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https://issues.apache.org/jira/browse/DRILL-4944?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15622344#comment-15622344
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Serhii Harnyk commented on DRILL-4944:
--------------------------------------
Result of SELECT 0.1 FROM (values(1)) where 1=1
1 row(s):
-----------------------------------------------------
| EXPR$0<FLOAT8(REQUIRED)>
-----------------------------------------------------
| 0.1
-----------------------------------------------------
Result of SELECT CAST(0.1 as float) FROM (values(1)) where 1=1
-----------------------------------------------------
| EXPR$0<FLOAT4(REQUIRED)> |
-----------------------------------------------------
| 0.1 |
-----------------------------------------------------
As you can see default type for 0.1 is FLOAT8 - "double", not "float".
So the query like SELECT 1 FROM (values(1)) where 0.1 = CAST(0.1 as float)
will have a result:
0 row(s):
Total record count: 0
The problem is that Drill when does comparison considers type of argument, not
only value. So we need to decide - is it bug or feature.
There are two ways for fixing this "bug".
1. Set default type floats - float4.
2. Don't consider type in comparisons.
Both ways can cause huge effects for the system.
> 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
> Assignee: Serhii Harnyk
> Priority: Critical
> Fix For: 1.9.0
>
>
> 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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