James, Just a note that the list doesn't support attachments. I'd suggest creating a Google Doc with the contents.
-- Michael Mior mm...@uwaterloo.ca Le mer. 30 mai 2018 à 04:23, James Duong <jdu...@dremio.com> a écrit : > I've recorded my thoughts on this in the attached document > > A few notes: > - TimestampAdd has very well-spec'd behavior as part of ODBC. For example > the semantics for how to handle adding a second to a date value are clearly > defined. I experimented with a few different databases for how this is > handled with datetime_plus and didn't find it consistent. > - Transforming a TimestampAdd expression to datetime_plus would require > multiplying a 'unit' interval by the expression used for the interval > parameter in TimestampAdd. This looks odd in generated SQL, and if you were > go to back to timestampadd, the original intent wouldn't be clear. > - There are a few units in timestampadd that are not directly supported by > intervals (week, quarter, millennium, etc) > > So I wouldn't recommend datetime_plus. I'd recommend a new structure > similar to timestampadd, but with features to transform to datetime_plus. > > On Mon, May 28, 2018 at 6:52 PM, Julian Hyde <jh...@apache.org> wrote: > >> I think we should use the datetime_plus operator. It is standard, and >> sufficiently general. Its second argument needs to be an interval >> value, not necessarily an interval literal. >> >> On Mon, May 28, 2018 at 2:35 PM, James Duong <jdu...@dremio.com> wrote: >> > There are essentially two ways to add an interval to a datetime vaue in >> > Calcite >> > >> > Call the timestampadd() function: >> > select {fn timestampadd(year, 1, hire_date)}... >> > >> > Use datetime_plus interval arithmetic: >> > select hire_date + interval '1' year >> > >> > >> > Note that timestampadd's second argument does not need to be a literal. >> > Often it is a column expression. For datetime_plus literals are usually >> > used. >> > >> > I propose we create a new SqlOperator that can canonicalize both of >> these >> > inputs into one node. This lets us apply any transformations on this >> > canonical type regardless of what the original query was. >> > >> > It takes in the following arguments: >> > 1. A date/time/timestamp input >> > 2. an interval input as an integer >> > 3. a time unit for the input >> > 4. a synthetic argument indicating the source form of the function call >> > (either datetime_plus or timestampadd). >> > >> > >> > The idea is that this canonical form is easy to get into for both types, >> > and provides methods to easily convert to either type. This would help >> with >> > unparsing in SqlDialects (you do not need to implement pushdown for both >> > types of inputs). >> > >