Add prefix operator for TEXT type.

The prefix operator along with SP-GiST indexes can be used as an alternative
for LIKE 'word%' commands  and it doesn't have a limitation of string/prefix
length as B-Tree has.

Bump catalog version

Author: Ildus Kurbangaliev with some editorization by me
Review by: Arthur Zakirov, Alexander Korotkov, and me
Discussion: https://www.postgresql.org/message-id/flat/20180202180327.222b04b3@wp.localdomain

src/test/regress/expected/create_index.out

@@ -372,6 +372,12 @@ SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth
     48
 (1 row)
 
+SELECT count(*) FROM radix_text_tbl WHERE t ^@  'Worth';
+ count 
+-------
+     2
+(1 row)
+
 SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
                        f1                        
 -------------------------------------------------
@@ -1182,6 +1188,21 @@ SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth
     48
 (1 row)
 
+EXPLAIN (COSTS OFF)
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+                         QUERY PLAN                         
+------------------------------------------------------------
+ Aggregate
+   ->  Index Only Scan using sp_radix_ind on radix_text_tbl
+         Index Cond: (t ^@ 'Worth'::text)
+(3 rows)
+
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+ count 
+-------
+     2
+(1 row)
+
 EXPLAIN (COSTS OFF)
 SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
                      QUERY PLAN                      
@@ -1763,6 +1784,23 @@ SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth
     48
 (1 row)
 
+EXPLAIN (COSTS OFF)
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+                   QUERY PLAN                   
+------------------------------------------------
+ Aggregate
+   ->  Bitmap Heap Scan on radix_text_tbl
+         Recheck Cond: (t ^@ 'Worth'::text)
+         ->  Bitmap Index Scan on sp_radix_ind
+               Index Cond: (t ^@ 'Worth'::text)
+(5 rows)
+
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+ count 
+-------
+     2
+(1 row)
+
 RESET enable_seqscan;
 RESET enable_indexscan;
 RESET enable_bitmapscan;

src/test/regress/expected/opr_sanity.out

@@ -718,6 +718,7 @@ sha224(bytea)
 sha256(bytea)
 sha384(bytea)
 sha512(bytea)
+starts_with(text,text)
 macaddr8_eq(macaddr8,macaddr8)
 macaddr8_lt(macaddr8,macaddr8)
 macaddr8_le(macaddr8,macaddr8)
@@ -1887,7 +1888,8 @@ ORDER BY 1, 2, 3;
        4000 |           25 | <<=
        4000 |           26 | >>
        4000 |           27 | >>=
-(121 rows)
+       4000 |           28 | ^@
+(122 rows)
 
 -- Check that all opclass search operators have selectivity estimators.
 -- This is not absolutely required, but it seems a reasonable thing

src/test/regress/sql/create_index.sql

@@ -224,6 +224,8 @@ SELECT count(*) FROM radix_text_tbl WHERE t >    'Worth
 
 SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth                         St  ';
 
+SELECT count(*) FROM radix_text_tbl WHERE t ^@  'Worth';
+
 SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
 
 SELECT circle_center(f1), round(radius(f1)) as radius FROM gcircle_tbl ORDER BY f1 <-> '(200,300)'::point LIMIT 10;
@@ -441,6 +443,10 @@ EXPLAIN (COSTS OFF)
 SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth                         St  ';
 SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth                         St  ';
 
+EXPLAIN (COSTS OFF)
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+
 EXPLAIN (COSTS OFF)
 SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
 SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
@@ -578,6 +584,10 @@ EXPLAIN (COSTS OFF)
 SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth                         St  ';
 SELECT count(*) FROM radix_text_tbl WHERE t ~>~  'Worth                         St  ';
 
+EXPLAIN (COSTS OFF)
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+SELECT count(*) FROM radix_text_tbl WHERE t ^@	 'Worth';
+
 RESET enable_seqscan;
 RESET enable_indexscan;
 RESET enable_bitmapscan;