Add support for binary expressions, filtering via WHERE (eatonphil#3)

* Start support for binary expressions

* Everything building, tests passing

* Gofmt

* Filtering generally working

* Update readme, add tablewriter library

* Add readline support

* Add makefile and more info to readme

Makefile

@@ -0,0 +1,5 @@
+fmt:
+	gofmt -w -s .
+
+test:
+	go test -race .

README.md

@@ -1,6 +1,6 @@
 # gosql
 
-An early PostgreSQL implementation in Go (WIP)
+An early PostgreSQL implementation in Go.
 
 ## Example
 
@@ -9,21 +9,67 @@ $ git clone [email protected]:eatonphil/gosql
 $ cd gosql
 $ go run cmd/main.go
 Welcome to gosql.
-# CREATE TABLE users (id INT, name TEXT);
+# CREATE TABLE users (name TEXT, age INT);
 ok
-# INSERT INTO users VALUES (1, 'Phil');
+#  INSERT INTO users VALUES ('Stephen', 16);
 ok
-# SELECT id, name FROM users;
-| id | name |
-====================
-| 1 |  Phil |
+# SELECT name, age FROM users;
+   name   | age
+----------+------
+  Stephen |  16
+(1 result)
 ok
-# INSERT INTO users VALUES (2, 'Kate');
+# INSERT INTO users VALUES ('Adrienne', 23);
 ok
-# SELECT name, id FROM users;
-| name | id |
-====================
-| Phil |  1 |
-| Kate |  2 |
+# SELECT age + 2, name FROM users WHERE age = 23;
+  age |   name
+------+-----------
+   25 | Adrienne
+(1 result)
+ok
+# SELECT name FROM users;
+    name
+------------
+  Stephen
+  Adrienne
+(2 results)
 ok
 ```
+
+## Architecture
+
+* [cmd/main.go](./cmd/main.go)
+  * Contains the REPL and high-level interface to the project
+  * Dataflow is: user input -> lexer -> parser -> in-memory backend
+* [lexer.go](./lexer.go)
+  * Handles breaking user input into tokens for the parser
+* [parser.go](./parser.go)
+  * Matches a list of tokens into an AST or fails if the user input is not a valid program
+* [memory.go](./memory.go)
+  * An example, in-memory backend supporting the Backend interface (defined in backend.go)
+
+## Contributing
+
+* Add a new operator (such as `<`, `>`, etc.) supported by PostgreSQL
+* Add a new data type supported by PostgreSQL
+
+In each case, you'll probably have to add support in the lexer,
+parser, and in-memory backend. I recommend going in that order.
+
+In all cases, make sure the code is formatted (`make fmt`) and passes
+tests (`make test`). New code should have tests.
+
+## Blog series
+
+* [https://notes.eatonphil.com/database-basics.html](Writing a SQL database from scratch in Go)
+
+## Further reading
+
+Here are some similar projects written in Go.
+
+* [go-mysql-server](https://github.com/src-d/go-mysql-server)
+  * This is a MySQL frontend (with an in-memory backend for testing only).
+* [ramsql](https://github.com/proullon/ramsql)
+  * This is a WIP PostgreSQL-compatible in-memory database.
+* [CockroachDB](https://github.com/cockroachdb/cockroach)
+  * This is a production-ready PostgreSQL-compatible database.

ast.go

@@ -4,10 +4,18 @@ type expressionKind uint
 
 const (
 	literalKind expressionKind = iota
+	binaryKind
 )
 
+type binaryExpression struct {
+	a  expression
+	b  expression
+	op token
+}
+
 type expression struct {
 	literal *token
+	binary  *binaryExpression
 	kind    expressionKind
 }
 
@@ -24,8 +32,9 @@ type fromItem struct {
 }
 
 type SelectStatement struct {
-	item *[]*selectItem
-	from *fromItem
+	item  *[]*selectItem
+	from  *fromItem
+	where *expression
 }
 
 type columnDefinition struct {

interface.go → backend.go

@@ -5,11 +5,13 @@ type ColumnType uint
 const (
 	TextType ColumnType = iota
 	IntType
+	BoolType
 )
 
 type Cell interface {
 	AsText() string
 	AsInt() int32
+	AsBool() bool
 }
 
 type Results struct {

cmd/main.go

@@ -1,81 +1,134 @@
 package main
 
 import (
-	"bufio"
 	"fmt"
+	"io"
 	"os"
-	"strings"
 
 	"github.com/eatonphil/gosql"
+
+	"github.com/chzyer/readline"
+	"github.com/olekukonko/tablewriter"
 )
 
+func doSelect(mb gosql.Backend, slct *gosql.SelectStatement) error {
+	results, err := mb.Select(slct)
+	if err != nil {
+		return err
+	}
+
+	if len(results.Rows) == 0 {
+		fmt.Println("(no results)")
+		return nil
+	}
+
+	table := tablewriter.NewWriter(os.Stdout)
+	header := []string{}
+	for _, col := range results.Columns {
+		header = append(header, col.Name)
+	}
+	table.SetHeader(header)
+	table.SetAutoFormatHeaders(false)
+
+	rows := [][]string{}
+	for _, result := range results.Rows {
+		row := []string{}
+		for i, cell := range result {
+			typ := results.Columns[i].Type
+			s := ""
+			switch typ {
+			case gosql.IntType:
+				s = fmt.Sprintf("%d", cell.AsInt())
+			case gosql.TextType:
+				s = cell.AsText()
+			case gosql.BoolType:
+				s = "true"
+				if !cell.AsBool() {
+					s = "false"
+				}
+			}
+
+			row = append(row, s)
+		}
+
+		rows = append(rows, row)
+	}
+
+	table.SetBorder(false)
+	table.AppendBulk(rows)
+	table.Render()
+
+	if len(rows) == 1 {
+		fmt.Println("(1 result)")
+	} else {
+		fmt.Printf("(%d results)\n", len(rows))
+	}
+
+	return nil
+}
+
 func main() {
 	mb := gosql.NewMemoryBackend()
 
-	reader := bufio.NewReader(os.Stdin)
+	l, err := readline.NewEx(&readline.Config{
+		Prompt:          "# ",
+		HistoryFile:     "/tmp/gosql.tmp",
+		InterruptPrompt: "^C",
+		EOFPrompt:       "exit",
+	})
+	if err != nil {
+		panic(err)
+	}
+	defer l.Close()
+
 	fmt.Println("Welcome to gosql.")
+repl:
 	for {
 		fmt.Print("# ")
-		text, err := reader.ReadString('\n')
-		text = strings.Replace(text, "\n", "", -1)
+		line, err := l.Readline()
+		if err == readline.ErrInterrupt {
+			if len(line) == 0 {
+				break
+			} else {
+				continue repl
+			}
+		} else if err == io.EOF {
+			break
+		}
+		if err != nil {
+			fmt.Println("Error while reading line:", err)
+			continue repl
+		}
 
-		ast, err := gosql.Parse(text)
+		ast, err := gosql.Parse(line)
 		if err != nil {
-			panic(err)
+			fmt.Println("Error while parsing:", err)
+			continue repl
 		}
 
 		for _, stmt := range ast.Statements {
 			switch stmt.Kind {
 			case gosql.CreateTableKind:
 				err = mb.CreateTable(ast.Statements[0].CreateTableStatement)
 				if err != nil {
-					panic(err)
+					fmt.Println("Error creating table", err)
+					continue repl
 				}
-				fmt.Println("ok")
 			case gosql.InsertKind:
 				err = mb.Insert(stmt.InsertStatement)
 				if err != nil {
-					panic(err)
+					fmt.Println("Error inserting values:", err)
+					continue repl
 				}
-
-				fmt.Println("ok")
 			case gosql.SelectKind:
-				results, err := mb.Select(stmt.SelectStatement)
+				err := doSelect(mb, stmt.SelectStatement)
 				if err != nil {
-					panic(err)
-				}
-
-				for _, col := range results.Columns {
-					fmt.Printf("| %s ", col.Name)
+					fmt.Println("Error selecting values:", err)
+					continue repl
 				}
-				fmt.Println("|")
-
-				for i := 0; i < 20; i++ {
-					fmt.Printf("=")
-				}
-				fmt.Println()
-
-				for _, result := range results.Rows {
-					fmt.Printf("|")
-
-					for i, cell := range result {
-						typ := results.Columns[i].Type
-						s := ""
-						switch typ {
-						case gosql.IntType:
-							s = fmt.Sprintf("%d", cell.AsInt())
-						case gosql.TextType:
-							s = cell.AsText()
-						}
-
-						fmt.Printf(" %s | ", s)
-					}
-
-					fmt.Println()
-				}
-
-				fmt.Println("ok")
 			}
 		}
+
+		fmt.Println("ok")
 	}
 }

error.go

@@ -8,4 +8,6 @@ var (
 	ErrInvalidSelectItem  = errors.New("Select item is not valid")
 	ErrInvalidDatatype    = errors.New("Invalid datatype")
 	ErrMissingValues      = errors.New("Missing values")
+	ErrInvalidCell        = errors.New("Cell is invalid")
+	ErrInvalidOperands    = errors.New("Operands are invalid")
 )

go.mod

@@ -2,4 +2,10 @@ module github.com/eatonphil/gosql
 
 go 1.13
 
-require github.com/stretchr/testify v1.5.1
+require (
+	github.com/chzyer/logex v1.1.10 // indirect
+	github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e
+	github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1 // indirect
+	github.com/olekukonko/tablewriter v0.0.4
+	github.com/stretchr/testify v1.5.1
+)

go.sum

@@ -1,5 +1,15 @@
+github.com/chzyer/logex v1.1.10 h1:Swpa1K6QvQznwJRcfTfQJmTE72DqScAa40E+fbHEXEE=
+github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e h1:fY5BOSpyZCqRo5OhCuC+XN+r/bBCmeuuJtjz+bCNIf8=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1 h1:q763qf9huN11kDQavWsoZXJNW3xEE4JJyHa5Q25/sd8=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/mattn/go-runewidth v0.0.7 h1:Ei8KR0497xHyKJPAv59M1dkC+rOZCMBJ+t3fZ+twI54=
+github.com/mattn/go-runewidth v0.0.7/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
+github.com/olekukonko/tablewriter v0.0.4 h1:vHD/YYe1Wolo78koG299f7V/VAS08c6IpCLn+Ejf/w8=
+github.com/olekukonko/tablewriter v0.0.4/go.mod h1:zq6QwlOf5SlnkVbMSr5EoBv3636FWnp+qbPhuoO21uA=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=