SQL: Wrong Null folding of functions and operators. #35872
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matriv
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Logical operators `OR` and `AND` as well as conditional functions (`COALESCE`, `LEAST`, `GREATEST`, etc.) cannot be folded to NULL if one of their children is NULL as is the case for most of the functions. Therefore, their `nullable()` implementation cannot return `true`. On the other hand they cannot return `false` as if they're wrapped within an `IS NULL` or `IS NOT NULL` expression, the expression will be folded to `false` and `true` respectively leading to wrong results. Change the signature of `nullable()` method and add a third value `UKNOWN` to handle these cases. Fixes: elastic#35872
matriv
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Logical operators OR and AND as well as conditional functions (COALESCE, LEAST, GREATEST, etc.) cannot be folded to NULL if one of their children is NULL as is the case for most of the functions. Therefore, their nullable() implementation cannot return true. On the other hand they cannot return false as if they're wrapped within an IS NULL or IS NOT NULL expression, the expression will be folded to false and true respectively leading to wrong results. Change the signature of nullable() method and add a third value UKNOWN to handle these cases. Fixes: #35872
matriv
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that referenced
this issue
Jan 6, 2019
Logical operators OR and AND as well as conditional functions (COALESCE, LEAST, GREATEST, etc.) cannot be folded to NULL if one of their children is NULL as is the case for most of the functions. Therefore, their nullable() implementation cannot return true. On the other hand they cannot return false as if they're wrapped within an IS NULL or IS NOT NULL expression, the expression will be folded to false and true respectively leading to wrong results. Change the signature of nullable() method and add a third value UKNOWN to handle these cases. Fixes: #35872
matriv
added a commit
that referenced
this issue
Jan 6, 2019
Logical operators OR and AND as well as conditional functions (COALESCE, LEAST, GREATEST, etc.) cannot be folded to NULL if one of their children is NULL as is the case for most of the functions. Therefore, their nullable() implementation cannot return true. On the other hand they cannot return false as if they're wrapped within an IS NULL or IS NOT NULL expression, the expression will be folded to false and true respectively leading to wrong results. Change the signature of nullable() method and add a third value UKNOWN to handle these cases. Fixes: #35872
matriv
added a commit
that referenced
this issue
Jan 6, 2019
Logical operators OR and AND as well as conditional functions (COALESCE, LEAST, GREATEST, etc.) cannot be folded to NULL if one of their children is NULL as is the case for most of the functions. Therefore, their nullable() implementation cannot return true. On the other hand they cannot return false as if they're wrapped within an IS NULL or IS NOT NULL expression, the expression will be folded to false and true respectively leading to wrong results. Change the signature of nullable() method and add a third value UKNOWN to handle these cases. Fixes: #35872
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COALESCEbut also other functions and operators (e.g.:AND,OR) returnfalsein theirnullable()implementation. Therefore if they are nested insideIS NULLorIS NOT NULL, theFoldNull()rule will wrongly fold them tofalseandtruerespectively.Here is an example of a query that because of the folding returns wrong results:
returns empty list:
but it should return:
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