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https://issues.apache.org/jira/browse/DRILL-5419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15998269#comment-15998269
]
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_r113915317
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillOptiq.java
---
@@ -599,10 +598,28 @@ public LogicalExpression visitLiteral(RexLiteral
literal) {
throw new UnsupportedOperationException(String.format("Unable to
convert the value of %s and type %s to a Drill constant expression.", literal,
literal.getType().getSqlTypeName()));
}
}
- }
- private static final TypedNullConstant createNullExpr(MinorType type) {
- return new TypedNullConstant(Types.optional(type));
+ /**
+ * Create nullable major type using given minor type
+ * and wraps it in typed null constant.
+ *
+ * @param type minor type
+ * @return typed null constant instance
+ */
+ private TypedNullConstant createNullExpr(MinorType type) {
+ return new TypedNullConstant(Types.optional(type));
+ }
+
+ /**
+ * Create nullable varchar major type with given precision
+ * and wraps it in typed null constant.
+ *
+ * @param precision precision value
+ * @return typed null constant instance
+ */
+ private TypedNullConstant createStringNullExpr(int precision) {
+ return new TypedNullConstant(Types.withPrecision(MinorType.VARCHAR,
TypeProtos.DataMode.OPTIONAL, precision));
--- End diff --
4. Expanded reply in previous comment.
> 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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