[SPARK-19951][SQL] Add string concatenate operator || to Spark SQL

sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4

@@ -541,7 +541,7 @@ valueExpression
     : primaryExpression                                                                      #valueExpressionDefault
     | operator=(MINUS | PLUS | TILDE) valueExpression                                        #arithmeticUnary
     | left=valueExpression operator=(ASTERISK | SLASH | PERCENT | DIV) right=valueExpression #arithmeticBinary
-    | left=valueExpression operator=(PLUS | MINUS) right=valueExpression                     #arithmeticBinary
+    | left=valueExpression operator=(PLUS | MINUS | CONCAT_PIPE) right=valueExpression       #arithmeticBinary
     | left=valueExpression operator=AMPERSAND right=valueExpression                          #arithmeticBinary
     | left=valueExpression operator=HAT right=valueExpression                                #arithmeticBinary
     | left=valueExpression operator=PIPE right=valueExpression                               #arithmeticBinary
@@ -582,7 +582,7 @@ comparisonOperator
     ;
 
 arithmeticOperator
-    : PLUS | MINUS | ASTERISK | SLASH | PERCENT | DIV | TILDE | AMPERSAND | PIPE | HAT
+    : PLUS | MINUS | ASTERISK | SLASH | PERCENT | DIV | TILDE | AMPERSAND | PIPE | CONCAT_PIPE | HAT
     ;
 
 predicateOperator
@@ -861,6 +861,7 @@ DIV: 'DIV';
 TILDE: '~';
 AMPERSAND: '&';
 PIPE: '|';
+CONCAT_PIPE: '||';
 HAT: '^';
 
 PERCENTLIT: 'PERCENT';

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala

@@ -998,6 +998,8 @@ class AstBuilder extends SqlBaseBaseVisitor[AnyRef] with Logging {
         Add(left, right)
       case SqlBaseParser.MINUS =>
         Subtract(left, right)
+      case SqlBaseParser.CONCAT_PIPE =>
+        Concat(left :: right :: Nil)
       case SqlBaseParser.AMPERSAND =>
         BitwiseAnd(left, right)
       case SqlBaseParser.HAT =>

sql/core/src/test/resources/sql-tests/inputs/arithmetic.sql → sql/core/src/test/resources/sql-tests/inputs/operator.sql

@@ -32,3 +32,11 @@ select 1 - 2;
 select 2 * 5;
 select 5 % 3;
 select pmod(-7, 3);
+
+-- check operator precedence
+explain select 'a' || 1 + 2;
+explain select 1 - 2 || 'b';
+explain select 2 * 4  + 3 || 'b';
+explain select 3 + 1 || 'a' || 4 / 2;
+explain select 1 == 1 OR 'a' || 'b' ==  'ab';
+explain select 'a' || 'c' == 'ac' AND 2 == 3;

sql/core/src/test/resources/sql-tests/inputs/string-functions.sql

@@ -1,3 +1,6 @@
 -- Argument number exception
 select concat_ws();
 select format_string();
+
+-- A pipe operator for string concatenation
+select 'a' || 'b' || 'c';

sql/core/src/test/resources/sql-tests/results/operator.sql.out

@@ -0,0 +1,286 @@
+-- Automatically generated by SQLQueryTestSuite
+-- Number of queries: 34
+
+
+-- !query 0
+select -100
+-- !query 0 schema
+struct<-100:int>
+-- !query 0 output
+-100
+
+
+-- !query 1
+select +230
+-- !query 1 schema
+struct<230:int>
+-- !query 1 output
+230
+
+
+-- !query 2
+select -5.2
+-- !query 2 schema
+struct<-5.2:decimal(2,1)>
+-- !query 2 output
+-5.2
+
+
+-- !query 3
+select +6.8e0
+-- !query 3 schema
+struct<6.8:decimal(2,1)>
+-- !query 3 output
+6.8
+
+
+-- !query 4
+select -key, +key from testdata where key = 2
+-- !query 4 schema
+struct<(- key):int,key:int>
+-- !query 4 output
+-2	2
+
+
+-- !query 5
+select -(key + 1), - key + 1, +(key + 5) from testdata where key = 1
+-- !query 5 schema
+struct<(- (key + 1)):int,((- key) + 1):int,(key + 5):int>
+-- !query 5 output
+-2	0	6
+
+
+-- !query 6
+select -max(key), +max(key) from testdata
+-- !query 6 schema
+struct<(- max(key)):int,max(key):int>
+-- !query 6 output
+-100	100
+
+
+-- !query 7
+select - (-10)
+-- !query 7 schema
+struct<(- -10):int>
+-- !query 7 output
+10
+
+
+-- !query 8
+select + (-key) from testdata where key = 32
+-- !query 8 schema
+struct<(- key):int>
+-- !query 8 output
+-32
+
+
+-- !query 9
+select - (+max(key)) from testdata
+-- !query 9 schema
+struct<(- max(key)):int>
+-- !query 9 output
+-100
+
+
+-- !query 10
+select - - 3
+-- !query 10 schema
+struct<(- -3):int>
+-- !query 10 output
+3
+
+
+-- !query 11
+select - + 20
+-- !query 11 schema
+struct<(- 20):int>
+-- !query 11 output
+-20
+
+
+-- !query 12
+select + + 100
+-- !query 12 schema
+struct<100:int>
+-- !query 12 output
+100
+
+
+-- !query 13
+select - - max(key) from testdata
+-- !query 13 schema
+struct<(- (- max(key))):int>
+-- !query 13 output
+100
+
+
+-- !query 14
+select + - key from testdata where key = 33
+-- !query 14 schema
+struct<(- key):int>
+-- !query 14 output
+-33
+
+
+-- !query 15
+select 5 / 2
+-- !query 15 schema
+struct<(CAST(5 AS DOUBLE) / CAST(2 AS DOUBLE)):double>
+-- !query 15 output
+2.5
+
+
+-- !query 16
+select 5 / 0
+-- !query 16 schema
+struct<(CAST(5 AS DOUBLE) / CAST(0 AS DOUBLE)):double>
+-- !query 16 output
+NULL
+
+
+-- !query 17
+select 5 / null
+-- !query 17 schema
+struct<(CAST(5 AS DOUBLE) / CAST(NULL AS DOUBLE)):double>
+-- !query 17 output
+NULL
+
+
+-- !query 18
+select null / 5
+-- !query 18 schema
+struct<(CAST(NULL AS DOUBLE) / CAST(5 AS DOUBLE)):double>
+-- !query 18 output
+NULL
+
+
+-- !query 19
+select 5 div 2
+-- !query 19 schema
+struct<CAST((CAST(5 AS DOUBLE) / CAST(2 AS DOUBLE)) AS BIGINT):bigint>
+-- !query 19 output
+2
+
+
+-- !query 20
+select 5 div 0
+-- !query 20 schema
+struct<CAST((CAST(5 AS DOUBLE) / CAST(0 AS DOUBLE)) AS BIGINT):bigint>
+-- !query 20 output
+NULL
+
+
+-- !query 21
+select 5 div null
+-- !query 21 schema
+struct<CAST((CAST(5 AS DOUBLE) / CAST(NULL AS DOUBLE)) AS BIGINT):bigint>
+-- !query 21 output
+NULL
+
+
+-- !query 22
+select null div 5
+-- !query 22 schema
+struct<CAST((CAST(NULL AS DOUBLE) / CAST(5 AS DOUBLE)) AS BIGINT):bigint>
+-- !query 22 output
+NULL
+
+
+-- !query 23
+select 1 + 2
+-- !query 23 schema
+struct<(1 + 2):int>
+-- !query 23 output
+3
+
+
+-- !query 24
+select 1 - 2
+-- !query 24 schema
+struct<(1 - 2):int>
+-- !query 24 output
+-1
+
+
+-- !query 25
+select 2 * 5
+-- !query 25 schema
+struct<(2 * 5):int>
+-- !query 25 output
+10
+
+
+-- !query 26
+select 5 % 3
+-- !query 26 schema
+struct<(5 % 3):int>
+-- !query 26 output
+2
+
+
+-- !query 27
+select pmod(-7, 3)
+-- !query 27 schema
+struct<pmod(-7, 3):int>
+-- !query 27 output
+2
+
+
+-- !query 28
+explain select 'a' || 1 + 2
+-- !query 28 schema
+struct<plan:string>
+-- !query 28 output
+== Physical Plan ==
+*Project [null AS (CAST(concat(a, CAST(1 AS STRING)) AS DOUBLE) + CAST(2 AS DOUBLE))#x]
++- Scan OneRowRelation[]
+
+
+-- !query 29
+explain select 1 - 2 || 'b'
+-- !query 29 schema
+struct<plan:string>
+-- !query 29 output
+== Physical Plan ==
+*Project [-1b AS concat(CAST((1 - 2) AS STRING), b)#x]
++- Scan OneRowRelation[]
+
+
+-- !query 30
+explain select 2 * 4  + 3 || 'b'
+-- !query 30 schema
+struct<plan:string>
+-- !query 30 output
+== Physical Plan ==
+*Project [11b AS concat(CAST(((2 * 4) + 3) AS STRING), b)#x]
++- Scan OneRowRelation[]
+
+
+-- !query 31
+explain select 3 + 1 || 'a' || 4 / 2
+-- !query 31 schema
+struct<plan:string>
+-- !query 31 output
+== Physical Plan ==
+*Project [4a2.0 AS concat(concat(CAST((3 + 1) AS STRING), a), CAST((CAST(4 AS DOUBLE) / CAST(2 AS DOUBLE)) AS STRING))#x]
++- Scan OneRowRelation[]
+
+
+-- !query 32
+explain select 1 == 1 OR 'a' || 'b' ==  'ab'
+-- !query 32 schema
+struct<plan:string>
+-- !query 32 output
+== Physical Plan ==
+*Project [true AS ((1 = 1) OR (concat(a, b) = ab))#x]
++- Scan OneRowRelation[]
+
+
+-- !query 33
+explain select 'a' || 'c' == 'ac' AND 2 == 3
+-- !query 33 schema
+struct<plan:string>
+-- !query 33 output
+== Physical Plan ==
+*Project [false AS ((concat(a, c) = ac) AND (2 = 3))#x]
++- Scan OneRowRelation[]

sql/core/src/test/resources/sql-tests/results/string-functions.sql.out

@@ -1,5 +1,5 @@
 -- Automatically generated by SQLQueryTestSuite
--- Number of queries: 2
+-- Number of queries: 3
 
 
 -- !query 0
@@ -18,3 +18,11 @@ struct<>
 -- !query 1 output
 org.apache.spark.sql.AnalysisException
 requirement failed: format_string() should take at least 1 argument; line 1 pos 7
+
+
+-- !query 2
+select 'a' || 'b' || 'c'
+-- !query 2 schema
+struct<concat(concat(a, b), c):string>
+-- !query 2 output
+abc

sql/core/src/test/scala/org/apache/spark/sql/execution/SparkSqlParserSuite.scala

@@ -19,9 +19,9 @@ package org.apache.spark.sql.execution
 
 import org.apache.spark.sql.SaveMode
 import org.apache.spark.sql.catalyst.{FunctionIdentifier, TableIdentifier}
-import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, UnresolvedRelation, UnresolvedStar}
+import org.apache.spark.sql.catalyst.analysis.{UnresolvedAlias, UnresolvedAttribute, UnresolvedRelation, UnresolvedStar}
 import org.apache.spark.sql.catalyst.catalog.{BucketSpec, CatalogStorageFormat, CatalogTable, CatalogTableType}
-import org.apache.spark.sql.catalyst.expressions.{Ascending, SortOrder}
+import org.apache.spark.sql.catalyst.expressions.{Ascending, Concat, SortOrder}
 import org.apache.spark.sql.catalyst.parser.ParseException
 import org.apache.spark.sql.catalyst.plans.PlanTest
 import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Project, RepartitionByExpression, Sort}
@@ -290,4 +290,15 @@ class SparkSqlParserSuite extends PlanTest {
           basePlan,
           numPartitions = newConf.numShufflePartitions)))
   }
+
+  test("pipeline concatenation") {
+    val concat = Concat(
+      Concat(UnresolvedAttribute("a") :: UnresolvedAttribute("b") :: Nil) ::
+      UnresolvedAttribute("c") ::
+      Nil
+    )
+    assertEqual(
+      "SELECT a || b || c FROM t",
+      Project(UnresolvedAlias(concat) :: Nil, UnresolvedRelation(TableIdentifier("t"))))
+  }
 }