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Gabor Kaszab commented on IMPALA-4018: -------------------------------------- Understood. Thanks for the explanation, Greg! So as far as I understand the plan is to introduce CAST(..FORMAT..) with SQL format from the beginning and leave e.g. to_timestamp() and from_timestamp() to use Java format with an additional flag to switch them to SQL pattern. If this is the case then I'm worried a bit to introduce inconsistency within Impala. I can imagine using one pattern here but another there by default would cause some confusion for the users. [~grahn] Do you think we could avoid this somehow? Can we deprecate the functions using Java syntax eventually and indicate to the users at this point that they should migrate off? (On a sidenote, I found no documentation about the current date time formats in our docs so it's a great moment to add them alongside with the new format. [~arodoni_cloudera] This is just an FYI.) Another concern was raised by [~Paul.Rogers] on the code review: As view definitions can be written to HMS should we be worried that Hive won't be able to read them if they are written with SQL pattern? In addition Hive doesn't have FORMAT clause for CAST so it brings in another inconsistency between the systems. Should we initiate a conversation with the Hive community to handle the same on their side? > Add support for SQL:2016 datetime templates/patterns/masks to CAST(... AS ... > FORMAT <template>) > ------------------------------------------------------------------------------------------------ > > Key: IMPALA-4018 > URL: https://issues.apache.org/jira/browse/IMPALA-4018 > Project: IMPALA > Issue Type: New Feature > Components: Frontend > Affects Versions: Impala 2.2.4 > Reporter: Greg Rahn > Assignee: Gabor Kaszab > Priority: Critical > Labels: ansi-sql, compatibility, sql-language > > *Summary* > The format masks/templates for currently are implemented using the [Java > SimpleDateFormat > patterns|http://docs.oracle.com/javase/8/docs/api/java/text/SimpleDateFormat.html], > and although this is what Hive has implemented, it is not what most standard > SQL systems implement. For example see > [Vertica|https://my.vertica.com/docs/7.2.x/HTML/Content/Authoring/SQLReferenceManual/Functions/Formatting/TemplatePatternsForDateTimeFormatting.htm], > > [Netezza|http://www.ibm.com/support/knowledgecenter/SSULQD_7.2.1/com.ibm.nz.dbu.doc/r_dbuser_ntz_sql_extns_templ_patterns_date_time_conv.html], > > [Oracle|https://docs.oracle.com/database/121/SQLRF/sql_elements004.htm#SQLRF00212], > and > [PostgreSQL|https://www.postgresql.org/docs/9.5/static/functions-formatting.html#FUNCTIONS-FORMATTING-DATETIME-TABLE]. > > *Examples of incompatibilities* > {noformat} > -- PostgreSQL/Netezza/Vertica/Oracle > select to_timestamp('May 15, 2015 12:00:00', 'mon dd, yyyy hh:mi:ss'); > -- Impala > select to_timestamp('May 15, 2015 12:00:00', 'MMM dd, yyyy HH:mm:ss'); > -- PostgreSQL/Netezza/Vertica/Oracle > select to_timestamp('2015-02-14 20:19:07','yyyy-mm-dd hh24:mi:ss'); > -- Impala > select to_timestamp('2015-02-14 20:19:07','yyyy-MM-dd HH:mm:ss'); > -- Vertica/Oracle > select to_timestamp('2015-02-14 20:19:07.123456','yyyy-mm-dd hh24:mi:ss.ff'); > -- Impala > select to_timestamp('2015-02-14 20:19:07.123456','yyyy-MM-dd > HH:mm:ss.SSSSSS'); > {noformat} > *Considerations* > Because this is a change in default behavior for to_timestamp(), if possible, > having a feature flag to revert to the legacy Java SimpleDateFormat patterns > should be strongly considered. This would allow users to chose the behavior > they desire and scope it to a session if need be. > SQL:2016 defines the following datetime templates > {noformat} > <datetime template> ::= > { <datetime template part> }... > <datetime template part> ::= > <datetime template field> > | <datetime template delimiter> > <datetime template field> ::= > <datetime template year> > | <datetime template rounded year> > | <datetime template month> > | <datetime template day of month> > | <datetime template day of year> > | <datetime template 12-hour> > | <datetime template 24-hour> > | <datetime template minute> > | <datetime template second of minute> > | <datetime template second of day> > | <datetime template fraction> > | <datetime template am/pm> > | <datetime template time zone hour> > | <datetime template time zone minute> > <datetime template delimiter> ::= > <minus sign> > | <period> > | <solidus> > | <comma> > | <apostrophe> > | <semicolon> > | <colon> > | <space> > <datetime template year> ::= > YYYY | YYY | YY | Y > <datetime template rounded year> ::= > RRRR | RR > <datetime template month> ::= > MM > <datetime template day of month> ::= > DD > <datetime template day of year> ::= > DDD > <datetime template 12-hour> ::= > HH | HH12 > <datetime template 24-hour> ::= > HH24 > <datetime template minute> ::= > MI > <datetime template second of minute> ::= > SS > <datetime template second of day> ::= > SSSSS > <datetime template fraction> ::= > FF1 | FF2 | FF3 | FF4 | FF5 | FF6 | FF7 | FF8 | FF9 > <datetime template am/pm> ::= > A.M. | P.M. > <datetime template time zone hour> ::= > TZH > <datetime template time zone minute> ::= > TZM > {noformat} > SQL:2016 also introduced the FORMAT clause for CAST which is the standard way > to do string <> datetime conversions > {noformat} > <cast specification> ::= > CAST <left paren> > <cast operand> AS <cast target> > [ FORMAT <cast template> ] > <right paren> > <cast operand> ::= > <value expression> > | <implicitly typed value specification> > <cast target> ::= > <domain name> > | <data type> > <cast template> ::= > <character string literal> > {noformat} > For example: > {noformat} > CAST(<datetime> AS <char string type> [FORMAT <template>]) > CAST(<char string> AS <datetime type> [FORMAT <template>]) > cast(dt as string format 'DD-MM-YYYY') > cast('01-05-2017' as date format 'DD-MM-YYYY') > {noformat} -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-all-unsubscr...@impala.apache.org For additional commands, e-mail: issues-all-h...@impala.apache.org