Fixing Column aliases in outer join queries (#15384)

Signed-off-by: Manan Gupta <manan@planetscale.com>
Signed-off-by: Florent Poinsard <35779988+frouioui@users.noreply.github.com>
Co-authored-by: Florent Poinsard <35779988+frouioui@users.noreply.github.com>

go/test/endtoend/vtgate/queries/misc/misc_test.go

@@ -352,3 +352,22 @@ func TestTransactionModeVar(t *testing.T) {
  })
  }
 }
+
+// TestAliasesInOuterJoinQueries tests that aliases work in queries that have outer join clauses.
+func TestAliasesInOuterJoinQueries(t *testing.T) {
+ utils.SkipIfBinaryIsBelowVersion(t, 20, "vtgate")
+
+ mcmp, closer := start(t)
+ defer closer()
+
+ // Insert data into the 2 tables
+ mcmp.Exec("insert into t1(id1, id2) values (1,2), (42,5), (5, 42)")
+ mcmp.Exec("insert into tbl(id, unq_col, nonunq_col) values (1,2,3), (2,5,3), (3, 42, 2)")
+
+ // Check that the select query works as intended and then run it again verifying the column names as well.
+ mcmp.AssertMatches("select t1.id1 as t0, t1.id1 as t1, tbl.unq_col as col from t1 left outer join tbl on t1.id2 = tbl.nonunq_col", `[[INT64(1) INT64(1) INT64(42)] [INT64(5) INT64(5) NULL] [INT64(42) INT64(42) NULL]]`)
+ mcmp.ExecWithColumnCompare("select t1.id1 as t0, t1.id1 as t1, tbl.unq_col as col from t1 left outer join tbl on t1.id2 = tbl.nonunq_col")
+
+ mcmp.AssertMatches("select t1.id1 as t0, t1.id1 as t1, tbl.unq_col as col from t1 left outer join tbl on t1.id2 = tbl.nonunq_col order by t1.id2 limit 2", `[[INT64(1) INT64(1) INT64(42)] [INT64(42) INT64(42) NULL]]`)
+ mcmp.ExecWithColumnCompare("select t1.id1 as t0, t1.id1 as t1, tbl.unq_col as col from t1 left outer join tbl on t1.id2 = tbl.nonunq_col order by t1.id2 limit 2")
+}

go/vt/vtgate/engine/simple_projection.go

@@ -19,6 +19,8 @@ package engine
 import (
  "context"
 
+ "google.golang.org/protobuf/proto"
+
  "vitess.io/vitess/go/sqltypes"
  querypb "vitess.io/vitess/go/vt/proto/query"
 )
@@ -29,8 +31,10 @@ var _ Primitive = (*SimpleProjection)(nil)
 type SimpleProjection struct {
  // Cols defines the column numbers from the underlying primitive
  // to be returned.
- Cols []int
- Input Primitive
+ Cols []int
+ // ColNames are the column names to use for the columns.
+ ColNames []string
+ Input Primitive
 }
 
 // NeedsTransaction implements the Primitive interface
@@ -104,8 +108,13 @@ func (sc *SimpleProjection) buildFields(inner *sqltypes.Result) []*querypb.Field
  return nil
  }
  fields := make([]*querypb.Field, 0, len(sc.Cols))
- for _, col := range sc.Cols {
- fields = append(fields, inner.Fields[col])
+ for idx, col := range sc.Cols {
+ field := inner.Fields[col]
+ if sc.ColNames[idx] != "" {
+ field = proto.Clone(field).(*querypb.Field)
+ field.Name = sc.ColNames[idx]
+ }
+ fields = append(fields, field)
  }
  return fields
 }
@@ -114,6 +123,16 @@ func (sc *SimpleProjection) description() PrimitiveDescription {
  other := map[string]any{
  "Columns": sc.Cols,
  }
+ emptyColNames := true
+ for _, cName := range sc.ColNames {
+ if cName != "" {
+ emptyColNames = false
+ break
+ }
+ }
+ if !emptyColNames {
+ other["ColumnNames"] = sc.ColNames
+ }
  return PrimitiveDescription{
  OperatorType: "SimpleProjection",
  Other: other,

go/vt/vtgate/engine/simple_projection_test.go

@@ -44,8 +44,9 @@ func TestSubqueryExecute(t *testing.T) {
  }
 
  sq := &SimpleProjection{
- Cols: []int{0, 2},
- Input: prim,
+ Cols: []int{0, 2},
+ ColNames: []string{"", ""},
+ Input: prim,
  }
 
  bv := map[string]*querypb.BindVariable{
@@ -93,8 +94,9 @@ func TestSubqueryStreamExecute(t *testing.T) {
  }
 
  sq := &SimpleProjection{
- Cols: []int{0, 2},
- Input: prim,
+ Cols: []int{0, 2},
+ ColNames: []string{"", ""},
+ Input: prim,
  }
 
  bv := map[string]*querypb.BindVariable{
@@ -142,8 +144,9 @@ func TestSubqueryGetFields(t *testing.T) {
  }
 
  sq := &SimpleProjection{
- Cols: []int{0, 2},
- Input: prim,
+ Cols: []int{0, 2},
+ ColNames: []string{"", ""},
+ Input: prim,
  }
 
  bv := map[string]*querypb.BindVariable{

go/vt/vtgate/planbuilder/operator_transformers.go

@@ -355,10 +355,10 @@ func transformProjection(ctx *plancontext.PlanningContext, op *operators.Project
  return nil, err
  }
 
- if cols := op.AllOffsets(); cols != nil {
+ if cols, colNames := op.AllOffsets(); cols != nil {
  // if all this op is doing is passing through columns from the input, we
  // can use the faster SimpleProjection
- return useSimpleProjection(ctx, op, cols, src)
+ return useSimpleProjection(ctx, op, cols, colNames, src)
  }
 
  ap, err := op.GetAliasedProjections()
@@ -403,7 +403,7 @@ func getEvalEngingeExpr(ctx *plancontext.PlanningContext, pe *operators.ProjExpr
 
 // useSimpleProjection uses nothing at all if the output is already correct,
 // or SimpleProjection when we have to reorder or truncate the columns
-func useSimpleProjection(ctx *plancontext.PlanningContext, op *operators.Projection, cols []int, src logicalPlan) (logicalPlan, error) {
+func useSimpleProjection(ctx *plancontext.PlanningContext, op *operators.Projection, cols []int, colNames []string, src logicalPlan) (logicalPlan, error) {
  columns := op.Source.GetColumns(ctx)
  if len(columns) == len(cols) && elementsMatchIndices(cols) {
  // the columns are already in the right order. we don't need anything at all here
@@ -412,7 +412,8 @@ func useSimpleProjection(ctx *plancontext.PlanningContext, op *operators.Project
  return &simpleProjection{
  logicalPlanCommon: newBuilderCommon(src),
  eSimpleProj: &engine.SimpleProjection{
- Cols: cols,
+ Cols: cols,
+ ColNames: colNames,
  },
  }, nil
 }

go/vt/vtgate/planbuilder/operators/projection.go

@@ -399,18 +399,23 @@ func (p *Projection) GetOrdering(ctx *plancontext.PlanningContext) []OrderBy {
 
 // AllOffsets returns a slice of integer offsets for all columns in the Projection
 // if all columns are of type Offset. If any column is not of type Offset, it returns nil.
-func (p *Projection) AllOffsets() (cols []int) {
+func (p *Projection) AllOffsets() (cols []int, colNames []string) {
  ap, err := p.GetAliasedProjections()
  if err != nil {
- return nil
+ return nil, nil
  }
  for _, c := range ap {
  offset, ok := c.Info.(Offset)
  if !ok {
- return nil
+ return nil, nil
+ }
+ colName := ""
+ if c.Original.As.NotEmpty() {
+ colName = c.Original.As.String()
  }
 
  cols = append(cols, int(offset))
+ colNames = append(colNames, colName)
  }
  return
 }
@@ -445,7 +450,7 @@ func (p *Projection) Compact(ctx *plancontext.PlanningContext) (Operator, *Apply
  needed := false
  for i, projection := range ap {
  e, ok := projection.Info.(Offset)
- if !ok || int(e) != i {
+ if !ok || int(e) != i || projection.Original.As.NotEmpty() {
  needed = true
  break
  }
@@ -475,6 +480,9 @@ func (p *Projection) compactWithJoin(ctx *plancontext.PlanningContext, join *App
  for _, col := range ap {
  switch colInfo := col.Info.(type) {
  case Offset:
+ if col.Original.As.NotEmpty() {
+ return p, NoRewrite
+ }
  newColumns = append(newColumns, join.Columns[colInfo])
  newColumnsAST.add(join.JoinColumns.columns[colInfo])
  case nil:

go/vt/vtgate/planbuilder/testdata/ddl_cases_no_default_keyspace.json

@@ -144,7 +144,7 @@
  "Name": "user",
  "Sharded": true
  },
- "Query": "create view view_a as select a.user_id as user_id, a.col1 as col1, a.col2 as col2, b.user_id as user_id, b.col1 as col1, b.col2 as col2 from authoritative as a join authoritative as b on a.user_id = b.user_id"
+ "Query": "create view view_a as select a.user_id, a.col1, a.col2, b.user_id, b.col1, b.col2 from authoritative as a join authoritative as b on a.user_id = b.user_id"
  },
  "TablesUsed": [
  "user.view_a"
@@ -201,7 +201,7 @@
  "Name": "user",
  "Sharded": true
  },
- "Query": "create view view_a as select `user`.id, a.user_id as user_id, a.col1 as col1, a.col2 as col2, `user`.col1 from authoritative as a join `user` on a.user_id = `user`.id"
+ "Query": "create view view_a as select `user`.id, a.user_id, a.col1, a.col2, `user`.col1 from authoritative as a join `user` on a.user_id = `user`.id"
  },
  "TablesUsed": [
  "user.view_a"

go/vt/vtgate/planbuilder/testdata/from_cases.json

@@ -3760,8 +3760,8 @@
  "Name": "user",
  "Sharded": true
  },
- "FieldQuery": "select authoritative.col1 as col1, authoritative.user_id as user_id, authoritative.col2 as col2 from authoritative where 1 != 1",
- "Query": "select authoritative.col1 as col1, authoritative.user_id as user_id, authoritative.col2 as col2 from authoritative",
+ "FieldQuery": "select authoritative.col1, authoritative.user_id, authoritative.col2 from authoritative where 1 != 1",
+ "Query": "select authoritative.col1, authoritative.user_id, authoritative.col2 from authoritative",
  "Table": "authoritative"
  },
  {
@@ -3771,8 +3771,8 @@
  "Name": "main",
  "Sharded": false
  },
- "FieldQuery": "select unsharded_authoritative.col2 as col2 from unsharded_authoritative where 1 != 1",
- "Query": "select unsharded_authoritative.col2 as col2 from unsharded_authoritative where unsharded_authoritative.col1 = :authoritative_col1",
+ "FieldQuery": "select unsharded_authoritative.col2 from unsharded_authoritative where 1 != 1",
+ "Query": "select unsharded_authoritative.col2 from unsharded_authoritative where unsharded_authoritative.col1 = :authoritative_col1",
  "Table": "unsharded_authoritative"
  }
  ]

go/vt/vtgate/planbuilder/testdata/info_schema57_cases.json

@@ -750,8 +750,8 @@
  "Name": "main",
  "Sharded": false
  },
- "FieldQuery": "select a.VARIABLE_NAME as VARIABLE_NAME, a.VARIABLE_VALUE as VARIABLE_VALUE, b.CHARACTER_SET_NAME as CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME as DEFAULT_COLLATE_NAME, b.DESCRIPTION as DESCRIPTION, b.MAXLEN as MAXLEN from information_schema.GLOBAL_STATUS as a, information_schema.CHARACTER_SETS as b where 1 != 1",
- "Query": "select a.VARIABLE_NAME as VARIABLE_NAME, a.VARIABLE_VALUE as VARIABLE_VALUE, b.CHARACTER_SET_NAME as CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME as DEFAULT_COLLATE_NAME, b.DESCRIPTION as DESCRIPTION, b.MAXLEN as MAXLEN from information_schema.GLOBAL_STATUS as a, information_schema.CHARACTER_SETS as b",
+ "FieldQuery": "select a.VARIABLE_NAME, a.VARIABLE_VALUE, b.CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME, b.DESCRIPTION, b.MAXLEN from information_schema.GLOBAL_STATUS as a, information_schema.CHARACTER_SETS as b where 1 != 1",
+ "Query": "select a.VARIABLE_NAME, a.VARIABLE_VALUE, b.CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME, b.DESCRIPTION, b.MAXLEN from information_schema.GLOBAL_STATUS as a, information_schema.CHARACTER_SETS as b",
  "Table": "information_schema.CHARACTER_SETS, information_schema.GLOBAL_STATUS"
  }
  }

go/vt/vtgate/planbuilder/testdata/info_schema80_cases.json

@@ -815,8 +815,8 @@
  "Name": "main",
  "Sharded": false
  },
- "FieldQuery": "select a.CONSTRAINT_CATALOG as CONSTRAINT_CATALOG, a.CONSTRAINT_SCHEMA as CONSTRAINT_SCHEMA, a.CONSTRAINT_NAME as CONSTRAINT_NAME, a.CHECK_CLAUSE as CHECK_CLAUSE, b.CHARACTER_SET_NAME as CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME as DEFAULT_COLLATE_NAME, b.DESCRIPTION as DESCRIPTION, b.MAXLEN as MAXLEN from information_schema.CHECK_CONSTRAINTS as a, information_schema.CHARACTER_SETS as b where 1 != 1",
- "Query": "select a.CONSTRAINT_CATALOG as CONSTRAINT_CATALOG, a.CONSTRAINT_SCHEMA as CONSTRAINT_SCHEMA, a.CONSTRAINT_NAME as CONSTRAINT_NAME, a.CHECK_CLAUSE as CHECK_CLAUSE, b.CHARACTER_SET_NAME as CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME as DEFAULT_COLLATE_NAME, b.DESCRIPTION as DESCRIPTION, b.MAXLEN as MAXLEN from information_schema.CHECK_CONSTRAINTS as a, information_schema.CHARACTER_SETS as b",
+ "FieldQuery": "select a.CONSTRAINT_CATALOG, a.CONSTRAINT_SCHEMA, a.CONSTRAINT_NAME, a.CHECK_CLAUSE, b.CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME, b.DESCRIPTION, b.MAXLEN from information_schema.CHECK_CONSTRAINTS as a, information_schema.CHARACTER_SETS as b where 1 != 1",
+ "Query": "select a.CONSTRAINT_CATALOG, a.CONSTRAINT_SCHEMA, a.CONSTRAINT_NAME, a.CHECK_CLAUSE, b.CHARACTER_SET_NAME, b.DEFAULT_COLLATE_NAME, b.DESCRIPTION, b.MAXLEN from information_schema.CHECK_CONSTRAINTS as a, information_schema.CHARACTER_SETS as b",
  "Table": "information_schema.CHARACTER_SETS, information_schema.CHECK_CONSTRAINTS"
  }
  }

go/vt/vtgate/planbuilder/testdata/rails_cases.json

@@ -50,8 +50,8 @@
  "Name": "user",
  "Sharded": true
  },
- "FieldQuery": "select author5s.id as id, author5s.`name` as `name`, author5s.created_at as created_at, author5s.updated_at as updated_at, book6s.supplier5_id, book6s.id from author5s, book6s where 1 != 1",
- "Query": "select author5s.id as id, author5s.`name` as `name`, author5s.created_at as created_at, author5s.updated_at as updated_at, book6s.supplier5_id, book6s.id from author5s, book6s where book6s.author5_id = author5s.id",
+ "FieldQuery": "select author5s.id, author5s.`name`, author5s.created_at, author5s.updated_at, book6s.supplier5_id, book6s.id from author5s, book6s where 1 != 1",
+ "Query": "select author5s.id, author5s.`name`, author5s.created_at, author5s.updated_at, book6s.supplier5_id, book6s.id from author5s, book6s where book6s.author5_id = author5s.id",
  "Table": "author5s, book6s"
  },
  {

go/vt/vtgate/planbuilder/testdata/select_cases.json

@@ -361,8 +361,8 @@
  "Name": "user",
  "Sharded": true
  },
- "FieldQuery": "select a.user_id as user_id, a.col1 as col1, a.col2 as col2, b.user_id as user_id, b.col1 as col1, b.col2 as col2 from authoritative as a, authoritative as b where 1 != 1",
- "Query": "select a.user_id as user_id, a.col1 as col1, a.col2 as col2, b.user_id as user_id, b.col1 as col1, b.col2 as col2 from authoritative as a, authoritative as b where a.user_id = b.user_id",
+ "FieldQuery": "select a.user_id, a.col1, a.col2, b.user_id, b.col1, b.col2 from authoritative as a, authoritative as b where 1 != 1",
+ "Query": "select a.user_id, a.col1, a.col2, b.user_id, b.col1, b.col2 from authoritative as a, authoritative as b where a.user_id = b.user_id",
  "Table": "authoritative"
  },
  "TablesUsed": [
@@ -433,8 +433,8 @@
  "Name": "user",
  "Sharded": true
  },
- "FieldQuery": "select `user`.id, a.user_id as user_id, a.col1 as col1, a.col2 as col2, `user`.col1 from authoritative as a, `user` where 1 != 1",
- "Query": "select `user`.id, a.user_id as user_id, a.col1 as col1, a.col2 as col2, `user`.col1 from authoritative as a, `user` where a.user_id = `user`.id",
+ "FieldQuery": "select `user`.id, a.user_id, a.col1, a.col2, `user`.col1 from authoritative as a, `user` where 1 != 1",
+ "Query": "select `user`.id, a.user_id, a.col1, a.col2, `user`.col1 from authoritative as a, `user` where a.user_id = `user`.id",
  "Table": "`user`, authoritative"
  },
  "TablesUsed": [
@@ -4997,5 +4997,63 @@
  "user.user"
  ]
  }
+ },
+ {
+ "comment": "column name aliases in outer join queries",
+ "query": "select name as t0, name as t1 from user left outer join user_extra on user.cola = user_extra.cola",
+ "plan": {
+ "QueryType": "SELECT",
+ "Original": "select name as t0, name as t1 from user left outer join user_extra on user.cola = user_extra.cola",
+ "Instructions": {
+ "OperatorType": "SimpleProjection",
+ "ColumnNames": [
+ "t0",
+ "t1"
+ ],
+ "Columns": [
+ 0,
+ 0
+ ],
+ "Inputs": [
+ {
+ "OperatorType": "Join",
+ "Variant": "LeftJoin",
+ "JoinColumnIndexes": "L:0",
+ "JoinVars": {
+ "user_cola": 1
+ },
+ "TableName": "`user`_user_extra",
+ "Inputs": [
+ {
+ "OperatorType": "Route",
+ "Variant": "Scatter",
+ "Keyspace": {
+ "Name": "user",
+ "Sharded": true
+ },
+ "FieldQuery": "select `name`, `user`.cola from `user` where 1 != 1",
+ "Query": "select `name`, `user`.cola from `user`",
+ "Table": "`user`"
+ },
+ {
+ "OperatorType": "Route",
+ "Variant": "Scatter",
+ "Keyspace": {
+ "Name": "user",
+ "Sharded": true
+ },
+ "FieldQuery": "select 1 from user_extra where 1 != 1",
+ "Query": "select 1 from user_extra where user_extra.cola = :user_cola",
+ "Table": "user_extra"
+ }
+ ]
+ }
+ ]
+ },
+ "TablesUsed": [
+ "user.user",
+ "user.user_extra"
+ ]
+ }
  }
 ]

go/vt/vtgate/semantics/early_rewriter.go

@@ -1237,17 +1237,13 @@ type expanderState struct {
 // addColumn adds columns to the expander state. If we have vschema info about the query,
 // we also store which columns were expanded
 func (e *expanderState) addColumn(col ColumnInfo, tbl TableInfo, tblName sqlparser.TableName) {
- withQualifier := e.needsQualifier
  var colName *sqlparser.ColName
  var alias sqlparser.IdentifierCI
- if withQualifier {
+ if e.needsQualifier {
  colName = sqlparser.NewColNameWithQualifier(col.Name, tblName)
  } else {
  colName = sqlparser.NewColName(col.Name)
  }
- if e.needsQualifier {
- alias = sqlparser.NewIdentifierCI(col.Name)
- }
  e.colNames = append(e.colNames, &sqlparser.AliasedExpr{Expr: colName, As: alias})
  e.storeExpandInfo(tbl, tblName, colName)
 }