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https://issues.apache.org/jira/browse/IMPALA-7739?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Work on IMPALA-7739 started by Alex Rodoni.
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> Errata in documentation of decode() method
> ------------------------------------------
>
> Key: IMPALA-7739
> URL: https://issues.apache.org/jira/browse/IMPALA-7739
> Project: IMPALA
> Issue Type: Improvement
> Components: Docs
> Affects Versions: Impala 3.0
> Reporter: Paul Rogers
> Assignee: Alex Rodoni
> Priority: Minor
>
> Consider the description of {{decode()}} in [the
> docs|https://impala.apache.org/docs/build3x/html/topics/impala_conditional_functions.html].
> Original text:
> {quote}
> decode(type expression, type search1, type result1 [, type search2, type
> result2 ...] [, type default] )
> Purpose: Compares an expression to one or more possible values, and returns a
> corresponding result when a match is found.
> Return type: same as the initial argument value, except that integer values
> are promoted to BIGINT and floating-point values are promoted to DOUBLE; use
> CAST() when inserting into a smaller numeric column
> Usage notes:
> * Can be used as shorthand for a CASE expression.
> * The original expression and the search expressions must of the same type or
> convertible types. * The result expression can be a different type, but all
> result expressions must be of the same type.
> * Returns a successful match If the original expression is NULL and a search
> expression is also NULL. the
> * Returns NULL if the final default value is omitted and none of the search
> expressions match the original expression.
> {quote}
> Revise:
> * Remove “type” prefix for arguments (here and in all functions), it really
> adds no value and is actually confusing because the argument is not a type,
> it is a value.
> * Usage notes: Comparison is done using the IS NOT DISTINCT (<=>) operator:
> this NULL can be used as a search condition.
> * Since this is a list, great between the two items in the second item in
> usage.
> * The third item has a dangling “the” at the end.
> * Reword the fourth item: “If none of the search expressions match the
> expression, then returns the default (if given) or NULL (if no default is
> given.)”
> Suggested revised text:
> Purpose: Compares an expression to one or more possible values using the IS
> NOT DISTINCT operator, and returns a corresponding result when a match is
> found.
> Usage notes:
> * Can be used as shorthand for a CASE expression.
> * The expression and the search expressions must of the same type or
> convertible types.
> * The result expression can be a different type, but all result expressions
> must be of the same type.
> * Returns a successful match If the original expression is NULL and a search
> expression is also NULL. (Uses IS NOT DISTINCT to do the comparison.)
> * NULL can be used as a search expression.
> * Returns NULL if the final default value is omitted and none of the search
> expressions match the original expression.
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