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SQL: Test and fix the NULL handling of the String functions (#68379)

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Fixed the inconsistencies regarding NULL argument handling.
NULL literal vs NULL field value as function arguments in some case
resulted in different function return values.

Functions should return with the same value no matter if the argument(s)
came from a field or from a literal.

The introduced integration test tests if function calls with same
argument values (regardless of literal/field) will return with the
same output (also checks if newly added functions are added to the
testcases).

Fixed the following functions:
* Insert: NULL start, length and replacement arguments (as fields) also
result in NULL return value instead of returning the input.
* Locate: NULL pattern results in NULL return value, NULL optional start
argument handled the same as missing start argument
* Replace: NULL pattern and replacement results in NULL instead of
returning the input
* Substring: NULL start or length results in NULL instead of returning
the input

Fixes #58907
This commit is contained in:
Andras Palinkas 2021-02-05 12:30:37 -05:00 • committed by GitHub
parent 5695a63f0c
commit a3dbdae2ef
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13 changed files with 428 additions and 46 deletions
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4
docs/reference/sql/functions/string.asciidoc
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@ -107,7 +107,7 @@ CONCAT(
*Output*: string
*Description*: Returns a character string that is the result of concatenating `string_exp1` to `string_exp2`. If one of the string is `NULL`, the other string will be returned.
*Description*: Returns a character string that is the result of concatenating `string_exp1` to `string_exp2`. `NULL` input strings are treated as empty strings.
[source, sql]
--------------------------------------------------
@ -228,7 +228,7 @@ LOCATE(
*Output*: integer
*Description*: Returns the starting position of the first occurrence of `pattern` within `source`. The search for the first occurrence of `pattern` begins with the first character position in `source` unless the optional argument, `start`, is specified. If `start` is specified, the search begins with the character position indicated by the value of `start`. The first character position in `source` is indicated by the value 1. If `pattern` is not found within `source`, the value 0 is returned.
*Description*: Returns the starting position of the first occurrence of `pattern` within `source`. The optional `start` specifies the character position to start the search with. The first character position in `source` is indicated by the value 1. Not specifying `start` or specifying it as `NULL`, any negative value, 0 or 1, starts the search at the first character position. If `pattern` is not found within `source`, the value 0 is returned.
[source, sql]
--------------------------------------------------