Merge pull request #2 from youtube/master

merge

data/test/vtgate/postprocess_cases.txt

@@ -196,6 +196,63 @@
  }
 }
 
+# ORDER BY RAND()
+"select col from user order by RAND()"
+{
+ "Original": "select col from user order by RAND()",
+ "Instructions": {
+ "Opcode": "SelectScatter",
+ "Keyspace": {
+ "Name": "user",
+ "Sharded": true
+ },
+ "Query": "select col from user order by rand()",
+ "FieldQuery": "select col from user where 1 != 1"
+ }
+}
+
+# ORDER BY RAND() for join
+"select user.col1 as a, user.col2, music.col3 from user join music on user.id = music.id where user.id = 1 order by RAND()"
+{
+ "Original": "select user.col1 as a, user.col2, music.col3 from user join music on user.id = music.id where user.id = 1 order by RAND()",
+ "Instructions": {
+ "Opcode": "Join",
+ "Left": {
+ "Opcode": "SelectEqualUnique",
+ "Keyspace": {
+ "Name": "user",
+ "Sharded": true
+ },
+ "Query": "select user.col1 as a, user.col2, user.id from user where user.id = 1 order by rand()",
+ "FieldQuery": "select user.col1 as a, user.col2, user.id from user where 1 != 1",
+ "Vindex": "user_index",
+ "Values": [1]
+ },
+ "Right": {
+ "Opcode": "SelectEqualUnique",
+ "Keyspace": {
+ "Name": "user",
+ "Sharded": true
+ },
+ "Query": "select music.col3 from music where music.id = :user_id order by rand()",
+ "FieldQuery": "select music.col3 from music where 1 != 1",
+ "Vindex": "music_user_map",
+ "Values": [":user_id"],
+ "JoinVars": {
+ "user_id": {}
+ }
+ },
+ "Cols": [
+ -1,
+ -2,
+ 1
+ ],
+ "Vars": {
+ "user_id": 2
+ }
+ }
+}
+
 # Order by, '*' expression
 "select * from user where id = 5 order by col"
 {

go/vt/sqlparser/ast.go

@@ -2566,6 +2566,13 @@ func (node *Order) Format(buf *TrackedBuffer) {
  buf.Myprintf("%v", node)
  return
  }
+ if node, ok := node.Expr.(*FuncExpr); ok {
+ if node.Name.Lowered() == "rand" {
+ buf.Myprintf("%v", node)
+ return
+ }
+ }
+
  buf.Myprintf("%v %s", node.Expr, node.Direction)
 }
 

go/vt/vtgate/planbuilder/builder.go

@@ -73,6 +73,10 @@ type builder interface {
  // just on optimization hint.
  PushOrderByNull()
 
+ // PushOrderByRand pushes the special case ORDER BY RAND() to
+ // all primitives.
+ PushOrderByRand()
+
  // SetUpperLimit is an optimization hint that tells that primitive
  // that it does not need to return more than the specified number of rows.
  // A primitive that cannot perform this can ignore the request.

go/vt/vtgate/planbuilder/join.go

@@ -201,6 +201,12 @@ func (jb *join) PushOrderByNull() {
  jb.Right.PushOrderByNull()
 }
 
+// PushOrderByRand satisfies the builder interface.
+func (jb *join) PushOrderByRand() {
+ jb.Left.PushOrderByRand()
+ jb.Right.PushOrderByRand()
+}
+
 // SetUpperLimit satisfies the builder interface.
 // The call is ignored because results get multiplied
 // as they join with others. So, it's hard to reliably

go/vt/vtgate/planbuilder/limit.go

@@ -104,6 +104,11 @@ func (l *limit) PushOrderByNull() {
  panic("BUG: unreachable")
 }
 
+// PushOrderByRand satisfies the builder interface.
+func (l *limit) PushOrderByRand() {
+ panic("BUG: unreachable")
+}
+
 // SetLimit sets the limit for the primitive. It calls the underlying
 // primitive's SetUpperLimit, which is an optimization hint that informs
 // the underlying primitive that it doesn't need to return more rows than

go/vt/vtgate/planbuilder/ordered_aggregate.go

@@ -446,6 +446,11 @@ func (oa *orderedAggregate) PushOrderByNull() {
  panic("BUG: unreachable")
 }
 
+// PushOrderByRand satisfies the builder interface.
+func (oa *orderedAggregate) PushOrderByRand() {
+ panic("BUG: unreachable")
+}
+
 // SetUpperLimit satisfies the builder interface.
 func (oa *orderedAggregate) SetUpperLimit(count *sqlparser.SQLVal) {
  oa.input.SetUpperLimit(count)

go/vt/vtgate/planbuilder/postprocess.go

@@ -75,6 +75,11 @@ func pushOrderBy(orderBy sqlparser.OrderBy, bldr builder) error {
  if _, ok := orderBy[0].Expr.(*sqlparser.NullVal); ok {
  bldr.PushOrderByNull()
  return nil
+ } else if f, ok := orderBy[0].Expr.(*sqlparser.FuncExpr); ok {
+ if f.Name.Lowered() == "rand" {
+ bldr.PushOrderByRand()
+ return nil
+ }
  }
  }
 

go/vt/vtgate/planbuilder/route.go

@@ -450,6 +450,11 @@ func (rb *route) PushOrderByNull() {
  rb.Select.(*sqlparser.Select).OrderBy = sqlparser.OrderBy{&sqlparser.Order{Expr: &sqlparser.NullVal{}}}
 }
 
+// PushOrderByRand satisfies the builder interface.
+func (rb *route) PushOrderByRand() {
+ rb.Select.(*sqlparser.Select).OrderBy = sqlparser.OrderBy{&sqlparser.Order{Expr: &sqlparser.FuncExpr{Name: sqlparser.NewColIdent("rand")}}}
+}
+
 // SetLimit adds a LIMIT clause to the route.
 func (rb *route) SetLimit(limit *sqlparser.Limit) {
  rb.Select.SetLimit(limit)

go/vt/vtgate/planbuilder/subquery.go

@@ -140,6 +140,10 @@ func (sq *subquery) PushSelect(expr *sqlparser.AliasedExpr, _ columnOriginator)
 func (sq *subquery) PushOrderByNull() {
 }
 
+// PushOrderByRand satisfies the builder interface.
+func (sq *subquery) PushOrderByRand() {
+}
+
 // SetUpperLimit satisfies the builder interface.
 // For now, the call is ignored because the
 // repercussions of pushing this limit down

go/vt/vtgate/planbuilder/vindex_func.go

@@ -182,6 +182,10 @@ func (vf *vindexFunc) PushSelect(expr *sqlparser.AliasedExpr, _ columnOriginator
 func (vf *vindexFunc) PushOrderByNull() {
 }
 
+// PushOrderByRand satisfies the builder interface.
+func (vf *vindexFunc) PushOrderByRand() {
+}
+
 // SetUpperLimit satisfies the builder interface.
 func (vf *vindexFunc) SetUpperLimit(_ *sqlparser.SQLVal) {
 }