Fix unique INCLUDE indexes on partitioned tables

We were considering the INCLUDE columns as part of the key, allowing
unicity-violating rows to be inserted in different partitions.

Concurrent development conflict in eb7ed3f3 and 8224de4f.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20190109065109.GA4285@telsasoft.com

src/backend/commands/indexcmds.c

@@ -721,7 +721,7 @@ DefineIndex(Oid relationId,
 						 errdetail("%s constraints cannot be used when partition keys include expressions.",
 								   constraint_type)));
 
-			for (j = 0; j < indexInfo->ii_NumIndexAttrs; j++)
+			for (j = 0; j < indexInfo->ii_NumIndexKeyAttrs; j++)
 			{
 				if (key->partattrs[i] == indexInfo->ii_IndexAttrNumbers[j])
 				{

src/test/regress/expected/indexing.out

@@ -1411,3 +1411,6 @@ insert into covidxpart values (4, 1);
 insert into covidxpart values (4, 1);
 ERROR:  duplicate key value violates unique constraint "covidxpart4_a_b_idx"
 DETAIL:  Key (a)=(4) already exists.
+create unique index on covidxpart (b) include (a); -- should fail
+ERROR:  insufficient columns in UNIQUE constraint definition
+DETAIL:  UNIQUE constraint on table "covidxpart" lacks column "a" which is part of the partition key.

src/test/regress/sql/indexing.sql

@@ -756,3 +756,4 @@ create unique index on covidxpart4 (a);
 alter table covidxpart attach partition covidxpart4 for values in (4);
 insert into covidxpart values (4, 1);
 insert into covidxpart values (4, 1);
+create unique index on covidxpart (b) include (a); -- should fail