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https://issues.apache.org/jira/browse/DRILL-5419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15998254#comment-15998254
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ASF GitHub Bot commented on DRILL-5419:
---------------------------------------
Github user arina-ielchiieva commented on a diff in the pull request:
https://github.com/apache/drill/pull/819#discussion_r113915026
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillOptiq.java
---
@@ -512,9 +511,9 @@ public LogicalExpression visitLiteral(RexLiteral
literal) {
return ValueExpressions.getBit(((Boolean) literal.getValue()));
case CHAR:
if (isLiteralNull(literal)) {
- return createNullExpr(MinorType.VARCHAR);
+ return createStringNullExpr(literal.getType().getPrecision());
--- End diff --
The length is 4, we treat it as regular string. If customer wants to treat
such literals as actual null value, then he needs to handle such case in sql
code. For example, `select case when col = 'NULL' then cast(null as varchar(10)
else col end from t`. Converting 'NULL' string to null value implicitly may not
be a good idea, since we don't know how users wants us to treat such literals.
I think it's ok if user will handle such cases by himself.
> Calculate return string length for literals & some string functions
> -------------------------------------------------------------------
>
> Key: DRILL-5419
> URL: https://issues.apache.org/jira/browse/DRILL-5419
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.9.0
> Reporter: Arina Ielchiieva
> Assignee: Arina Ielchiieva
> Attachments: version_with_cast.JPG
>
>
> Though Drill is schema-less and cannot determine in advance what the length
> of the column should be but if query has an explicit type/length specified,
> Drill should return correct column length.
> For example, JDBC / ODBC Driver is ALWAYS returning 64K as the length of a
> varchar or char even if casts are applied.
> Changes:
> *LITERALS*
> String literals length is the same as actual literal length.
> Example: for 'aaa' return length is 3.
> *CAST*
> Return length is the one indicated in cast expression. This also applies when
> user has created view where each string columns was casted to varchar with
> some specific length.
> This length will be returned to the user without need to apply cast one more
> time. Below mentioned functions can take leverage of underlying varchar
> length and calculate return length.
> *LOWER, UPPER, INITCAP, REVERSE, FIRST_VALUE, LAST_VALUE*
> Return length is underlying column length, i.e. if column is known, the same
> length will be returned.
> Example:
> lower(cast(col as varchar(30))) will return 30.
> lower(col) will return max varchar length, since we don't know actual column
> length.
> *LAG, LEAD*
> Return length is underlying column length but column type will be nullable.
> *LPAD, RPAD*
> Pads the string to the length specified. Return length is this specified
> length.
> *CONCAT, CONCAT OPERATOR (||)*
> Return length is sum of underlying columns length. If length is greater then
> varchar max length, varchar max length is returned.
> *IF EXPRESSIONS (CASE STATEMENT, COALESCE), UNION OPERATOR*
> When combining string columns with different length, return length is max
> from source columns.
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