Table alias implemented (#278)

CHANGELOG.md

@@ -7,6 +7,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 Breaking changes are annotated with ☢️.
 
+## Upcoming
+
+### Added
+
+- [#277]: A table selector can now have an alias. This in and of itself is not
+  particularly useful, but it's a building block for [multiple joins](https://github.com/neilotoole/sq/issues/12).
+
+  ```shell
+  $ sq `@sakila | .actor:a | .a.first_name`
+  ```
+
 ## [v0.39.1] - 2023-06-22
 
 ### Fixed
@@ -641,6 +652,7 @@ make working with lots of sources much easier.
 [#258]: https://github.com/neilotoole/sq/issues/258
 [#261]: https://github.com/neilotoole/sq/issues/261
 [#263]: https://github.com/neilotoole/sq/issues/263
+[#277]: https://github.com/neilotoole/sq/issues/277
 
 [v0.15.2]: https://github.com/neilotoole/sq/releases/tag/v0.15.2
 [v0.15.3]: https://github.com/neilotoole/sq/compare/v0.15.2...v0.15.3

libsq/ast/expr.go

@@ -27,6 +27,10 @@ type ExprElementNode struct {
 	exprNode *ExprNode
 }
 
+// resultColumn implements ast.ResultColumn.
+func (ex *ExprElementNode) resultColumn() {
+}
+
 // String returns a log/debug-friendly representation.
 func (ex *ExprElementNode) String() string {
 	str := nodeString(ex)

libsq/ast/func.go

@@ -19,6 +19,12 @@ type FuncNode struct {
 	proprietary bool
 }
 
+// resultColumn implements ast.ResultColumn.
+//
+// REVISIT: should ast.FuncNode implement ast.ResultColumn?
+func (fn *FuncNode) resultColumn() {
+}
+
 // FuncName returns the function name.
 func (fn *FuncNode) FuncName() string {
 	return fn.fnName

libsq/ast/node.go

@@ -70,6 +70,8 @@ type ResultColumn interface {
 
 	// Text returns the raw text of the node, e.g. ".actor" or "1*2".
 	Text() string
+
+	resultColumn()
 }
 
 // baseNode is a base implementation of Node.

libsq/ast/render/fromtable.go

@@ -5,12 +5,21 @@ import (
 	"github.com/neilotoole/sq/libsq/core/errz"
 )
 
+// doFromTable renders a table selector to SQL.
+//
+//	.actor    -->  FROM "actor"
+//	.actor:a  -->  FROM "actor" "a"
 func doFromTable(rc *Context, tblSel *ast.TblSelectorNode) (string, error) {
-	tblName, _ := tblSel.SelValue()
+	tblName := tblSel.TblName()
 	if tblName == "" {
 		return "", errz.Errorf("selector has empty table name: {%s}", tblSel.Text())
 	}
 
-	clause := "FROM " + rc.Dialect.Enquote(tblSel.TblName())
+	clause := "FROM " + rc.Dialect.Enquote(tblName)
+	alias := tblSel.Alias()
+	if alias != "" {
+		clause += " " + rc.Dialect.Enquote(alias)
+	}
+
 	return clause, nil
 }

libsq/ast/selector.go

@@ -146,34 +146,39 @@ func newTblSelector(selNode *SelectorNode) (*TblSelectorNode, error) { //nolint:
 }
 
 // TblName returns the table name. This is the raw value without punctuation.
-func (s *TblSelectorNode) TblName() string {
+func (n *TblSelectorNode) TblName() string {
-	return s.tblName
+	return n.tblName
+}
+
+// Alias returns the node's alias, or empty string.
+func (n *TblSelectorNode) Alias() string {
+	return n.alias
 }
 
 // Handle returns the handle, which may be empty.
-func (s *TblSelectorNode) Handle() string {
+func (n *TblSelectorNode) Handle() string {
-	return s.handle
+	return n.handle
 }
 
 // Tabler implements the Tabler marker interface.
-func (s *TblSelectorNode) tabler() {
+func (n *TblSelectorNode) tabler() {
 	// no-op
 }
 
 // SelValue returns the table name.
 // TODO: Can we get rid of this method SelValue?
-func (s *TblSelectorNode) SelValue() (string, error) {
+func (n *TblSelectorNode) SelValue() (string, error) {
-	return s.TblName(), nil
+	return n.TblName(), nil
 }
 
 // String returns a log/debug-friendly representation.
-func (s *TblSelectorNode) String() string {
+func (n *TblSelectorNode) String() string {
-	text := nodeString(s)
+	text := nodeString(n)
-	selVal, err := s.SelValue()
+	selVal, err := n.SelValue()
 	if err != nil {
 		selVal = "error: " + err.Error()
 	}
-	text += fmt.Sprintf(" | table: {%s} | datasource: {%s}", selVal, s.Handle())
+	text += fmt.Sprintf(" | table: {%s} | datasource: {%s}", selVal, n.Handle())
 	return text
 }
 
@@ -190,6 +195,10 @@ type TblColSelectorNode struct {
 	colName string
 }
 
+// resultColumn implements ast.ResultColumn.
+func (n *TblColSelectorNode) resultColumn() {
+}
+
 // IsColumn implements ResultColumn.
 func (n *TblColSelectorNode) IsColumn() bool {
 	return true
@@ -253,6 +262,10 @@ type ColSelectorNode struct {
 	colName string
 }
 
+// resultColumn implements ast.ResultColumn.
+func (n *ColSelectorNode) resultColumn() {
+}
+
 // newColSelectorNode returns a ColSelectorNode constructed from ctx.
 func newColSelectorNode(selNode *SelectorNode) (*ColSelectorNode, error) { //nolint:unparam
 	n := &ColSelectorNode{SelectorNode: selNode}

libsq/engine.go

@@ -176,10 +176,10 @@ func (ng *engine) prepareNoTabler(ctx context.Context, qm *queryModel) error {
 	return nil
 }
 
-// buildTableFromClause builds the "FROM table" fragment.
+// prepareFromTable builds the "FROM table" fragment.
 //
 // When this function returns, ng.rc will be set.
-func (ng *engine) buildTableFromClause(ctx context.Context, tblSel *ast.TblSelectorNode) (fromClause string,
+func (ng *engine) prepareFromTable(ctx context.Context, tblSel *ast.TblSelectorNode) (fromClause string,
 	fromConn driver.Database, err error,
 ) {
 	handle := tblSel.Handle()
@@ -215,10 +215,10 @@ func (ng *engine) buildTableFromClause(ctx context.Context, tblSel *ast.TblSelec
 	return fromClause, fromConn, nil
 }
 
-// buildJoinFromClause builds the "JOIN" clause.
+// prepareFromJoin builds the "JOIN" clause.
 //
 // When this function returns, ng.rc will be set.
-func (ng *engine) buildJoinFromClause(ctx context.Context, fnJoin *ast.JoinNode) (fromClause string,
+func (ng *engine) prepareFromJoin(ctx context.Context, fnJoin *ast.JoinNode) (fromClause string,
 	fromConn driver.Database, err error,
 ) {
 	if fnJoin.LeftTbl() == nil || fnJoin.LeftTbl().TblName() == "" {
@@ -230,16 +230,16 @@ func (ng *engine) buildJoinFromClause(ctx context.Context, fnJoin *ast.JoinNode)
 	}
 
 	if fnJoin.LeftTbl().Handle() != fnJoin.RightTbl().Handle() {
-		return ng.crossSourceJoin(ctx, fnJoin)
+		return ng.joinCrossSource(ctx, fnJoin)
 	}
 
-	return ng.singleSourceJoin(ctx, fnJoin)
+	return ng.joinSingleSource(ctx, fnJoin)
 }
 
-// singleSourceJoin sets up a join against a single source.
+// joinSingleSource sets up a join against a single source.
 //
 // On return, ng.rc will be set.
-func (ng *engine) singleSourceJoin(ctx context.Context, fnJoin *ast.JoinNode) (fromClause string,
+func (ng *engine) joinSingleSource(ctx context.Context, fnJoin *ast.JoinNode) (fromClause string,
 	fromDB driver.Database, err error,
 ) {
 	src, err := ng.qc.Collection.Get(fnJoin.LeftTbl().Handle())
@@ -267,11 +267,11 @@ func (ng *engine) singleSourceJoin(ctx context.Context, fnJoin *ast.JoinNode) (f
 	return fromClause, fromDB, nil
 }
 
-// crossSourceJoin returns a FROM clause that forms part of
+// joinCrossSource returns a FROM clause that forms part of
 // the SQL SELECT statement against fromDB.
 //
 // On return, ng.rc will be set.
-func (ng *engine) crossSourceJoin(ctx context.Context, fnJoin *ast.JoinNode) (fromClause string, fromDB driver.Database,
+func (ng *engine) joinCrossSource(ctx context.Context, fnJoin *ast.JoinNode) (fromClause string, fromDB driver.Database,
 	err error,
 ) {
 	leftTblName, rightTblName := fnJoin.LeftTbl().TblName(), fnJoin.RightTbl().TblName()

libsq/prepare.go

@@ -26,13 +26,12 @@ func (ng *engine) prepare(ctx context.Context, qm *queryModel) error {
 		if err = ng.prepareNoTabler(ctx, qm); err != nil {
 			return err
 		}
-
 	case *ast.TblSelectorNode:
-		if frags.From, ng.targetDB, err = ng.buildTableFromClause(ctx, node); err != nil {
+		if frags.From, ng.targetDB, err = ng.prepareFromTable(ctx, node); err != nil {
 			return err
 		}
 	case *ast.JoinNode:
-		if frags.From, ng.targetDB, err = ng.buildJoinFromClause(ctx, node); err != nil {
+		if frags.From, ng.targetDB, err = ng.prepareFromJoin(ctx, node); err != nil {
 			return err
 		}
 	default:

libsq/query_join_test.go

@@ -3,6 +3,8 @@ package libsq_test
 import (
 	"testing"
 
+	"github.com/neilotoole/sq/testh/tutil"
+
 	"github.com/neilotoole/sq/testh/sakila"
 
 	"github.com/neilotoole/sq/drivers/mysql"
@@ -10,6 +12,59 @@ import (
 	_ "github.com/mattn/go-sqlite3"
 )
 
+//nolint:exhaustive
+func TestQuery_table_alias(t *testing.T) {
+	testCases := []queryTestCase{
+		{
+			name:         "table-alias",
+			in:           `@sakila | .actor:a | .a.first_name`,
+			wantSQL:      `SELECT "a"."first_name" FROM "actor" "a"`,
+			override:     driverMap{mysql.Type: "SELECT `a`.`first_name` FROM `actor` `a`"},
+			wantRecCount: sakila.TblActorCount,
+			sinkFns: []SinkTestFunc{
+				assertSinkColName(0, "first_name"),
+			},
+		},
+		{
+			name:         "table-whitespace-alias",
+			in:           `@sakila | .actor:"oy vey" | ."oy vey".first_name`,
+			wantSQL:      `SELECT "oy vey"."first_name" FROM "actor" "oy vey"`,
+			override:     driverMap{mysql.Type: "SELECT `oy vey`.`first_name` FROM `actor` `oy vey`"},
+			wantRecCount: sakila.TblActorCount,
+			sinkFns: []SinkTestFunc{
+				assertSinkColName(0, "first_name"),
+			},
+		},
+		{
+			name:         "table-whitespace-alias-with-col-alias",
+			in:           `@sakila | .actor:"oy vey" | ."oy vey".first_name:given_name`,
+			wantSQL:      `SELECT "oy vey"."first_name" AS "given_name" FROM "actor" "oy vey"`,
+			override:     driverMap{mysql.Type: "SELECT `oy vey`.`first_name` AS `given_name` FROM `actor` `oy vey`"},
+			wantRecCount: sakila.TblActorCount,
+			sinkFns: []SinkTestFunc{
+				assertSinkColName(0, "given_name"),
+			},
+		},
+		{
+			name:         "table-whitespace-alias-with-col-whitespace-alias",
+			in:           `@sakila | .actor:"oy vey" | ."oy vey".first_name:"oy vey"`,
+			wantSQL:      `SELECT "oy vey"."first_name" AS "oy vey" FROM "actor" "oy vey"`,
+			override:     driverMap{mysql.Type: "SELECT `oy vey`.`first_name` AS `oy vey` FROM `actor` `oy vey`"},
+			wantRecCount: sakila.TblActorCount,
+			sinkFns: []SinkTestFunc{
+				assertSinkColName(0, "oy vey"),
+			},
+		},
+	}
+
+	for i, tc := range testCases {
+		tc := tc
+		t.Run(tutil.Name(i, tc.name), func(t *testing.T) {
+			execQueryTestCase(t, tc)
+		})
+	}
+}
+
 //nolint:exhaustive,lll
 func TestQuery_join(t *testing.T) {
 	testCases := []queryTestCase{

libsq/query_test.go

@@ -81,7 +81,6 @@ func execQueryTestCase(t *testing.T, tc queryTestCase) {
 	t.Helper()
 
 	coll := testh.New(t).NewCollection(sakila.SQLLatest()...)
-	// coll := testh.New(t).NewCollection(sakila.Pg)
 
 	for _, src := range coll.Sources() {
 		src := src
@@ -153,7 +152,7 @@ func assertSinkColValue(colIndex int, val any) SinkTestFunc {
 
 // assertSinkColValue returns a SinkTestFunc that asserts that
 // the name of column colIndex matches name.
-func assertSinkColName(colIndex int, name string) SinkTestFunc {
+func assertSinkColName(colIndex int, name string) SinkTestFunc { //nolint:unparam
 	return func(t testing.TB, sink *testh.RecordSink) {
 		assert.Equal(t, name, sink.RecMeta[colIndex].Name(), "column %d", colIndex)
 	}