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  1. IMPALA
  2. IMPALA-7739

Errata in documentation of decode() method

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Details

    • Improvement
    • Status: Closed
    • Minor
    • Resolution: Fixed
    • Impala 3.0
    • Impala 3.1.0
    • Docs
    • None
    • ghx-label-5

    Description

      Consider the description of decode() in the docs. Original text:

      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.

      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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              arodoni Alexandra Rodoni
              Paul.Rogers Paul Rogers
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                Updated:
                Resolved: