Add more godocs and tests

dbutil/massinsert.go

@@ -23,6 +23,7 @@ type MassInsertable[T Array] interface {
 	GetMassInsertValues() T
 }
 
+// MassInsertBuilder contains pre-validated templates for building mass insert SQL queries.
 type MassInsertBuilder[Item MassInsertable[DynamicParams], StaticParams Array, DynamicParams Array] struct {
 	queryTemplate       string
 	placeholderTemplate string
@@ -114,6 +115,31 @@ func NewMassInsertBuilder[Item MassInsertable[DynamicParams], StaticParams Array
 	}
 }
 
+// Build constructs a ready-to-use mass insert SQL query using the prepared templates in this builder.
+//
+// This method always only produces one query. If there are lots of items,
+// chunking them beforehand may be required to avoid query parameter limits.
+// For example, SQLite (3.32+) has a limit of 32766 parameters by default,
+// while Postgres allows up to 65535. To find out if there are too many items,
+// divide the maximum number of parameters by the number of dynamic columns in
+// your data and subtract the number of static columns.
+//
+// Example of chunking input data:
+//
+//	var mib dbutil.MassInsertBuilder
+//	var db *dbutil.Database
+//	func MassInsert(ctx context.Context, ..., data []T) error {
+//		return db.DoTxn(ctx, nil, func(ctx context.Context) error {
+//			for _, chunk := range exslices.Chunk(data, 100) {
+//				query, params := mib.Build(staticParams)
+//				_, err := db.Exec(ctx, query, params...)
+//				if err != nil {
+//					return err
+//				}
+//			}
+//			return nil
+//		}
+//	}
 func (mib *MassInsertBuilder[Item, StaticParams, DynamicParams]) Build(static StaticParams, data []Item) (query string, params []any) {
 	var itemValues DynamicParams
 	params = make([]any, len(static)+len(itemValues)*len(data))

dbutil/massinsert_test.go

@@ -7,11 +7,16 @@
 package dbutil_test
 
 import (
+	"fmt"
+	"math/rand"
+	"strings"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 
 	"go.mau.fi/util/dbutil"
+	"go.mau.fi/util/random"
 )
 
 type AbstractMassInsertable[T dbutil.Array] struct {
@@ -45,3 +50,83 @@ func TestMassInsertBuilder_Build(t *testing.T) {
 	assert.Equal(t, "INSERT INTO foo VALUES ($1, $2), ($1, $3), ($1, $4)", query)
 	assert.Equal(t, []any{"hi", "hmm", "meow", "third"}, values)
 }
+
+func TestMassInsertBuilder_Build_MultiValue(t *testing.T) {
+	ts := time.Now().UnixMilli()
+	builder := dbutil.NewMassInsertBuilder[AbstractMassInsertable[[5]any], [3]any]("INSERT INTO foo VALUES ($1, $2, $3, $4, $5, $6, $7, $8)", "($1, $2, $%d, $%d, $3, $%d, $%d, $%d)")
+	query, values := builder.Build([3]any{"first", "second", 3}, []AbstractMassInsertable[[5]any]{
+		{[5]any{"foo1", 123, true, "meow", ts}},
+		{[5]any{"foo2", 666, false, "meow", ts + 1}},
+		{[5]any{"foo3", 999, true, "no meow", ts + 2}},
+		{[5]any{"foo4", 0, true, "meow!", 0}},
+	})
+	assert.Equal(t, "INSERT INTO foo VALUES ($1, $2, $4, $5, $3, $6, $7, $8), ($1, $2, $9, $10, $3, $11, $12, $13), ($1, $2, $14, $15, $3, $16, $17, $18), ($1, $2, $19, $20, $3, $21, $22, $23)", query)
+	assert.Equal(t, []any{"first", "second", 3, "foo1", 123, true, "meow", ts, "foo2", 666, false, "meow", ts + 1, "foo3", 999, true, "no meow", ts + 2, "foo4", 0, true, "meow!", 0}, values)
+}
+
+func TestMassInsertBuilder_Build_CompareWithManual(t *testing.T) {
+	builder := dbutil.NewMassInsertBuilder[AbstractMassInsertable[[5]any], [3]any]("INSERT INTO foo VALUES ($1, $2, $3, $4, $5, $6, $7, $8)", "($1, $2, $%d, $%d, $3, $%d, $%d, $%d)")
+	data := makeBenchmarkData[[5]any](100)
+	manualQuery, manualParams := buildMassInsertManual(data)
+	query, params := builder.Build([3]any{"first", "second", 3}, data)
+	assert.Equal(t, manualQuery, query)
+	assert.Equal(t, manualParams, params)
+}
+
+func makeBenchmarkData[T dbutil.Array](n int) []AbstractMassInsertable[T] {
+	outArr := make([]AbstractMassInsertable[T], n)
+	dataLen := len(outArr[0].Data)
+	for i := 0; i < dataLen; i++ {
+		var val any
+		switch rand.Intn(4) {
+		case 0:
+			val = rand.Intn(1000)
+		case 1:
+			val = rand.Intn(1) == 0
+		case 2:
+			val = time.Now().UnixMilli()
+		case 3:
+			val = random.String(16)
+		}
+		for j := 0; j < len(outArr); j++ {
+			outArr[j].Data[i] = val
+		}
+	}
+	return outArr
+}
+
+func BenchmarkMassInsertBuilder_Build5x100(b *testing.B) {
+	builder := dbutil.NewMassInsertBuilder[AbstractMassInsertable[[5]any], [3]any]("INSERT INTO foo VALUES ($1, $2, $3, $4, $5, $6, $7, $8)", "($1, $2, $%d, $%d, $3, $%d, $%d, $%d)")
+	data := makeBenchmarkData[[5]any](100)
+	for i := 0; i < b.N; i++ {
+		builder.Build([3]any{"first", "second", 3}, data)
+	}
+}
+
+func buildMassInsertManual(data []AbstractMassInsertable[[5]any]) (string, []any) {
+	const queryTemplate = `INSERT INTO foo VALUES %s`
+	const placeholderTemplate = "($1, $2, $%d, $%d, $3, $%d, $%d, $%d)"
+	placeholders := make([]string, len(data))
+	params := make([]any, 3+len(data)*5)
+	params[0] = "first"
+	params[1] = "second"
+	params[2] = 3
+	for j, item := range data {
+		baseIndex := j*5 + 3
+		params[baseIndex] = item.Data[0]
+		params[baseIndex+1] = item.Data[1]
+		params[baseIndex+2] = item.Data[2]
+		params[baseIndex+3] = item.Data[3]
+		params[baseIndex+4] = item.Data[4]
+		placeholders[j] = fmt.Sprintf(placeholderTemplate, baseIndex+1, baseIndex+2, baseIndex+3, baseIndex+4, baseIndex+5)
+	}
+	query := fmt.Sprintf(queryTemplate, strings.Join(placeholders, ", "))
+	return query, params
+}
+
+func BenchmarkMassInsertBuilder_Build5x100_Manual(b *testing.B) {
+	data := makeBenchmarkData[[5]any](100)
+	for i := 0; i < b.N; i++ {
+		buildMassInsertManual(data)
+	}
+}