Hi there, I’m kind of new around here, but I have had experience with all of all the so called “big iron” databases such as Oracle, IBM DB2 and Microsoft SQL Server as well as Postgresql.
They all support the notion of “ANSI padding” for CHAR columns - which means that such columns are always space padded, and they default to having this enabled (for ANSI compliance). MySQL also supports it, but it defaults to leaving it disabled for historical reasons not unlike what we have here. In my opinion we should push toward standards compliance where possible and then document where it cannot work. If users don’t like the padding on CHAR columns then they should change to VARCHAR - I believe that was its purpose in the first place, and it does not dictate any sort of “padding". I can see why you might “ban” the use of CHAR columns where they cannot be consistently supported, but VARCHAR is a different animal and I would expect it to work consistently everywhere. Cheers, Steve C On 17 Mar 2020, at 10:01 am, Dongjoon Hyun <dongjoon.h...@gmail.com<mailto:dongjoon.h...@gmail.com>> wrote: Hi, Reynold. (And +Michael Armbrust) If you think so, do you think it's okay that we change the return value silently? Then, I'm wondering why we reverted `TRIM` functions then? > Are we sure "not padding" is "incorrect"? Bests, Dongjoon. On Sun, Mar 15, 2020 at 11:15 PM Gourav Sengupta <gourav.sengu...@gmail.com<mailto:gourav.sengu...@gmail.com>> wrote: Hi, 100% agree with Reynold. Regards, Gourav Sengupta On Mon, Mar 16, 2020 at 3:31 AM Reynold Xin <r...@databricks.com<mailto:r...@databricks.com>> wrote: Are we sure "not padding" is "incorrect"? I don't know whether ANSI SQL actually requires padding, but plenty of databases don't actually pad. https://docs.snowflake.net/manuals/sql-reference/data-types-text.html<https://aus01.safelinks.protection.outlook.com/?url=https:%2F%2Fdocs.snowflake.net%2Fmanuals%2Fsql-reference%2Fdata-types-text.html%23:~:text%3DCHAR%2520%252C%2520CHARACTER%2C(1)%2520is%2520the%2520default.%26text%3DSnowflake%2520currently%2520deviates%2520from%2520common%2Cspace-padded%2520at%2520the%2520end.&data=02%7C01%7Cscoy%40infomedia.com.au%7C5346c8d2675342008b5708d7c9fdff54%7C45d5407150f849caa59f9457123dc71c%7C0%7C0%7C637199965062044368&sdata=BvnZTTPTZBAi8oGWIvJk2fC%2FYSgdvq%2BAxtOj0nVzufk%3D&reserved=0> : "Snowflake currently deviates from common CHAR semantics in that strings shorter than the maximum length are not space-padded at the end." MySQL: https://stackoverflow.com/questions/53528645/why-char-dont-have-padding-in-mysql<https://aus01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstackoverflow.com%2Fquestions%2F53528645%2Fwhy-char-dont-have-padding-in-mysql&data=02%7C01%7Cscoy%40infomedia.com.au%7C5346c8d2675342008b5708d7c9fdff54%7C45d5407150f849caa59f9457123dc71c%7C0%7C0%7C637199965062044368&sdata=3OGLht%2Fa28GcKhAGwJPXIR%2BMODiIwXGVuNuResZqwXM%3D&reserved=0> On Sun, Mar 15, 2020 at 7:02 PM, Dongjoon Hyun <dongjoon.h...@gmail.com<mailto:dongjoon.h...@gmail.com>> wrote: Hi, Reynold. Please see the following for the context. https://issues.apache.org/jira/browse/SPARK-31136<https://aus01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fissues.apache.org%2Fjira%2Fbrowse%2FSPARK-31136&data=02%7C01%7Cscoy%40infomedia.com.au%7C5346c8d2675342008b5708d7c9fdff54%7C45d5407150f849caa59f9457123dc71c%7C0%7C0%7C637199965062054364&sdata=pWQ9QhfVY4Uzyc8oIJ1QONQ0zOBAQ2DGSemyBj%2BvFeM%3D&reserved=0> "Revert SPARK-30098 Use default datasource as provider for CREATE TABLE syntax" I raised the above issue according to the new rubric, and the banning was the proposed alternative to reduce the potential issue. Please give us your opinion since it's still PR. Bests, Dongjoon. On Sat, Mar 14, 2020 at 17:54 Reynold Xin <r...@databricks.com<mailto:r...@databricks.com>> wrote: I don’t understand this change. Wouldn’t this “ban” confuse the hell out of both new and old users? For old users, their old code that was working for char(3) would now stop working. For new users, depending on whether the underlying metastore char(3) is either supported but different from ansi Sql (which is not that big of a deal if we explain it) or not supported. On Sat, Mar 14, 2020 at 3:51 PM Dongjoon Hyun <dongjoon.h...@gmail.com<mailto:dongjoon.h...@gmail.com>> wrote: Hi, All. Apache Spark has been suffered from a known consistency issue on `CHAR` type behavior among its usages and configurations. However, the evolution direction has been gradually moving forward to be consistent inside Apache Spark because we don't have `CHAR` offically. The following is the summary. With 1.6.x ~ 2.3.x, `STORED PARQUET` has the following different result. (`spark.sql.hive.convertMetastoreParquet=false` provides a fallback to Hive behavior.) spark-sql> CREATE TABLE t1(a CHAR(3)); spark-sql> CREATE TABLE t2(a CHAR(3)) STORED AS ORC; spark-sql> CREATE TABLE t3(a CHAR(3)) STORED AS PARQUET; spark-sql> INSERT INTO TABLE t1 SELECT 'a '; spark-sql> INSERT INTO TABLE t2 SELECT 'a '; spark-sql> INSERT INTO TABLE t3 SELECT 'a '; spark-sql> SELECT a, length(a) FROM t1; a 3 spark-sql> SELECT a, length(a) FROM t2; a 3 spark-sql> SELECT a, length(a) FROM t3; a 2 Since 2.4.0, `STORED AS ORC` became consistent. (`spark.sql.hive.convertMetastoreOrc=false` provides a fallback to Hive behavior.) spark-sql> SELECT a, length(a) FROM t1; a 3 spark-sql> SELECT a, length(a) FROM t2; a 2 spark-sql> SELECT a, length(a) FROM t3; a 2 Since 3.0.0-preview2, `CREATE TABLE` (without `STORED AS` clause) became consistent. (`spark.sql.legacy.createHiveTableByDefault.enabled=true` provides a fallback to Hive behavior.) spark-sql> SELECT a, length(a) FROM t1; a 2 spark-sql> SELECT a, length(a) FROM t2; a 2 spark-sql> SELECT a, length(a) FROM t3; a 2 In addition, in 3.0.0, SPARK-31147 aims to ban `CHAR/VARCHAR` type in the following syntax to be safe. CREATE TABLE t(a CHAR(3)); https://github.com/apache/spark/pull/27902<https://aus01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fapache%2Fspark%2Fpull%2F27902&data=02%7C01%7Cscoy%40infomedia.com.au%7C5346c8d2675342008b5708d7c9fdff54%7C45d5407150f849caa59f9457123dc71c%7C0%7C0%7C637199965062054364&sdata=lhwUP5TcTtaO%2BLUTmx%2BPTjT0ASXPrQ7oKLL0N6EG0Ug%3D&reserved=0> This email is sent out to inform you based on the new policy we voted. The recommendation is always using Apache Spark's native type `String`. Bests, Dongjoon. References: 1. "CHAR implementation?", 2017/09/15 https://lists.apache.org/thread.html/96b004331d9762e356053b5c8c97e953e398e489d15e1b49e775702f%40%3Cdev.spark.apache.org%3E<https://aus01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.apache.org%2Fthread.html%2F96b004331d9762e356053b5c8c97e953e398e489d15e1b49e775702f%2540%253Cdev.spark.apache.org%253E&data=02%7C01%7Cscoy%40infomedia.com.au%7C5346c8d2675342008b5708d7c9fdff54%7C45d5407150f849caa59f9457123dc71c%7C0%7C0%7C637199965062064358&sdata=6hkno6zKTkcIrO%2FJo4hTYihsYvNynMuWcxhzL0fZR68%3D&reserved=0> 2. "FYI: SPARK-30098 Use default datasource as provider for CREATE TABLE syntax", 2019/12/06 https://lists.apache.org/thread.html/493f88c10169680191791f9f6962fd16cd0ffa3b06726e92ed04cbe1%40%3Cdev.spark.apache.org%3E<https://aus01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.apache.org%2Fthread.html%2F493f88c10169680191791f9f6962fd16cd0ffa3b06726e92ed04cbe1%2540%253Cdev.spark.apache.org%253E&data=02%7C01%7Cscoy%40infomedia.com.au%7C5346c8d2675342008b5708d7c9fdff54%7C45d5407150f849caa59f9457123dc71c%7C0%7C0%7C637199965062064358&sdata=QJnEU3mvUJff53Gw8F%2FAbxzd%2F8ZA1hhuoQwicX4ZXyI%3D&reserved=0> This email contains confidential information of and is the copyright of Infomedia. It must not be forwarded, amended or disclosed without consent of the sender. If you received this message by mistake, please advise the sender and delete all copies. 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