgres-# FROM
postgres-# (
postgres(#     SELECT
postgres(#     (CASE WHEN (false) THEN null ELSE CAST(0.1 as float) end) res2
postgres(#     FROM (values(1)) foo
postgres(# ) foobar ;
 res2 |  case
------+--------
  0.1 | 0.9999
(1 row)
 {noformat}
 
 Calcite also returns correct results
  {noformat}
 0: jdbc:calcite:model=target/test-classes/mod> SELECT res2, case res2 WHEN 0.1 
THEN 0.9999 ELSE null END
. . . . . . . . . . . . . . . . . . . . . . .> FROM
. . . . . . . . . . . . . . . . . . . . . . .> (
. . . . . . . . . . . . . . . . . . . . . . .>       SELECT
. . . . . . . . . . . . . . . . . . . . . . .>          (CASE WHEN (false) THEN 
null ELSE CAST(0.1 as float) end) res2
. . . . . . . . . . . . . . . . . . . . . . .>      FROM (values(1)) foo
. . . . . . . . . . . . . . . . . . . . . . .> ) foobar ;
+-----------------+--------+
|      RES2       | EXPR$1 |
+-----------------+--------+
| 0.1             | 0.9999 |
+-----------------+--------+
1 row selected (1.277 seconds)
 {noformat}
 
 Details of explain plan from Drill 1.9.0
  {noformat}
 0: jdbc:drill:schema=dfs.tmp> explain plan for SELECT res2, case res2 WHEN 0.1 
THEN 0.9999 ELSE null END
. . . . . . . . . . . . . . > FROM
. . . . . . . . . . . . . . > (
. . . . . . . . . . . . . . >       SELECT
. . . . . . . . . . . . . . >          (CASE WHEN (false) THEN null ELSE 
CAST(0.1 as float) end) res2
. . . . . . . . . . . . . . >      FROM (values(1)) foo
. . . . . . . . . . . . . . > ) foobar ;
+------+------+
| text | json |
+------+------+
| 00-00    Screen
00-01      Project(res2=[$0], EXPR$1=[$1])
00-02        Project(res2=[CASE(false, null, 0.1)], EXPR$1=[CASE(=(CASE(false, 
null, 0.1), 0.1), 0.9999, null)])
00-03          Values
 | {
  "head" : {
    "version" : 1,
    "generator" : {
      "type" : "ExplainHandler",
      "info" : ""
    },
    "type" : "APACHE_DRILL_PHYSICAL",
    "options" : [ ],
    "queue" : 0,
    "resultMode" : "EXEC"
  },
  "graph" : [ {
    "pop" : "Values",
    "@id" : 3,
    "content" : [ {
      "EXPR$0" : {
        "$numberLong" : 1
      }
    } ],
    "initialAllocation" : 1000000,
    "maxAllocation" : 10000000000,
    "cost" : 1.0
  }, {
    "pop" : "project",
    "@id" : 2,
    "exprs" : [ {
      "ref" : "`res2`",
      "expr" : " ( if (false ) then (NULL )  else (0.1 )  end  ) "
    }, {
      "ref" : "`EXPR$1`",
      "expr" : " ( if (equal( ( if (false ) then (NULL )  else (0.1 )  end  ) , 
0.1)  ) then (0.9999 )  else (NULL )  end  ) "
    } ],
    "child" : 3,
    "initialAllocation" : 1000000,
    "maxAllocation" : 10000000000,
    "cost" : 1.0
  }, {
    "pop" : "project",
    "@id" : 1,
    "exprs" : [ {
      "ref" : "`res2`",
      "expr" : "`res2`"
    }, {
      "ref" : "`EXPR$1`",
      "expr" : "`EXPR$1`"
    } ],
    "child" : 2,
    "initialAllocation" : 1000000,
    "maxAllocation" : 10000000000,
    "cost" : 1.0
  }, {
    "pop" : "screen",
    "@id" : 0,
    "child" : 1,
    "initialAllocation" : 1000000,
    "maxAllocation" : 10000000000,
    "cost" : 1.0
  } ]
} |
 {noformat}



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