test: add an in-memory SQLite oracle over the same fixtures

go.mod

@@ -1,3 +1,17 @@
 module github.com/aybavs/sql-query-engine
 
-go 1.22
+go 1.25.0
+
+require modernc.org/sqlite v1.56.0
+
+require (
+	github.com/dustin/go-humanize v1.0.1 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/mattn/go-isatty v0.0.24 // indirect
+	github.com/ncruces/go-strftime v1.0.0 // indirect
+	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	golang.org/x/sys v0.47.0 // indirect
+	modernc.org/libc v1.74.4 // indirect
+	modernc.org/mathutil v1.7.1 // indirect
+	modernc.org/memory v1.11.0 // indirect
+)

go.sum

@@ -0,0 +1,50 @@
+github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
+github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
+github.com/google/pprof v0.0.0-20260802141513-ef3492d7dac3 h1:LMLX+LgTNWpfvCBdFebv6EsYotImrt/Ppc5cXIriCSo=
+github.com/google/pprof v0.0.0-20260802141513-ef3492d7dac3/go.mod h1:jl5iWTm0/hd5PjEYEOuwAJ57L/CibdZfrqZ5XA5GrCk=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/hashicorp/golang-lru/v2 v2.0.7 h1:a+bsQ5rvGLjzHuww6tVxozPZFVghXaHOwFs4luLUK2k=
+github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
+github.com/mattn/go-isatty v0.0.24 h1:tGZZoVgT/KiqK1c8ocVLeDS8BSWMRd47J3Lbz7vsReI=
+github.com/mattn/go-isatty v0.0.24/go.mod h1:nMCL3Zebbrt45jsMDgnfIwz6ydEQApk5oEI3HqDio6A=
+github.com/ncruces/go-strftime v1.0.0 h1:HMFp8mLCTPp341M/ZnA4qaf7ZlsbTc+miZjCLOFAw7w=
+github.com/ncruces/go-strftime v1.0.0/go.mod h1:Fwc5htZGVVkseilnfgOVb9mKy6w1naJmn9CehxcKcls=
+github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec h1:W09IVJc94icq4NjY3clb7Lk8O1qJ8BdBEF8z0ibU0rE=
+github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec/go.mod h1:qqbHyh8v60DhA7CoWK5oRCqLrMHRGoxYCSS9EjAz6Eo=
+golang.org/x/mod v0.37.0 h1:vF1DjpVEshcIqoEaauuHebaLk1O1forxjxBaVn884JQ=
+golang.org/x/mod v0.37.0/go.mod h1:m8S8VeM9r4dzDwjrKO0a1sZP3YjeMamRRlD+fmR2Q/0=
+golang.org/x/sync v0.21.0 h1:HLII4xRRTtCRkxYp4HNFF0Js/Og6q2i++KXbg0gHCwM=
+golang.org/x/sync v0.21.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
+golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
+golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+golang.org/x/tools v0.47.0 h1:7Kn5x/d1svx/PzryTsqeoZN4TZwqeH5pGWjefhLi/1Q=
+golang.org/x/tools v0.47.0/go.mod h1:dFHnyTvFWY212G+h7ZY4Vsp/K3U4/7W9TyVaAul8uCA=
+modernc.org/cc/v4 v4.29.1 h1:MKgdCV3WykTSPqpVrnxdEDS0HEd2FHpKZDzxzU5LyeI=
+modernc.org/cc/v4 v4.29.1/go.mod h1:OnovgIhbbMXMu1aISnJ0wvVD1KnW+cAUJkIrAWh+kVI=
+modernc.org/ccgo/v4 v4.34.6 h1:sBgfIwyN0TQ9C5hwIeuqyeAKyMWnbvj2fvpF4L11uzU=
+modernc.org/ccgo/v4 v4.34.6/go.mod h1:SZ8YcN9NG7XVsQYdm6jYBvi8PQP1qi+kqB6OhjqI3Fk=
+modernc.org/fileutil v1.4.0 h1:j6ZzNTftVS054gi281TyLjHPp6CPHr2KCxEXjEbD6SM=
+modernc.org/fileutil v1.4.0/go.mod h1:EqdKFDxiByqxLk8ozOxObDSfcVOv/54xDs/DUHdvCUU=
+modernc.org/gc/v2 v2.6.5 h1:nyqdV8q46KvTpZlsw66kWqwXRHdjIlJOhG6kxiV/9xI=
+modernc.org/gc/v2 v2.6.5/go.mod h1:YgIahr1ypgfe7chRuJi2gD7DBQiKSLMPgBQe9oIiito=
+modernc.org/gc/v3 v3.1.4 h1:2g65LGVSmFQrXeITAw97x7hCRvZFcyE1uDP+7Vng7JI=
+modernc.org/gc/v3 v3.1.4/go.mod h1:HFK/6AGESC7Ex+EZJhJ2Gni6cTaYpSMmU/cT9RmlfYY=
+modernc.org/goabi0 v0.2.0 h1:HvEowk7LxcPd0eq6mVOAEMai46V+i7Jrj13t4AzuNks=
+modernc.org/goabi0 v0.2.0/go.mod h1:CEFRnnJhKvWT1c1JTI3Avm+tgOWbkOu5oPA8eH8LnMI=
+modernc.org/libc v1.74.4 h1:fX1Omw4o2/1C2iRkkIsrQTasJQldLhRmuPreXLoWs9k=
+modernc.org/libc v1.74.4/go.mod h1:eeQAS9W3sZeKYMFubydxJpII9ybHWshk+7or7bLG9co=
+modernc.org/mathutil v1.7.1 h1:GCZVGXdaN8gTqB1Mf/usp1Y/hSqgI2vAGGP4jZMCxOU=
+modernc.org/mathutil v1.7.1/go.mod h1:4p5IwJITfppl0G4sUEDtCr4DthTaT47/N3aT6MhfgJg=
+modernc.org/memory v1.11.0 h1:o4QC8aMQzmcwCK3t3Ux/ZHmwFPzE6hf2Y5LbkRs+hbI=
+modernc.org/memory v1.11.0/go.mod h1:/JP4VbVC+K5sU2wZi9bHoq2MAkCnrt2r98UGeSK7Mjw=
+modernc.org/opt v0.2.0 h1:tGyef5ApycA7FSEOMraay9SaTk5zmbx7Tu+cJs4QKZg=
+modernc.org/opt v0.2.0/go.mod h1:03fq9lsNfvkYSfxrfUhZCWPk1lm4cq4N+Bh//bEtgns=
+modernc.org/sortutil v1.2.1 h1:+xyoGf15mM3NMlPDnFqrteY07klSFxLElE2PVuWIJ7w=
+modernc.org/sortutil v1.2.1/go.mod h1:7ZI3a3REbai7gzCLcotuw9AC4VZVpYMjDzETGsSMqJE=
+modernc.org/sqlite v1.56.0 h1:/D8e2RfFqoy/Zc6PuC76U28zFwmI/sYx1Kjm4yEn9e0=
+modernc.org/sqlite v1.56.0/go.mod h1:yCJ2cmAaIkHQ25oXWrF8H4O1lIfPYPR26yCEDj2P3pQ=
+modernc.org/strutil v1.2.1 h1:UneZBkQA+DX2Rp35KcM69cSsNES9ly8mQWD71HKlOA0=
+modernc.org/strutil v1.2.1/go.mod h1:EHkiggD70koQxjVdSBM3JKM7k6L0FbGE5eymy9i3B9A=
+modernc.org/token v1.1.0 h1:Xl7Ap9dKaEs5kLoOQeQmPWevfnk/DM5qcLcYlA8ys6Y=
+modernc.org/token v1.1.0/go.mod h1:UGzOrNV1mAFSEB63lOFHIpNRUVMvYTc6yu1SMY/XTDM=

internal/catalog/catalog.go

@@ -1,7 +1,11 @@
 // Package catalog holds table schemas and resolves table/column references.
 package catalog
 
-import "github.com/aybavs/sql-query-engine/internal/value"
+import (
+	"sort"
+
+	"github.com/aybavs/sql-query-engine/internal/value"
+)
 
 type Column struct {
 	Name string
@@ -35,3 +39,19 @@ func (c *Catalog) Table(name string) (*Table, bool) {
 	t, ok := c.tables[name]
 	return t, ok
 }
+
+// Tables returns every registered table, ordered by name so callers that
+// iterate the catalog behave deterministically.
+func (c *Catalog) Tables() []*Table {
+	names := make([]string, 0, len(c.tables))
+	for n := range c.tables {
+		names = append(names, n)
+	}
+	sort.Strings(names)
+
+	out := make([]*Table, 0, len(names))
+	for _, n := range names {
+		out = append(out, c.tables[n])
+	}
+	return out
+}

internal/catalog/catalog_test.go

@@ -31,3 +31,13 @@ func TestCatalogLookup(t *testing.T) {
 		t.Fatal("unknown column should not resolve")
 	}
 }
+
+func TestTablesIsSortedAndComplete(t *testing.T) {
+	c := New()
+	c.Add(&Table{Name: "users"})
+	c.Add(&Table{Name: "orders"})
+	got := c.Tables()
+	if len(got) != 2 || got[0].Name != "orders" || got[1].Name != "users" {
+		t.Fatalf("Tables() = %v, want [orders users]", got)
+	}
+}

internal/difftest/oracle.go

@@ -0,0 +1,128 @@
+// Package difftest compares this engine against SQLite on generated queries.
+// It is test-only: nothing outside its own tests imports it, so the SQLite
+// driver never enters the engine's build.
+package difftest
+
+import (
+	"database/sql"
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"github.com/aybavs/sql-query-engine/internal/catalog"
+	"github.com/aybavs/sql-query-engine/internal/csv"
+	"github.com/aybavs/sql-query-engine/internal/value"
+
+	_ "modernc.org/sqlite"
+)
+
+// Row is one result row of driver values (int64, float64, string, or nil).
+type Row []any
+
+// Oracle is an in-memory SQLite database loaded with the same fixture data as
+// the engine under test, used as the source of truth for query results.
+type Oracle struct{ db *sql.DB }
+
+func NewOracle(cat *catalog.Catalog, dataDir string) (*Oracle, error) {
+	db, err := sql.Open("sqlite", ":memory:")
+	if err != nil {
+		return nil, err
+	}
+	o := &Oracle{db: db}
+	for _, t := range cat.Tables() {
+		if err := o.load(t, dataDir); err != nil {
+			db.Close()
+			return nil, err
+		}
+	}
+	return o, nil
+}
+
+func (o *Oracle) load(t *catalog.Table, dataDir string) error {
+	cols := make([]string, len(t.Columns))
+	for i, c := range t.Columns {
+		cols[i] = c.Name + " " + sqliteType(c.Type)
+	}
+	create := fmt.Sprintf("CREATE TABLE %s (%s)", t.Name, strings.Join(cols, ", "))
+	if _, err := o.db.Exec(create); err != nil {
+		return fmt.Errorf("create %s: %w", t.Name, err)
+	}
+
+	rows, err := csv.Read(filepath.Join(dataDir, t.File), t.Columns)
+	if err != nil {
+		return err
+	}
+	placeholders := strings.TrimSuffix(strings.Repeat("?,", len(t.Columns)), ",")
+	insert := fmt.Sprintf("INSERT INTO %s VALUES (%s)", t.Name, placeholders)
+	for _, r := range rows {
+		args := make([]any, len(r))
+		for i, v := range r {
+			args[i] = driverValue(v)
+		}
+		if _, err := o.db.Exec(insert, args...); err != nil {
+			return fmt.Errorf("insert into %s: %w", t.Name, err)
+		}
+	}
+	return nil
+}
+
+// driverValue converts an engine value into what the SQLite driver expects,
+// preserving NULL rather than substituting a zero value.
+func driverValue(v value.Value) any {
+	if v.IsNull() {
+		return nil
+	}
+	switch v.Type {
+	case value.TInt:
+		return v.I
+	case value.TFloat:
+		return v.F
+	case value.TBool:
+		return v.B
+	default:
+		return v.S
+	}
+}
+
+func sqliteType(t value.Type) string {
+	switch t {
+	case value.TInt:
+		return "INTEGER"
+	case value.TFloat:
+		return "REAL"
+	case value.TBool:
+		return "INTEGER"
+	default:
+		return "TEXT"
+	}
+}
+
+// Query runs a statement and returns its rows as driver values.
+func (o *Oracle) Query(query string) ([]Row, error) {
+	rs, err := o.db.Query(query)
+	if err != nil {
+		return nil, err
+	}
+	defer rs.Close()
+
+	cols, err := rs.Columns()
+	if err != nil {
+		return nil, err
+	}
+
+	var out []Row
+	for rs.Next() {
+		cells := make([]any, len(cols))
+		ptrs := make([]any, len(cols))
+		for i := range cells {
+			ptrs[i] = &cells[i]
+		}
+		if err := rs.Scan(ptrs...); err != nil {
+			return nil, err
+		}
+		out = append(out, Row(cells))
+	}
+	return out, rs.Err()
+}
+
+func (o *Oracle) Close() error { return o.db.Close() }

internal/difftest/oracle_test.go

@@ -0,0 +1,73 @@
+package difftest
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/aybavs/sql-query-engine/internal/catalog"
+	"github.com/aybavs/sql-query-engine/internal/value"
+)
+
+func fixture(t *testing.T) (*catalog.Catalog, string) {
+	t.Helper()
+	dir := t.TempDir()
+	os.WriteFile(filepath.Join(dir, "users.csv"), []byte("1,alice,30\n2,bob,\n"), 0o644)
+	cat := catalog.New()
+	cat.Add(&catalog.Table{Name: "users", File: "users.csv", Columns: []catalog.Column{
+		{Name: "id", Type: value.TInt},
+		{Name: "name", Type: value.TText},
+		{Name: "age", Type: value.TInt},
+	}})
+	return cat, dir
+}
+
+func TestOracleLoadsAndQueries(t *testing.T) {
+	cat, dir := fixture(t)
+	o, err := NewOracle(cat, dir)
+	if err != nil {
+		t.Fatalf("NewOracle: %v", err)
+	}
+	defer o.Close()
+
+	rows, err := o.Query("SELECT name FROM users ORDER BY name")
+	if err != nil {
+		t.Fatalf("Query: %v", err)
+	}
+	if len(rows) != 2 {
+		t.Fatalf("rows = %v, want 2", rows)
+	}
+	if s, ok := rows[0][0].(string); !ok || s != "alice" {
+		t.Fatalf("first row = %v, want alice", rows[0])
+	}
+}
+
+func TestOracleKeepsEmptyFieldsNull(t *testing.T) {
+	cat, dir := fixture(t)
+	o, err := NewOracle(cat, dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer o.Close()
+
+	rows, err := o.Query("SELECT age FROM users WHERE name = 'bob'")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(rows) != 1 || rows[0][0] != nil {
+		t.Fatalf("bob's age = %v, want NULL", rows)
+	}
+}
+
+func TestOracleReportsInvalidQuery(t *testing.T) {
+	cat, dir := fixture(t)
+	o, err := NewOracle(cat, dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer o.Close()
+
+	if _, err := o.Query("SELECT nope FROM users"); err == nil {
+		t.Fatal("expected an error for an unknown column")
+	}
+}