initialisationComplete flag synchronized closes #4803 (rebased) (#4886)

* Add test for #4803: Race condition in initialisationComplete flag

Add TestInitialisationComplete_RaceCondition to demonstrate the data race
that occurs when the initialisationComplete boolean flag is accessed
concurrently by multiple goroutines without synchronization.

The test simulates:
- Init goroutine writing to the flag
- Query executor reading via isInitialised()
- Notification handler reading the flag directly

This test will fail when run with the -race flag, exposing the bug.

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix #4803: Use atomic.Bool for initialisationComplete flag

Replace the plain boolean initialisationComplete field with atomic.Bool
to prevent data races when accessed concurrently by multiple goroutines.

Changes:
- Change field type from bool to atomic.Bool
- Use .Store(true) for writes
- Use .Load() for reads in isInitialised() and handleConnectionUpdateNotification()
- Update test to use atomic operations

The test now passes with -race flag, confirming the race condition is fixed.

---------

Co-authored-by: Claude <noreply@anthropic.com>

pkg/interactive/interactive_client.go

@@ -10,6 +10,7 @@ import (
 	"os/signal"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/alecthomas/chroma/formatters"
@@ -58,7 +59,7 @@ type InteractiveClient struct {
 	// channel used internally to pass the initialisation result
 	initResultChan chan *db_common.InitResult
 	// flag set when initialisation is complete (with or without errors)
-	initialisationComplete bool
+	initialisationComplete atomic.Bool
 	afterClose             AfterPromptCloseAction
 	// lock while execution is occurring to avoid errors/warnings being shown
 	executionLock sync.Mutex
@@ -731,7 +732,7 @@ func (c *InteractiveClient) handleConnectionUpdateNotification(ctx context.Conte
 	// ignore schema update notifications until initialisation is complete
 	// (we may receive schema update messages from the initial refresh connections, but we do not need to reload
 	// the schema as we will have already loaded the correct schema)
-	if !c.initialisationComplete {
+	if !c.initialisationComplete.Load() {
 		log.Printf("[INFO] received schema update notification but ignoring it as we are initializing")
 		return
 	}

pkg/interactive/interactive_client_init.go

@@ -16,7 +16,7 @@ import (
 func (c *InteractiveClient) handleInitResult(ctx context.Context, initResult *db_common.InitResult) {
 	// whatever happens, set initialisationComplete
 	defer func() {
-		c.initialisationComplete = true
+		c.initialisationComplete.Store(true)
 	}()
 
 	if initResult.Error != nil {
@@ -127,7 +127,7 @@ func (c *InteractiveClient) readInitDataStream(ctx context.Context) {
 // return whether the client is initialises
 // there are 3 conditions>
 func (c *InteractiveClient) isInitialised() bool {
-	return c.initialisationComplete
+	return c.initialisationComplete.Load()
 }
 
 func (c *InteractiveClient) waitForInitData(ctx context.Context) error {

pkg/interactive/interactive_client_test.go

@@ -2,6 +2,7 @@ package interactive
 
 import (
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/c-bata/go-prompt"
@@ -289,9 +290,8 @@ func TestIsInitialised(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			c := &InteractiveClient{
-				initialisationComplete: tt.initialisationComplete,
-			}
+			c := &InteractiveClient{}
+			c.initialisationComplete.Store(tt.initialisationComplete)
 
 			result := c.isInitialised()
 
@@ -532,3 +532,51 @@ func TestCancelActiveQueryIfAny(t *testing.T) {
 		}
 	})
 }
+
+// TestInitialisationComplete_RaceCondition tests that concurrent access to
+// the initialisationComplete flag does not cause data races.
+//
+// This test simulates the real-world scenario where:
+// - One goroutine (init goroutine) writes to initialisationComplete
+// - Other goroutines (query executor, notification handler) read from it
+//
+// Bug: #4803
+func TestInitialisationComplete_RaceCondition(t *testing.T) {
+	c := &InteractiveClient{}
+	c.initialisationComplete.Store(false)
+
+	var wg sync.WaitGroup
+
+	// Simulate initialization goroutine writing to the flag
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for i := 0; i < 100; i++ {
+			c.initialisationComplete.Store(true)
+			c.initialisationComplete.Store(false)
+		}
+	}()
+
+	// Simulate query executor reading the flag
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for i := 0; i < 100; i++ {
+			_ = c.isInitialised()
+		}
+	}()
+
+	// Simulate notification handler reading the flag
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for i := 0; i < 100; i++ {
+			// Check the flag directly (as handleConnectionUpdateNotification does)
+			if !c.initialisationComplete.Load() {
+				continue
+			}
+		}
+	}()
+
+	wg.Wait()
+}