Address comments

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

@@ -249,30 +249,30 @@ Currently, using a _precision_ greater than 3 doesn't make any difference to the
 function as the maximum number of second fractional digits returned is 3 (milliseconds).
 
 [[sql-functions-datetime-add]]
-==== `DATE_ADD/DATE_ADD/TIMESTAMPADD/TIMESTAMP_ADD`
+==== `DATE_ADD/DATEADD/TIMESTAMPADD/TIMESTAMP_ADD`
 
 .Synopsis:
 [source, sql]
 --------------------------------------------------
-DATE_PART(
+DATE_ADD(
     string_exp, <1>
     integer_exp, <2>
     datetime_exp) <3>
 --------------------------------------------------
 
 *Input*:
 
-<1> string expression denoting the unit to add to the date/datetime
-<2> integer expression denoting how many times the above unit should be added/subtracted (if it's negative)
-to/from the date/datetime
+<1> string expression denoting the date/time unit to add to the date/datetime
+<2> integer expression denoting how many times the above unit should be added to/from the date/datetime,
+if a negative value is used it results to a subtraction from the date/datetime
 <3> date/datetime expression
 
 *Output*: datetime
 
 .Description:
 
-Add/Subtract the given number of units to/from a date/datetime. If any of the three arguments is `null`
-a `null` is returned.
+Add the given number of date/time units to a date/datetime. If the number of units is negative then it's subtracted from
+the date/datetime.If any of the three arguments is `null` a `null` is returned.
 
 [cols="^,^"]
 |===

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

@@ -138,10 +138,10 @@ DATE_ADD('mcs', -12345678, '2019-09-04T11:22:33.123Z'::datetime)::string as dt_m
 
 selectAddWithDate
 schema::dt_year:ts|dt_quarter:ts|dt_month:ts|dt_week:ts|dt_day:ts|dt_hours:ts|dt_min:ts|dt_sec:ts|dt_millis:s|dt_mcsec:s|dt_nsec:s
-SELECT DATE_ADD('year', 10, '2019-09-04'::date) as dt_year, DATE_ADD('quarter', -10, '2019-09-04'::date) as dt_quarter, DATE_ADD('month', 20, '2019-09-04'::date) as dt_month,
-DATE_ADD('week', -50, '2019-09-04'::date) as dt_week, DATE_ADD('day', 200, '2019-09-04'::date) as dt_day,
-DATE_ADD('hours', -3000, '2019-09-04'::date) as dt_hours, DATE_ADD('minutes', 5678, '2019-09-04'::date) as dt_min, DATE_ADD('second', 987654, '2019-09-04'::date) as dt_sec,
-DATE_ADD('milliseconds', 4314144, '2019-09-04'::date)::string as dt_millis, DATE_ADD('mcs', -12345678, '2019-09-04'::date)::string as dt_mcsec, DATE_ADD('nanosecond', 12345600, '2019-09-04'::date)::string as dt_nsec;
+SELECT DATEADD('year', 10, '2019-09-04'::date) as dt_year, DATEADD('quarter', -10, '2019-09-04'::date) as dt_quarter, DATEADD('month', 20, '2019-09-04'::date) as dt_month,
+DATEADD('week', -50, '2019-09-04'::date) as dt_week, DATEADD('day', 200, '2019-09-04'::date) as dt_day,
+DATEADD('hours', -3000, '2019-09-04'::date) as dt_hours, DATEADD('minutes', 5678, '2019-09-04'::date) as dt_min, DATEADD('second', 987654, '2019-09-04'::date) as dt_sec,
+DATEADD('milliseconds', 4314144, '2019-09-04'::date)::string as dt_millis, DATEADD('mcs', -12345678, '2019-09-04'::date)::string as dt_mcsec, DATEADD('nanosecond', 12345600, '2019-09-04'::date)::string as dt_nsec;
 
        dt_year           |      dt_quarter          |       dt_month           |        dt_week           |        dt_day            |       dt_hours           |        dt_min            |        dt_sec            |         dt_millis        |       dt_mcsec           |         dt_nsec
 -------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+--------------------------+-------------------------
@@ -150,9 +150,9 @@ DATE_ADD('milliseconds', 4314144, '2019-09-04'::date)::string as dt_millis, DATE
 
 selectDateAddWithField
 schema::emp_no:i|birth_date:ts|dt_year:ts|dt_quarter:ts|dt_month:ts|dt_week:ts|dt_day:ts|dt_min:ts|dt_sec:ts
-SELECT emp_no, birth_date, DATE_ADD('year', 10, birth_date) as dt_year, DATE_ADD('quarter', -10, birth_date) as dt_quarter,
-DATE_ADD('month', 20, birth_date) as dt_month, DATE_ADD('week', -20, birth_date) as dt_week, DATE_ADD('day', 300, birth_date) as dt_day,
-DATE_ADD('minutes', 10000, birth_date) as dt_min, DATE_ADD('second', 100000, birth_date) as dt_sec
+SELECT emp_no, birth_date, TIMESTAMP_ADD('year', 10, birth_date) as dt_year, TIMESTAMP_ADD('quarter', -10, birth_date) as dt_quarter,
+TIMESTAMP_ADD('month', 20, birth_date) as dt_month, TIMESTAMP_ADD('week', -20, birth_date) as dt_week, TIMESTAMP_ADD('day', 300, birth_date) as dt_day,
+TIMESTAMP_ADD('minutes', 10000, birth_date) as dt_min, TIMESTAMP_ADD('second', 100000, birth_date) as dt_sec
 FROM test_emp WHERE emp_no >= 10032 AND emp_no <= 10042 ORDER BY 1;
 
   emp_no  |     birth_date           |       dt_year            |     dt_quarter           |      dt_month            |       dt_week            |       dt_day             |       dt_min             |       dt_sec
@@ -171,7 +171,7 @@ FROM test_emp WHERE emp_no >= 10032 AND emp_no <= 10042 ORDER BY 1;
 ;
 
 selectAddWithComplexExpressions
-SELECT gender, birth_date, DATE_ADD('months', CASE WHEN gender = 'M' THEN 10 WHEN gender = 'F' THEN -10 ELSE 100 END,
+SELECT gender, birth_date, TIMESTAMPADD('months', CASE WHEN gender = 'M' THEN 10 WHEN gender = 'F' THEN -10 ELSE 100 END,
 birth_date + INTERVAL 10 month) AS dt FROM test_emp WHERE dt > '1954-07-01'::date ORDER BY emp_no LIMIT 10;
 
   gender:s  |   birth_date:ts          |    dt:ts

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/datetime/DateAddProcessor.java

@@ -19,8 +19,8 @@ public class DateAddProcessor extends ThreeArgsDateTimeProcessor {
 
     public static final String NAME = "dtadd";
 
-    public DateAddProcessor(Processor source1, Processor source2, Processor source3, ZoneId zoneId) {
-        super(source1, source2, source3, zoneId);
+    public DateAddProcessor(Processor unit, Processor numberOfUnits, Processor timestamp, ZoneId zoneId) {
+        super(unit, numberOfUnits, timestamp, zoneId);
     }
 
     public DateAddProcessor(StreamInput in) throws IOException {

x-pack/plugin/sql/src/test/java/org/elasticsearch/xpack/sql/expression/function/scalar/datetime/DateAddPipeTests.java

@@ -50,7 +50,7 @@ public static DateAddPipe randomDateAddPipe() {
     @Override
     public void testTransform() {
         // test transforming only the properties (source, expression),
-        // skipping the children (the two parameters of the binary function) which are tested separately
+        // skipping the children (the three parameters of the function) which are tested separately
         DateAddPipe b1 = randomInstance();
 
         Expression newExpression = randomValueOtherThan(b1.expression(), this::randomDateAddPipeExpression);