diff --git a/driver/conn.go b/driver/conn.go
index 99da5ae..a2564a3 100644
--- a/driver/conn.go
+++ b/driver/conn.go
@@ -104,6 +104,7 @@ func (c *Conn) Begin() (driver.Tx, error) {
 		return nil, err
 	}
 	c.tx = tx
+	log.Debug("%p BEGIN", c.tx)
 	return c, nil
 }
 
@@ -120,6 +121,7 @@ func (c *Conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, e
 		return nil, err
 	}
 	c.tx = tx
+	log.Debug("%p BEGIN", c.tx)
 	return c, nil
 }
 
@@ -127,6 +129,7 @@ func (c *Conn) Rollback() error {
 	if c.tx == nil {
 		return nil
 	}
+	log.Debug("%p ROLLBACK", c.tx)
 	err := c.tx.Rollback()
 	c.tx = nil
 	return err
@@ -136,6 +139,7 @@ func (c *Conn) Commit() error {
 	if c.tx == nil {
 		return nil
 	}
+	log.Debug("%p COMMIT", c.tx)
 	err := c.tx.Commit()
 	c.tx = nil
 	return err
@@ -148,7 +152,7 @@ func (c *Conn) QueryContext(ctx context.Context, query string, args []driver.Nam
 	var err error
 	autocommit := false
 
-	log.Info("Conn.QueryContext: %s", query)
+	log.Debug("Conn.QueryContext: %s", query)
 
 	tx := c.tx
 
diff --git a/engine/agnostic/index.go b/engine/agnostic/index.go
index 8a2bb94..06cc363 100644
--- a/engine/agnostic/index.go
+++ b/engine/agnostic/index.go
@@ -20,6 +20,7 @@ type Index interface {
 	Remove(*list.Element)
 	Name() string
 	CanSourceWith(p Predicate) (bool, int64)
+	Get(values []any) (*list.Element, error)
 }
 
 type HashIndex struct {
diff --git a/engine/agnostic/relation.go b/engine/agnostic/relation.go
index 3703214..d10e358 100644
--- a/engine/agnostic/relation.go
+++ b/engine/agnostic/relation.go
@@ -56,6 +56,35 @@ func NewRelation(schema, name string, attributes []Attribute, pk []string) (*Rel
 	return r, nil
 }
 
+func (r *Relation) CheckPrimaryKey(tuple *Tuple) (bool, error) {
+
+	var index Index
+	for i, _ := range r.indexes {
+		if strings.HasPrefix(r.indexes[i].Name(), "pk") {
+			index = r.indexes[i]
+			break
+		}
+	}
+	if index == nil {
+		return false, fmt.Errorf("primary key index not found")
+	}
+
+	var vals []any
+	for _, idx := range r.pk {
+		vals = append(vals, tuple.values[idx])
+	}
+
+	e, err := index.Get(vals)
+	if err != nil {
+		return false, err
+	}
+	if e == nil {
+		return true, nil
+	}
+
+	return false, nil
+}
+
 func (r *Relation) Attribute(name string) (int, Attribute, error) {
 	name = strings.ToLower(name)
 	index, ok := r.attrIndex[name]
diff --git a/engine/agnostic/transaction.go b/engine/agnostic/transaction.go
index b1d6bc3..7d1275a 100644
--- a/engine/agnostic/transaction.go
+++ b/engine/agnostic/transaction.go
@@ -446,8 +446,14 @@ func (t *Transaction) Insert(schema, relation string, values map[string]any) (*T
 		return nil, t.abort(fmt.Errorf("attribute %s does not exist in relation %s", k, relation))
 	}
 
-	// check primary key
-	// TODO
+	// check primary key violation
+	ok, err := r.CheckPrimaryKey(tuple)
+	if err != nil {
+		return nil, t.abort(err)
+	}
+	if !ok {
+		return nil, t.abort(fmt.Errorf("primary key violation"))
+	}
 
 	// insert into row list
 	log.Debug("Inserting %v", tuple.values)
diff --git a/engine/executor/tx.go b/engine/executor/tx.go
index ce620a3..2ede54f 100644
--- a/engine/executor/tx.go
+++ b/engine/executor/tx.go
@@ -57,12 +57,10 @@ func NewTx(ctx context.Context, e *Engine, opts sql.TxOptions) (*Tx, error) {
 		parser.GrantToken:    grantExecutor,
 	}
 
-	log.Info("Begin(%p)", t.tx)
 	return t, nil
 }
 
 func (t *Tx) QueryContext(ctx context.Context, query string, args []NamedValue) ([]string, []*agnostic.Tuple, error) {
-	log.Info("QueryContext(%p, %s)", t.tx, query)
 
 	instructions, err := parser.ParseInstruction(query)
 	if err != nil {
@@ -91,14 +89,12 @@ func (t *Tx) QueryContext(ctx context.Context, query string, args []NamedValue)
 
 // Commit the transaction on server
 func (t *Tx) Commit() error {
-	log.Info("Commit(%p)", t.tx)
 	_, err := t.tx.Commit()
 	return err
 }
 
 // Rollback all changes
 func (t *Tx) Rollback() error {
-	log.Info("Rollback(%p)", t.tx)
 	t.tx.Rollback()
 	return nil
 }