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simplylizz committed Jul 31, 2019
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- Since Spark 3.0, if files or subdirectories disappear during recursive directory listing (i.e. they appear in an intermediate listing but then cannot be read or listed during later phases of the recursive directory listing, due to either concurrent file deletions or object store consistency issues) then the listing will fail with an exception unless `spark.sql.files.ignoreMissingFiles` is `true` (default `false`). In previous versions, these missing files or subdirectories would be ignored. Note that this change of behavior only applies during initial table file listing (or during `REFRESH TABLE`), not during query execution: the net change is that `spark.sql.files.ignoreMissingFiles` is now obeyed during table file listing / query planning, not only at query execution time.

- Since Spark 3.0, missing validation of `LongType` value in pyspark's `createDataframe` added. Previously `LongType` was not verified and resulted in `None` in case of wrong value. To have `None` instead of any validation error set `verifySchema=False`.

- Since Spark 3.0, substitution order of nested WITH clauses is changed and an inner CTE definition takes precedence over an outer. In version 2.4 and earlier, `WITH t AS (SELECT 1), t2 AS (WITH t AS (SELECT 2) SELECT * FROM t) SELECT * FROM t2` returns `1` while in version 3.0 it returns `2`. The previous behaviour can be restored by setting `spark.sql.legacy.ctePrecedence.enabled` to `true`.

- Since Spark 3.0, the `add_months` function does not adjust the resulting date to a last day of month if the original date is a last day of months. For example, `select add_months(DATE'2019-02-28', 1)` results `2019-03-28`. In Spark version 2.4 and earlier, the resulting date is adjusted when the original date is a last day of months. For example, adding a month to `2019-02-28` results in `2019-03-31`.
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