Address comments

Author: matriv

docs/reference/sql/functions/date-time.asciidoc

@@ -94,7 +94,7 @@ include-tagged::{sql-specs}/docs.csv-spec[dtIntervalMul]
 beta[]
 
 [[sql-functions-current-date]]
-==== `CURRENT_TIMESTAMP/CURDATE`
+==== `CURRENT_DATE/CURDATE`
 
 .Synopsis:
 [source, sql]
@@ -115,7 +115,7 @@ It can be used both as a keyword: `CURRENT_DATE` or as a function with no argume
 [NOTE]
 Unlike CURRENT_DATE, `CURDATE()` can only be used as a function with no arguments and not as a keyword.
 
-This method always returns the same value within a query.
+This method always returns the same value for its every occurrence within the same query.
 
 ["source","sql",subs="attributes,callouts,macros"]
 --------------------------------------------------
@@ -157,7 +157,7 @@ Returns the date/time when the current query reached the server.
 As a function, `CURRENT_TIMESTAMP()` accepts _precision_ as an optional
 parameter for rounding the second fractional digits (nanoseconds).
 
-This method always returns the same value within a query.
+This method always returns the same value for its every occurrence within the same query.
 
 ["source","sql",subs="attributes,callouts,macros"]
 --------------------------------------------------
@@ -464,7 +464,8 @@ NOW()
 .Description:
 
 This function offers the same functionality as <<sql-functions-current-timestamp,CURRENT_TIMESTAMP()>> function: returns
-the datetime when the current query reached the server. This method always returns the same value within a query.
+the datetime when the current query reached the server. This method always returns the same value for its every
+occurrence within the same query.
 
 ["source","sql",subs="attributes,callouts,macros"]
 --------------------------------------------------
@@ -543,7 +544,8 @@ TODAY()
 .Description:
 
 This function offers the same functionality as <<sql-functions-current-date,CURRENT_DATE()>> function: returns
-the date when the current query reached the server. This method always returns the same value within a query.
+the date when the current query reached the server. This method always returns the same value for its every occurrence
+within the same query.
 
 ["source","sql",subs="attributes,callouts,macros"]
 --------------------------------------------------

x-pack/plugin/sql/qa/src/main/resources/date.csv-spec

@@ -27,11 +27,11 @@ SELECT YEAR(TODAY()) / 1000 AS result;
 ;
 
 todayIntervalSubstraction
-SELECT YEAR(TODAY() - INTERVAL 2 YEARS) / 1000 AS result;
+SELECT TRUNCATE(YEAR(TODAY() - INTERVAL 50 YEARS) / 1000) AS result;
 
     result
 ---------------
-2
+1
 ;
 
 
@@ -53,20 +53,20 @@ Tuval
 ;
 
 currentDateFilterScript
-SELECT first_name FROM test_emp WHERE YEAR(hire_date) - YEAR(TODAY()) / 1000 > 10 ORDER BY first_name ASC LIMIT 10;
-
-  first_name
----------------
-Alejandro
-Amabile
-Anneke
-Anoosh
-Arumugam
-Basil
-Berhard
-Berni
-Bezalel
-Bojan
+SELECT first_name, TRUNCATE(YEAR(hire_date) - YEAR(TODAY()) / 1000) AS filter FROM test_emp
+WHERE TRUNCATE(YEAR(hire_date) - YEAR(TODAY()) / 1000) > 1990 ORDER BY first_name ASC LIMIT 10;
+
+  first_name   |  filter
+Cristinel      |1991
+Kazuhito       |1993
+Kenroku        |1992
+Lillian        |1997
+Magy           |1991
+Mayumi         |1993
+Mingsen        |1992
+Sailaja        |1994
+Saniya         |1992
+Shahaf         |1993
 ;
 
 dateExtractDateParts
@@ -142,3 +142,23 @@ SELECT YEAR(CAST('2019-01-21' AS DATE) + INTERVAL '1-2' YEAR TO MONTH) AS y, MON
 y:i       | m:i
 2020      | 3
 ;
+
+orderByCurrentDate
+SELECT first_name FROM test_emp ORDER BY TODAY(), first_name LIMIT 5;
+
+  first_name
+---------------
+Alejandro
+Amabile
+Anneke
+Anoosh
+Arumugam
+;
+
+groupByCurrentDate
+SELECT MAX(salary) FROM test_emp GROUP BY TODAY();
+
+  MAX(salary)
+---------------
+74999
+;

x-pack/plugin/sql/qa/src/main/resources/datetime.sql-spec

@@ -120,6 +120,12 @@ SELECT DAY_OF_WEEK(birth_date) day, COUNT(*) c FROM test_emp WHERE DAY_OF_WEEK(b
 currentTimestampYear
 SELECT YEAR(CURRENT_TIMESTAMP()) AS result;
 
+orderByCurrentTimestamp
+SELECT first_name FROM test_emp ORDER BY NOW(), first_name LIMIT 5;
+
+groupByCurrentTimestamp
+SELECT MAX(salary) FROM test_emp GROUP BY NOW();
+
 //
 // H2 uses the local timezone instead of the specified one
 //
@@ -131,3 +137,4 @@ SELECT HOUR(CURRENT_TIMESTAMP()) AS result;
 
 currentTimestampMinute-Ignore
 SELECT MINUTE(CURRENT_TIMESTAMP()) AS result;
+

x-pack/plugin/sql/src/main/antlr/SqlBase.g4

@@ -215,7 +215,6 @@ valueExpression
 primaryExpression
     : castExpression                                                                 #cast
     | extractExpression                                                              #extract
-    | builtinDateFunction                                                            #currentDateFunction
     | builtinDateTimeFunction                                                        #currentDateTimeFunction
     | constant                                                                       #constantDefault
     | (qualifiedName DOT)? ASTERISK                                                  #star
@@ -236,12 +235,9 @@ castTemplate
     : CAST '(' expression AS dataType ')'
     ;
 
-builtinDateFunction
-    : name=CURRENT_DATE ('(' ')')?
-    ;
-
 builtinDateTimeFunction
-    : name=CURRENT_TIMESTAMP ('(' precision=INTEGER_VALUE? ')')?
+    : name=CURRENT_DATE ('(' ')')?
+    | name=CURRENT_TIMESTAMP ('(' precision=INTEGER_VALUE? ')')?
     ;
 
 convertTemplate