Support FETCH FIRST WITH TIES WITH TIES is an option to the FETCH FIRST N ROWS clause (the SQL standard's spelling of LIMIT), where you additionally get rows that compare equal to the last of those N rows by the columns in the mandatory ORDER BY clause. There was a proposal by Andrew Gierth to implement this functionality in a more powerful way that would yield more features, but the other patch had not been finished at this time, so we decided to use this one for now in the spirit of incremental development. Author: Surafel Temesgen <email@example.com> Reviewed-by: Álvaro Herrera <firstname.lastname@example.org> Reviewed-by: Tomas Vondra <email@example.com> Discussion: https://postgr.es/m/CALAY4q9ky7rD_A4vf=FVQvCGngm3LOes-ky0J6euMrg=_Sefirstname.lastname@example.org Discussion: https://email@example.com
On 23rd of December, Tom Lane committed patch:
Support ordered-set (WITHIN GROUP) aggregates. This patch introduces generic support for ordered-set and hypothetical-set aggregate functions, as well as implementations of the instances defined in SQL:2008 (percentile_cont(), percentile_disc(), rank(), dense_rank(), percent_rank(), cume_dist()). We also added mode() though it is not in the spec, as well as versions of percentile_cont() and percentile_disc() that can compute multiple percentile values in one pass over the data. Unlike the original submission, this patch puts full control of the sorting process in the hands of the aggregate's support functions. To allow the support functions to find out how they're supposed to sort, a new API function AggGetAggref() is added to nodeAgg.c. This allows retrieval of the aggregate call's Aggref node, which may have other uses beyond the immediate need. There is also support for ordered-set aggregates to install cleanup callback functions, so that they can be sure that infrastructure such as tuplesort objects gets cleaned up. In passing, make some fixes in the recently-added support for variadic aggregates, and make some editorial adjustments in the recent FILTER additions for aggregates. Also, simplify use of IsBinaryCoercible() by allowing it to succeed whenever the target type is ANY or ANYELEMENT. It was inconsistent that it dealt with other polymorphic target types but not these. Atri Sharma and Andrew Gierth; reviewed by Pavel Stehule and Vik Fearing, and rather heavily editorialized upon by Tom Lane
Every so often someone asks why sorting behaves irrational. Like here:
$ select string from test order by string; string ---------- dean deer de luca depesz de vil dyslexia (6 rows)
Why aren't “de luca" and “de vil" together?
On 8th of February, Peter Eisentraut committed patch:
Per-column collation support This adds collation support for columns and domains, a COLLATE clause to override it per expression, and B-tree index support. Peter Eisentraut reviewed by Pavel Stehule, Itagaki Takahiro, Robert Haas, Noah Misch Branch ------ master
Let's imagine simple situation – you have table of objects (each with id), and you want objects 3, 71, 5 and 16. And in that order!
How to do it?
On 15th of December Tom Lane committed patch by Andrew Gierth (aka RhodiumToad), which adds interesting capability:
Log Message: ----------- Support ORDER BY within aggregate function calls, at long last providing a non-kluge method for controlling the order in which values are fed to an aggregate function. At the same time eliminate the old implementation restriction that DISTINCT was only supported for single-argument aggregates. Possibly release-notable behavioral change: formerly, agg(DISTINCT x) dropped null values of x unconditionally. Now, it does so only if the agg transition function is strict; otherwise nulls are treated as DISTINCT normally would, ie, you get one copy. Andrew Gierth, reviewed by Hitoshi Harada