Better handling of preloads

pkg/common/adapters/database/RELATION_LOADING.md

@@ -0,0 +1,218 @@
+# Automatic Relation Loading Strategies
+
+## Overview
+
+**NEW:** The database adapters now **automatically** choose the optimal loading strategy by inspecting your model's relationship tags!
+
+Simply use `PreloadRelation()` and the system automatically:
+- Detects relationship type from Bun/GORM tags
+- Uses **JOIN** for many-to-one and one-to-one (efficient, no duplication)
+- Uses **separate query** for one-to-many and many-to-many (avoids duplication)
+
+## How It Works
+
+```go
+// Just write this - the system handles the rest!
+db.NewSelect().
+    Model(&links).
+    PreloadRelation("Provider").  // ✓ Auto-detects belongs-to → uses JOIN
+    PreloadRelation("Tags").      // ✓ Auto-detects has-many → uses separate query
+    Scan(ctx, &links)
+```
+
+### Detection Logic
+
+The system inspects your model's struct tags:
+
+**Bun models:**
+```go
+type Link struct {
+    Provider   *Provider `bun:"rel:belongs-to"`   // → Detected: belongs-to → JOIN
+    Tags       []Tag     `bun:"rel:has-many"`     // → Detected: has-many → Separate query
+}
+```
+
+**GORM models:**
+```go
+type Link struct {
+    ProviderID int
+    Provider   *Provider `gorm:"foreignKey:ProviderID"`  // → Detected: belongs-to → JOIN
+    Tags       []Tag     `gorm:"many2many:link_tags"`    // → Detected: many-to-many → Separate query
+}
+```
+
+**Type inference (fallback):**
+- `[]Type` (slice) → has-many → Separate query
+- `*Type` (pointer) → belongs-to → JOIN
+- `Type` (struct) → belongs-to → JOIN
+
+### What Gets Logged
+
+Enable debug logging to see strategy selection:
+
+```go
+bunAdapter.EnableQueryDebug()
+```
+
+**Output:**
+```
+DEBUG: PreloadRelation 'Provider' detected as: belongs-to
+INFO:  Using JOIN strategy for belongs-to relation 'Provider'
+DEBUG: PreloadRelation 'Links' detected as: has-many
+DEBUG: Using separate query for has-many relation 'Links'
+```
+
+## Relationship Types
+
+| Bun Tag | GORM Pattern | Field Type | Strategy | Why |
+|---------|--------------|------------|----------|-----|
+| `rel:has-many` | Slice field | `[]Type` | Separate Query | Avoids duplicating parent data |
+| `rel:belongs-to` | `foreignKey:` | `*Type` | JOIN | Single parent, no duplication |
+| `rel:has-one` | Single pointer | `*Type` | JOIN | One-to-one, no duplication |
+| `rel:many-to-many` | `many2many:` | `[]Type` | Separate Query | Complex join, avoid cartesian |
+
+## Manual Override
+
+If you need to force a specific strategy, use `JoinRelation()`:
+
+```go
+// Force JOIN even for has-many (not recommended)
+db.NewSelect().
+    Model(&providers).
+    JoinRelation("Links").  // Explicitly use JOIN
+    Scan(ctx, &providers)
+```
+
+## Examples
+
+### Automatic Strategy Selection (Recommended)
+
+```go
+// Example 1: Loading parent provider for each link
+// System detects belongs-to → uses JOIN automatically
+db.NewSelect().
+    Model(&links).
+    PreloadRelation("Provider", func(q common.SelectQuery) common.SelectQuery {
+        return q.Where("active = ?", true)
+    }).
+    Scan(ctx, &links)
+
+// Generated SQL: Single query with JOIN
+// SELECT links.*, providers.*
+// FROM links
+// LEFT JOIN providers ON links.provider_id = providers.id
+// WHERE providers.active = true
+
+// Example 2: Loading child links for each provider
+// System detects has-many → uses separate query automatically
+db.NewSelect().
+    Model(&providers).
+    PreloadRelation("Links", func(q common.SelectQuery) common.SelectQuery {
+        return q.Where("active = ?", true)
+    }).
+    Scan(ctx, &providers)
+
+// Generated SQL: Two queries
+// Query 1: SELECT * FROM providers
+// Query 2: SELECT * FROM links
+//          WHERE provider_id IN (1, 2, 3, ...)
+//          AND active = true
+```
+
+### Mixed Relationships
+
+```go
+type Order struct {
+    ID         int
+    CustomerID int
+    Customer   *Customer `bun:"rel:belongs-to"`    // JOIN
+    Items      []Item    `bun:"rel:has-many"`      // Separate
+    Invoice    *Invoice  `bun:"rel:has-one"`       // JOIN
+}
+
+// All three handled optimally!
+db.NewSelect().
+    Model(&orders).
+    PreloadRelation("Customer").  // → JOIN (many-to-one)
+    PreloadRelation("Items").     // → Separate (one-to-many)
+    PreloadRelation("Invoice").   // → JOIN (one-to-one)
+    Scan(ctx, &orders)
+```
+
+## Performance Benefits
+
+### Before (Manual Strategy Selection)
+
+```go
+// You had to remember which to use:
+.PreloadRelation("Provider")  // Should I use PreloadRelation or JoinRelation?
+.PreloadRelation("Links")     // Which is more efficient here?
+```
+
+### After (Automatic Selection)
+
+```go
+// Just use PreloadRelation everywhere:
+.PreloadRelation("Provider")  // ✓ System uses JOIN automatically
+.PreloadRelation("Links")     // ✓ System uses separate query automatically
+```
+
+## Migration Guide
+
+**No changes needed!** If you're already using `PreloadRelation()`, it now automatically optimizes:
+
+```go
+// Before: Always used separate query
+.PreloadRelation("Provider")  // Inefficient: extra round trip
+
+// After: Automatic optimization
+.PreloadRelation("Provider")  // ✓ Now uses JOIN automatically!
+```
+
+## Implementation Details
+
+### Supported Bun Tags
+- `rel:has-many` → Separate query
+- `rel:belongs-to` → JOIN
+- `rel:has-one` → JOIN
+- `rel:many-to-many` or `rel:m2m` → Separate query
+
+### Supported GORM Patterns
+- `many2many:` tag → Separate query
+- `foreignKey:` tag → JOIN (belongs-to)
+- `[]Type` slice without many2many → Separate query (has-many)
+- `*Type` pointer with foreignKey → JOIN (belongs-to)
+- `*Type` pointer without foreignKey → JOIN (has-one)
+
+### Fallback Behavior
+- `[]Type` (slice) → Separate query (safe default for collections)
+- `*Type` or `Type` (single) → JOIN (safe default for single relations)
+- Unknown → Separate query (safest default)
+
+## Debugging
+
+To see strategy selection in action:
+
+```go
+// Enable debug logging
+bunAdapter.EnableQueryDebug()  // or gormAdapter.EnableQueryDebug()
+
+// Run your query
+db.NewSelect().
+    Model(&records).
+    PreloadRelation("RelationName").
+    Scan(ctx, &records)
+
+// Check logs for:
+// - "PreloadRelation 'X' detected as: belongs-to"
+// - "Using JOIN strategy for belongs-to relation 'X'"
+// - Actual SQL queries executed
+```
+
+## Best Practices
+
+1. **Use PreloadRelation() for everything** - Let the system optimize
+2. **Define proper relationship tags** - Ensures correct detection
+3. **Only use JoinRelation() for overrides** - When you know better than auto-detection
+4. **Enable debug logging during development** - Verify optimal strategies are chosen
+5. **Trust the system** - It's designed to choose correctly based on relationship type

pkg/common/adapters/database/alias_test.go

@@ -0,0 +1,67 @@
+package database
+
+import (
+	"testing"
+)
+
+func TestNormalizeTableAlias(t *testing.T) {
+	tests := []struct {
+		name          string
+		query         string
+		expectedAlias string
+		tableName     string
+		want          string
+	}{
+		{
+			name:          "strips incorrect alias from simple condition",
+			query:         "APIL.rid_hub = 2576",
+			expectedAlias: "apiproviderlink",
+			tableName:     "apiproviderlink",
+			want:          "rid_hub = 2576",
+		},
+		{
+			name:          "keeps correct alias",
+			query:         "apiproviderlink.rid_hub = 2576",
+			expectedAlias: "apiproviderlink",
+			tableName:     "apiproviderlink",
+			want:          "apiproviderlink.rid_hub = 2576",
+		},
+		{
+			name:          "strips incorrect alias with multiple conditions",
+			query:         "APIL.rid_hub = ? AND APIL.active = ?",
+			expectedAlias: "apiproviderlink",
+			tableName:     "apiproviderlink",
+			want:          "rid_hub = ? AND active = ?",
+		},
+		{
+			name:          "handles mixed correct and incorrect aliases",
+			query:         "APIL.rid_hub = ? AND apiproviderlink.active = ?",
+			expectedAlias: "apiproviderlink",
+			tableName:     "apiproviderlink",
+			want:          "rid_hub = ? AND apiproviderlink.active = ?",
+		},
+		{
+			name:          "handles parentheses",
+			query:         "(APIL.rid_hub = ?)",
+			expectedAlias: "apiproviderlink",
+			tableName:     "apiproviderlink",
+			want:          "(rid_hub = ?)",
+		},
+		{
+			name:          "no alias in query",
+			query:         "rid_hub = ?",
+			expectedAlias: "apiproviderlink",
+			tableName:     "apiproviderlink",
+			want:          "rid_hub = ?",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := normalizeTableAlias(tt.query, tt.expectedAlias, tt.tableName)
+			if got != tt.want {
+				t.Errorf("normalizeTableAlias() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}

pkg/common/adapters/database/bun.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"reflect"
 	"strings"
+	"time"
 
 	"github.com/uptrace/bun"
 
@@ -15,6 +16,24 @@ import (
 	"github.com/bitechdev/ResolveSpec/pkg/reflection"
 )
 
+// QueryDebugHook is a Bun query hook that logs all SQL queries including preloads
+type QueryDebugHook struct{}
+
+func (h *QueryDebugHook) BeforeQuery(ctx context.Context, event *bun.QueryEvent) context.Context {
+	return ctx
+}
+
+func (h *QueryDebugHook) AfterQuery(ctx context.Context, event *bun.QueryEvent) {
+	query := event.Query
+	duration := time.Since(event.StartTime)
+
+	if event.Err != nil {
+		logger.Error("SQL Query Failed [%s]: %s. Error: %v", duration, query, event.Err)
+	} else {
+		logger.Debug("SQL Query Success [%s]: %s", duration, query)
+	}
+}
+
 // BunAdapter adapts Bun to work with our Database interface
 // This demonstrates how the abstraction works with different ORMs
 type BunAdapter struct {
@@ -26,6 +45,20 @@ func NewBunAdapter(db *bun.DB) *BunAdapter {
 	return &BunAdapter{db: db}
 }
 
+// EnableQueryDebug enables query debugging which logs all SQL queries including preloads
+// This is useful for debugging preload queries that may be failing
+func (b *BunAdapter) EnableQueryDebug() {
+	b.db.AddQueryHook(&QueryDebugHook{})
+	logger.Info("Bun query debug mode enabled - all SQL queries will be logged")
+}
+
+// DisableQueryDebug removes all query hooks
+func (b *BunAdapter) DisableQueryDebug() {
+	// Create a new DB without hooks
+	// Note: Bun doesn't have a RemoveQueryHook, so we'd need to track hooks manually
+	logger.Info("To disable query debug, recreate the BunAdapter without adding the hook")
+}
+
 func (b *BunAdapter) NewSelect() common.SelectQuery {
 	return &BunSelectQuery{
 		query: b.db.NewSelect(),
@@ -107,6 +140,8 @@ type BunSelectQuery struct {
 	tableName        string  // Just the table name, without schema
 	tableAlias       string
 	deferredPreloads []deferredPreload // Preloads to execute as separate queries
+	inJoinContext    bool              // Track if we're in a JOIN relation context
+	joinTableAlias   string            // Alias to use for JOIN conditions
 }
 
 // deferredPreload represents a preload that will be executed as a separate query
@@ -156,10 +191,106 @@ func (b *BunSelectQuery) ColumnExpr(query string, args ...interface{}) common.Se
 }
 
 func (b *BunSelectQuery) Where(query string, args ...interface{}) common.SelectQuery {
+	// If we're in a JOIN context, add table prefix to unqualified columns
+	if b.inJoinContext && b.joinTableAlias != "" {
+		query = addTablePrefix(query, b.joinTableAlias)
+	} else if b.tableAlias != "" && b.tableName != "" {
+		// If we have a table alias defined, check if the query references a different alias
+		// This can happen in preloads where the user expects a certain alias but Bun generates another
+		query = normalizeTableAlias(query, b.tableAlias, b.tableName)
+	}
 	b.query = b.query.Where(query, args...)
 	return b
 }
 
+// addTablePrefix adds a table prefix to unqualified column references
+// This is used in JOIN contexts where conditions must reference the joined table
+func addTablePrefix(query, tableAlias string) string {
+	if tableAlias == "" || query == "" {
+		return query
+	}
+
+	// Split on spaces and parentheses to find column references
+	parts := strings.FieldsFunc(query, func(r rune) bool {
+		return r == ' ' || r == '(' || r == ')' || r == ','
+	})
+
+	modified := query
+	for _, part := range parts {
+		// Check if this looks like an unqualified column reference
+		// (no dot, and likely a column name before an operator)
+		if !strings.Contains(part, ".") {
+			// Extract potential column name (before = or other operators)
+			for _, op := range []string{"=", "!=", "<>", ">", ">=", "<", "<=", " LIKE ", " IN ", " IS "} {
+				if strings.Contains(part, op) {
+					colName := strings.Split(part, op)[0]
+					colName = strings.TrimSpace(colName)
+					if colName != "" && !isOperatorOrKeyword(colName) {
+						// Add table prefix
+						prefixed := tableAlias + "." + colName + strings.TrimPrefix(part, colName)
+						modified = strings.ReplaceAll(modified, part, prefixed)
+						logger.Debug("Adding table prefix '%s' to column '%s' in JOIN condition", tableAlias, colName)
+					}
+					break
+				}
+			}
+		}
+	}
+
+	return modified
+}
+
+// isOperatorOrKeyword checks if a string is likely an operator or SQL keyword
+func isOperatorOrKeyword(s string) bool {
+	s = strings.ToUpper(strings.TrimSpace(s))
+	keywords := []string{"AND", "OR", "NOT", "IN", "IS", "NULL", "TRUE", "FALSE", "LIKE", "BETWEEN"}
+	for _, kw := range keywords {
+		if s == kw {
+			return true
+		}
+	}
+	return false
+}
+
+// normalizeTableAlias replaces table alias prefixes in SQL conditions
+// This handles cases where a user references a table alias that doesn't match
+// what Bun generates (common in preload contexts)
+func normalizeTableAlias(query, expectedAlias, tableName string) string {
+	// Pattern: <word>.<column> where <word> might be an incorrect alias
+	// We'll look for patterns like "APIL.column" and either:
+	// 1. Remove the alias prefix entirely (safest)
+	// 2. Replace with the expected alias
+
+	// For now, we'll use a simple approach: if the query contains a dot (qualified reference)
+	// and that prefix is not the expected alias or table name, strip it
+
+	// Split on spaces and parentheses to find qualified references
+	parts := strings.FieldsFunc(query, func(r rune) bool {
+		return r == ' ' || r == '(' || r == ')' || r == ','
+	})
+
+	modified := query
+	for _, part := range parts {
+		// Check if this looks like a qualified column reference
+		if dotIndex := strings.Index(part, "."); dotIndex > 0 {
+			prefix := part[:dotIndex]
+			column := part[dotIndex+1:]
+
+			// Check if the prefix matches our expected alias or table name (case-insensitive)
+			if !strings.EqualFold(prefix, expectedAlias) &&
+				!strings.EqualFold(prefix, tableName) &&
+				!strings.EqualFold(prefix, strings.ToLower(tableName)) {
+				// This is a different alias - remove the prefix
+				logger.Debug("Stripping incorrect alias '%s' from WHERE condition, keeping just '%s'", prefix, column)
+				// Replace the qualified reference with just the column name
+				modified = strings.ReplaceAll(modified, part, column)
+			}
+		}
+	}
+
+	return modified
+}
+
 func (b *BunSelectQuery) WhereOr(query string, args ...interface{}) common.SelectQuery {
 	b.query = b.query.WhereOr(query, args...)
 	return b
@@ -288,6 +419,27 @@ func (b *BunSelectQuery) Preload(relation string, conditions ...interface{}) com
 // }
 
 func (b *BunSelectQuery) PreloadRelation(relation string, apply ...func(common.SelectQuery) common.SelectQuery) common.SelectQuery {
+	// Auto-detect relationship type and choose optimal loading strategy
+	// Get the model from the query if available
+	model := b.query.GetModel()
+	if model != nil && model.Value() != nil {
+		relType := reflection.GetRelationType(model.Value(), relation)
+
+		// Log the detected relationship type
+		logger.Debug("PreloadRelation '%s' detected as: %s", relation, relType)
+
+		// If this is a belongs-to or has-one relation, use JOIN for better performance
+		if relType.ShouldUseJoin() {
+			logger.Info("Using JOIN strategy for %s relation '%s'", relType, relation)
+			return b.JoinRelation(relation, apply...)
+		}
+
+		// For has-many, many-to-many, or unknown: use separate query (safer default)
+		if relType == reflection.RelationHasMany || relType == reflection.RelationManyToMany {
+			logger.Debug("Using separate query for %s relation '%s'", relType, relation)
+		}
+	}
+
 	// Check if this relation chain would create problematic long aliases
 	relationParts := strings.Split(relation, ".")
 	aliasChain := strings.ToLower(strings.Join(relationParts, "__"))
@@ -350,6 +502,28 @@ func (b *BunSelectQuery) PreloadRelation(relation string, apply ...func(common.S
 			db:    b.db,
 		}
 
+		// Try to extract table name and alias from the preload model
+		if model := sq.GetModel(); model != nil && model.Value() != nil {
+			modelValue := model.Value()
+
+			// Extract table name if model implements TableNameProvider
+			if provider, ok := modelValue.(common.TableNameProvider); ok {
+				fullTableName := provider.TableName()
+				wrapper.schema, wrapper.tableName = parseTableName(fullTableName)
+			}
+
+			// Extract table alias if model implements TableAliasProvider
+			if provider, ok := modelValue.(common.TableAliasProvider); ok {
+				wrapper.tableAlias = provider.TableAlias()
+				// Apply the alias to the Bun query so conditions can reference it
+				if wrapper.tableAlias != "" {
+					// Note: Bun's Relation() already sets up the table, but we can add
+					// the alias explicitly if needed
+					logger.Debug("Preload relation '%s' using table alias: %s", relation, wrapper.tableAlias)
+				}
+			}
+		}
+
 		// Start with the interface value (not pointer)
 		current := common.SelectQuery(wrapper)
 
@@ -372,6 +546,36 @@ func (b *BunSelectQuery) PreloadRelation(relation string, apply ...func(common.S
 	return b
 }
 
+func (b *BunSelectQuery) JoinRelation(relation string, apply ...func(common.SelectQuery) common.SelectQuery) common.SelectQuery {
+	// JoinRelation uses a LEFT JOIN instead of a separate query
+	// This is more efficient for many-to-one or one-to-one relationships
+
+	logger.Debug("JoinRelation '%s' - Using JOIN strategy with automatic WHERE prefix addition", relation)
+
+	// Wrap the apply functions to automatically add table prefix to WHERE conditions
+	wrappedApply := make([]func(common.SelectQuery) common.SelectQuery, 0, len(apply))
+	for _, fn := range apply {
+		if fn != nil {
+			wrappedFn := func(originalFn func(common.SelectQuery) common.SelectQuery) func(common.SelectQuery) common.SelectQuery {
+				return func(q common.SelectQuery) common.SelectQuery {
+					// Create a special wrapper that adds prefixes to WHERE conditions
+					if bunQuery, ok := q.(*BunSelectQuery); ok {
+						// Mark this query as being in JOIN context
+						bunQuery.inJoinContext = true
+						bunQuery.joinTableAlias = strings.ToLower(relation)
+					}
+					return originalFn(q)
+				}
+			}(fn)
+			wrappedApply = append(wrappedApply, wrappedFn)
+		}
+	}
+
+	// Use PreloadRelation with the wrapped functions
+	// Bun's Relation() will use JOIN for belongs-to and has-one relations
+	return b.PreloadRelation(relation, wrappedApply...)
+}
+
 func (b *BunSelectQuery) Order(order string) common.SelectQuery {
 	b.query = b.query.Order(order)
 	return b
@@ -410,6 +614,9 @@ func (b *BunSelectQuery) Scan(ctx context.Context, dest interface{}) (err error)
 	// Execute the main query first
 	err = b.query.Scan(ctx, dest)
 	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := b.query.String()
+		logger.Error("BunSelectQuery.Scan failed. SQL: %s. Error: %v", sqlStr, err)
 		return err
 	}
 
@@ -438,6 +645,9 @@ func (b *BunSelectQuery) ScanModel(ctx context.Context) (err error) {
 	// Execute the main query first
 	err = b.query.Scan(ctx)
 	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := b.query.String()
+		logger.Error("BunSelectQuery.ScanModel failed. SQL: %s. Error: %v", sqlStr, err)
 		return err
 	}
 
@@ -573,15 +783,25 @@ func (b *BunSelectQuery) Count(ctx context.Context) (count int, err error) {
 	// If Model() was set, use bun's native Count() which works properly
 	if b.hasModel {
 		count, err := b.query.Count(ctx)
+		if err != nil {
+			// Log SQL string for debugging
+			sqlStr := b.query.String()
+			logger.Error("BunSelectQuery.Count failed. SQL: %s. Error: %v", sqlStr, err)
+		}
 		return count, err
 	}
 
 	// Otherwise, wrap as subquery to avoid "Model(nil)" error
 	// This is needed when only Table() is set without a model
-	err = b.db.NewSelect().
+	countQuery := b.db.NewSelect().
 		TableExpr("(?) AS subquery", b.query).
-		ColumnExpr("COUNT(*)").
+		ColumnExpr("COUNT(*)")
-		Scan(ctx, &count)
+	err = countQuery.Scan(ctx, &count)
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := countQuery.String()
+		logger.Error("BunSelectQuery.Count (subquery) failed. SQL: %s. Error: %v", sqlStr, err)
+	}
 	return count, err
 }
 
@@ -592,7 +812,13 @@ func (b *BunSelectQuery) Exists(ctx context.Context) (exists bool, err error) {
 			exists = false
 		}
 	}()
-	return b.query.Exists(ctx)
+	exists, err = b.query.Exists(ctx)
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := b.query.String()
+		logger.Error("BunSelectQuery.Exists failed. SQL: %s. Error: %v", sqlStr, err)
+	}
+	return exists, err
 }
 
 // BunInsertQuery implements InsertQuery for Bun
@@ -729,6 +955,11 @@ func (b *BunUpdateQuery) Exec(ctx context.Context) (res common.Result, err error
 		}
 	}()
 	result, err := b.query.Exec(ctx)
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := b.query.String()
+		logger.Error("BunUpdateQuery.Exec failed. SQL: %s. Error: %v", sqlStr, err)
+	}
 	return &BunResult{result: result}, err
 }
 
@@ -759,6 +990,11 @@ func (b *BunDeleteQuery) Exec(ctx context.Context) (res common.Result, err error
 		}
 	}()
 	result, err := b.query.Exec(ctx)
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := b.query.String()
+		logger.Error("BunDeleteQuery.Exec failed. SQL: %s. Error: %v", sqlStr, err)
+	}
 	return &BunResult{result: result}, err
 }
 

pkg/common/adapters/database/gorm.go

@@ -23,6 +23,22 @@ func NewGormAdapter(db *gorm.DB) *GormAdapter {
 	return &GormAdapter{db: db}
 }
 
+// EnableQueryDebug enables query debugging which logs all SQL queries including preloads
+// This is useful for debugging preload queries that may be failing
+func (g *GormAdapter) EnableQueryDebug() *GormAdapter {
+	g.db = g.db.Debug()
+	logger.Info("GORM query debug mode enabled - all SQL queries will be logged")
+	return g
+}
+
+// DisableQueryDebug disables query debugging
+func (g *GormAdapter) DisableQueryDebug() *GormAdapter {
+	// GORM's Debug() creates a new session, so we need to get the base DB
+	// This is a simplified implementation
+	logger.Info("GORM debug mode - create a new adapter without Debug() to disable")
+	return g
+}
+
 func (g *GormAdapter) NewSelect() common.SelectQuery {
 	return &GormSelectQuery{db: g.db}
 }
@@ -88,10 +104,12 @@ func (g *GormAdapter) RunInTransaction(ctx context.Context, fn func(common.Datab
 
 // GormSelectQuery implements SelectQuery for GORM
 type GormSelectQuery struct {
-	db         *gorm.DB
+	db             *gorm.DB
-	schema     string // Separated schema name
+	schema         string // Separated schema name
-	tableName  string // Just the table name, without schema
+	tableName      string // Just the table name, without schema
-	tableAlias string
+	tableAlias     string
+	inJoinContext  bool   // Track if we're in a JOIN relation context
+	joinTableAlias string // Alias to use for JOIN conditions
 }
 
 func (g *GormSelectQuery) Model(model interface{}) common.SelectQuery {
@@ -135,10 +153,61 @@ func (g *GormSelectQuery) ColumnExpr(query string, args ...interface{}) common.S
 }
 
 func (g *GormSelectQuery) Where(query string, args ...interface{}) common.SelectQuery {
+	// If we're in a JOIN context, add table prefix to unqualified columns
+	if g.inJoinContext && g.joinTableAlias != "" {
+		query = addTablePrefixGorm(query, g.joinTableAlias)
+	}
 	g.db = g.db.Where(query, args...)
 	return g
 }
 
+// addTablePrefixGorm adds a table prefix to unqualified column references (GORM version)
+func addTablePrefixGorm(query, tableAlias string) string {
+	if tableAlias == "" || query == "" {
+		return query
+	}
+
+	// Split on spaces and parentheses to find column references
+	parts := strings.FieldsFunc(query, func(r rune) bool {
+		return r == ' ' || r == '(' || r == ')' || r == ','
+	})
+
+	modified := query
+	for _, part := range parts {
+		// Check if this looks like an unqualified column reference
+		if !strings.Contains(part, ".") {
+			// Extract potential column name (before = or other operators)
+			for _, op := range []string{"=", "!=", "<>", ">", ">=", "<", "<=", " LIKE ", " IN ", " IS "} {
+				if strings.Contains(part, op) {
+					colName := strings.Split(part, op)[0]
+					colName = strings.TrimSpace(colName)
+					if colName != "" && !isOperatorOrKeywordGorm(colName) {
+						// Add table prefix
+						prefixed := tableAlias + "." + colName + strings.TrimPrefix(part, colName)
+						modified = strings.ReplaceAll(modified, part, prefixed)
+						logger.Debug("Adding table prefix '%s' to column '%s' in JOIN condition", tableAlias, colName)
+					}
+					break
+				}
+			}
+		}
+	}
+
+	return modified
+}
+
+// isOperatorOrKeywordGorm checks if a string is likely an operator or SQL keyword (GORM version)
+func isOperatorOrKeywordGorm(s string) bool {
+	s = strings.ToUpper(strings.TrimSpace(s))
+	keywords := []string{"AND", "OR", "NOT", "IN", "IS", "NULL", "TRUE", "FALSE", "LIKE", "BETWEEN"}
+	for _, kw := range keywords {
+		if s == kw {
+			return true
+		}
+	}
+	return false
+}
+
 func (g *GormSelectQuery) WhereOr(query string, args ...interface{}) common.SelectQuery {
 	g.db = g.db.Or(query, args...)
 	return g
@@ -222,6 +291,27 @@ func (g *GormSelectQuery) Preload(relation string, conditions ...interface{}) co
 }
 
 func (g *GormSelectQuery) PreloadRelation(relation string, apply ...func(common.SelectQuery) common.SelectQuery) common.SelectQuery {
+	// Auto-detect relationship type and choose optimal loading strategy
+	// Get the model from GORM's statement if available
+	if g.db.Statement != nil && g.db.Statement.Model != nil {
+		relType := reflection.GetRelationType(g.db.Statement.Model, relation)
+
+		// Log the detected relationship type
+		logger.Debug("PreloadRelation '%s' detected as: %s", relation, relType)
+
+		// If this is a belongs-to or has-one relation, use JOIN for better performance
+		if relType.ShouldUseJoin() {
+			logger.Info("Using JOIN strategy for %s relation '%s'", relType, relation)
+			return g.JoinRelation(relation, apply...)
+		}
+
+		// For has-many, many-to-many, or unknown: use separate query (safer default)
+		if relType == reflection.RelationHasMany || relType == reflection.RelationManyToMany {
+			logger.Debug("Using separate query for %s relation '%s'", relType, relation)
+		}
+	}
+
+	// Use GORM's Preload (separate query strategy)
 	g.db = g.db.Preload(relation, func(db *gorm.DB) *gorm.DB {
 		if len(apply) == 0 {
 			return db
@@ -251,6 +341,42 @@ func (g *GormSelectQuery) PreloadRelation(relation string, apply ...func(common.
 	return g
 }
 
+func (g *GormSelectQuery) JoinRelation(relation string, apply ...func(common.SelectQuery) common.SelectQuery) common.SelectQuery {
+	// JoinRelation uses a JOIN instead of a separate preload query
+	// This is more efficient for many-to-one or one-to-one relationships
+	// as it avoids additional round trips to the database
+
+	// GORM's Joins() method forces a JOIN for the preload
+	logger.Debug("JoinRelation '%s' - Using GORM Joins() with automatic WHERE prefix addition", relation)
+
+	g.db = g.db.Joins(relation, func(db *gorm.DB) *gorm.DB {
+		if len(apply) == 0 {
+			return db
+		}
+
+		wrapper := &GormSelectQuery{
+			db:             db,
+			inJoinContext:  true,                      // Mark as JOIN context
+			joinTableAlias: strings.ToLower(relation), // Use relation name as alias
+		}
+		current := common.SelectQuery(wrapper)
+
+		for _, fn := range apply {
+			if fn != nil {
+				current = fn(current)
+			}
+		}
+
+		if finalGorm, ok := current.(*GormSelectQuery); ok {
+			return finalGorm.db
+		}
+
+		return db
+	})
+
+	return g
+}
+
 func (g *GormSelectQuery) Order(order string) common.SelectQuery {
 	g.db = g.db.Order(order)
 	return g
@@ -282,7 +408,15 @@ func (g *GormSelectQuery) Scan(ctx context.Context, dest interface{}) (err error
 			err = logger.HandlePanic("GormSelectQuery.Scan", r)
 		}
 	}()
-	return g.db.WithContext(ctx).Find(dest).Error
+	err = g.db.WithContext(ctx).Find(dest).Error
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := g.db.ToSQL(func(tx *gorm.DB) *gorm.DB {
+			return tx.Find(dest)
+		})
+		logger.Error("GormSelectQuery.Scan failed. SQL: %s. Error: %v", sqlStr, err)
+	}
+	return err
 }
 
 func (g *GormSelectQuery) ScanModel(ctx context.Context) (err error) {
@@ -294,7 +428,15 @@ func (g *GormSelectQuery) ScanModel(ctx context.Context) (err error) {
 	if g.db.Statement.Model == nil {
 		return fmt.Errorf("ScanModel requires Model() to be set before scanning")
 	}
-	return g.db.WithContext(ctx).Find(g.db.Statement.Model).Error
+	err = g.db.WithContext(ctx).Find(g.db.Statement.Model).Error
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := g.db.ToSQL(func(tx *gorm.DB) *gorm.DB {
+			return tx.Find(g.db.Statement.Model)
+		})
+		logger.Error("GormSelectQuery.ScanModel failed. SQL: %s. Error: %v", sqlStr, err)
+	}
+	return err
 }
 
 func (g *GormSelectQuery) Count(ctx context.Context) (count int, err error) {
@@ -306,6 +448,13 @@ func (g *GormSelectQuery) Count(ctx context.Context) (count int, err error) {
 	}()
 	var count64 int64
 	err = g.db.WithContext(ctx).Count(&count64).Error
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := g.db.ToSQL(func(tx *gorm.DB) *gorm.DB {
+			return tx.Count(&count64)
+		})
+		logger.Error("GormSelectQuery.Count failed. SQL: %s. Error: %v", sqlStr, err)
+	}
 	return int(count64), err
 }
 
@@ -318,6 +467,13 @@ func (g *GormSelectQuery) Exists(ctx context.Context) (exists bool, err error) {
 	}()
 	var count int64
 	err = g.db.WithContext(ctx).Limit(1).Count(&count).Error
+	if err != nil {
+		// Log SQL string for debugging
+		sqlStr := g.db.ToSQL(func(tx *gorm.DB) *gorm.DB {
+			return tx.Limit(1).Count(&count)
+		})
+		logger.Error("GormSelectQuery.Exists failed. SQL: %s. Error: %v", sqlStr, err)
+	}
 	return count > 0, err
 }
 
@@ -456,6 +612,13 @@ func (g *GormUpdateQuery) Exec(ctx context.Context) (res common.Result, err erro
 		}
 	}()
 	result := g.db.WithContext(ctx).Updates(g.updates)
+	if result.Error != nil {
+		// Log SQL string for debugging
+		sqlStr := g.db.ToSQL(func(tx *gorm.DB) *gorm.DB {
+			return tx.Updates(g.updates)
+		})
+		logger.Error("GormUpdateQuery.Exec failed. SQL: %s. Error: %v", sqlStr, result.Error)
+	}
 	return &GormResult{result: result}, result.Error
 }
 
@@ -488,6 +651,13 @@ func (g *GormDeleteQuery) Exec(ctx context.Context) (res common.Result, err erro
 		}
 	}()
 	result := g.db.WithContext(ctx).Delete(g.model)
+	if result.Error != nil {
+		// Log SQL string for debugging
+		sqlStr := g.db.ToSQL(func(tx *gorm.DB) *gorm.DB {
+			return tx.Delete(g.model)
+		})
+		logger.Error("GormDeleteQuery.Exec failed. SQL: %s. Error: %v", sqlStr, result.Error)
+	}
 	return &GormResult{result: result}, result.Error
 }
 

pkg/common/interfaces.go

@@ -38,6 +38,7 @@ type SelectQuery interface {
 	LeftJoin(query string, args ...interface{}) SelectQuery
 	Preload(relation string, conditions ...interface{}) SelectQuery
 	PreloadRelation(relation string, apply ...func(SelectQuery) SelectQuery) SelectQuery
+	JoinRelation(relation string, apply ...func(SelectQuery) SelectQuery) SelectQuery
 	Order(order string) SelectQuery
 	Limit(n int) SelectQuery
 	Offset(n int) SelectQuery

pkg/common/sql_helpers.go

@@ -1,7 +1,6 @@
 package common
 
 import (
-	"fmt"
 	"strings"
 
 	"github.com/bitechdev/ResolveSpec/pkg/logger"
@@ -9,81 +8,40 @@ import (
 	"github.com/bitechdev/ResolveSpec/pkg/reflection"
 )
 
-// ValidateAndFixPreloadWhere validates that the WHERE clause for a preload contains
+// ValidateAndFixPreloadWhere validates and normalizes WHERE clauses for preloads
-// the relation prefix (alias). If not present, it attempts to add it to column references.
+//
-// Returns the fixed WHERE clause and an error if it cannot be safely fixed.
+// NOTE: For preload queries, table aliases from the parent query are not valid since
+// the preload executes as a separate query with its own table alias. This function
+// now simply validates basic syntax without requiring or adding prefixes.
+// The actual alias normalization happens in the database adapter layer.
+//
+// Returns the WHERE clause and an error if it contains obviously invalid syntax.
 func ValidateAndFixPreloadWhere(where string, relationName string) (string, error) {
 	if where == "" {
 		return where, nil
 	}
 
-	// Check if the relation name is already present in the WHERE clause
+	where = strings.TrimSpace(where)
-	lowerWhere := strings.ToLower(where)
-	lowerRelation := strings.ToLower(relationName)
 
-	// Check for patterns like "relation.", "relation ", or just "relation" followed by a dot
+	// Just do basic validation - don't require or add prefixes
-	if strings.Contains(lowerWhere, lowerRelation+".") ||
+	// The database adapter will handle alias normalization
-		strings.Contains(lowerWhere, "`"+lowerRelation+"`.") ||
+
-		strings.Contains(lowerWhere, "\""+lowerRelation+"\".") {
+	// Check if the WHERE clause contains any qualified column references
-		// Relation prefix is already present
+	// If it does, log a debug message but don't fail - let the adapter handle it
+	if strings.Contains(where, ".") {
+		logger.Debug("Preload WHERE clause for '%s' contains qualified column references: '%s'. "+
+			"Note: In preload context, table aliases from parent query are not available. "+
+			"The database adapter will normalize aliases automatically.", relationName, where)
+	}
+
+	// Validate that it's not empty or just whitespace
+	if where == "" {
 		return where, nil
 	}
 
-	// If the WHERE clause is complex (contains OR, parentheses, subqueries, etc.),
+	// Return the WHERE clause as-is
-	// we can't safely auto-fix it - require explicit prefix
+	// The BunSelectQuery.Where() method will handle alias normalization via normalizeTableAlias()
-	if strings.Contains(lowerWhere, " or ") ||
+	return where, nil
-		strings.Contains(where, "(") ||
-		strings.Contains(where, ")") {
-		return "", fmt.Errorf("preload WHERE condition must reference the relation '%s' (e.g., '%s.column_name'). Complex WHERE clauses with OR/parentheses must explicitly use the relation prefix", relationName, relationName)
-	}
-
-	// Try to add the relation prefix to simple column references
-	// This handles basic cases like "column = value" or "column = value AND other_column = value"
-	// Split by AND to handle multiple conditions (case-insensitive)
-	originalConditions := strings.Split(where, " AND ")
-
-	// If uppercase split didn't work, try lowercase
-	if len(originalConditions) == 1 {
-		originalConditions = strings.Split(where, " and ")
-	}
-
-	fixedConditions := make([]string, 0, len(originalConditions))
-
-	for _, cond := range originalConditions {
-		cond = strings.TrimSpace(cond)
-		if cond == "" {
-			continue
-		}
-
-		// Check if this condition already has a table prefix (contains a dot)
-		if strings.Contains(cond, ".") {
-			fixedConditions = append(fixedConditions, cond)
-			continue
-		}
-
-		// Check if this is a SQL expression/literal that shouldn't be prefixed
-		lowerCond := strings.ToLower(strings.TrimSpace(cond))
-		if IsSQLExpression(lowerCond) {
-			// Don't prefix SQL expressions like "true", "false", "1=1", etc.
-			fixedConditions = append(fixedConditions, cond)
-			continue
-		}
-
-		// Extract the column name (first identifier before operator)
-		columnName := ExtractColumnName(cond)
-		if columnName == "" {
-			// Can't identify column name, require explicit prefix
-			return "", fmt.Errorf("preload WHERE condition must reference the relation '%s' (e.g., '%s.column_name'). Cannot auto-fix condition: %s", relationName, relationName, cond)
-		}
-
-		// Add relation prefix to the column name only
-		fixedCond := strings.Replace(cond, columnName, relationName+"."+columnName, 1)
-		fixedConditions = append(fixedConditions, fixedCond)
-	}
-
-	fixedWhere := strings.Join(fixedConditions, " AND ")
-	logger.Debug("Auto-fixed preload WHERE clause: '%s' -> '%s'", where, fixedWhere)
-	return fixedWhere, nil
 }
 
 // IsSQLExpression checks if a condition is a SQL expression that shouldn't be prefixed

pkg/common/sql_types.go

@@ -71,15 +71,14 @@ func (n *SqlNull[T]) Scan(value any) error {
 	// Fallback: parse from string/bytes.
 	switch v := value.(type) {
 	case string:
-		return n.fromString(v)
+		return n.FromString(v)
 	case []byte:
-		return n.fromString(string(v))
+		return n.FromString(string(v))
 	default:
-		return n.fromString(fmt.Sprintf("%v", value))
+		return n.FromString(fmt.Sprintf("%v", value))
 	}
 }
-
+func (n *SqlNull[T]) FromString(s string) error {
-func (n *SqlNull[T]) fromString(s string) error {
 	s = strings.TrimSpace(s)
 	n.Valid = false
 	n.Val = *new(T)
@@ -90,19 +89,14 @@ func (n *SqlNull[T]) fromString(s string) error {
 
 	var zero T
 	switch any(zero).(type) {
-	case int, int8, int16, int32, int64:
+	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
 		if i, err := strconv.ParseInt(s, 10, 64); err == nil {
-			n.Val = any(int64(i)).(T) // Cast to T (e.g., int16)
+			reflect.ValueOf(&n.Val).Elem().SetInt(i)
-			n.Valid = true
-		}
-	case uint, uint8, uint16, uint32, uint64:
-		if u, err := strconv.ParseUint(s, 10, 64); err == nil {
-			n.Val = any(u).(T)
 			n.Valid = true
 		}
 	case float32, float64:
 		if f, err := strconv.ParseFloat(s, 64); err == nil {
-			n.Val = any(f).(T)
+			reflect.ValueOf(&n.Val).Elem().SetFloat(f)
 			n.Valid = true
 		}
 	case bool:
@@ -124,7 +118,6 @@ func (n *SqlNull[T]) fromString(s string) error {
 		n.Val = any(s).(T)
 		n.Valid = true
 	}
-
 	return nil
 }
 
@@ -163,7 +156,7 @@ func (n *SqlNull[T]) UnmarshalJSON(b []byte) error {
 	// Fallback: unmarshal as string and parse.
 	var s string
 	if err := json.Unmarshal(b, &s); err == nil {
-		return n.fromString(s)
+		return n.FromString(s)
 	}
 
 	return fmt.Errorf("cannot unmarshal %s into SqlNull[%T]", b, n.Val)
@@ -517,6 +510,33 @@ func TryIfInt64(v any, def int64) int64 {
 }
 
 // Constructor helpers - clean and fast value creation
+func Null[T any](v T, valid bool) SqlNull[T] {
+	return SqlNull[T]{Val: v, Valid: valid}
+}
+
+func NewSql[T any](value any) SqlNull[T] {
+	n := SqlNull[T]{}
+
+	if value == nil {
+		return n
+	}
+
+	// Fast path: exact match
+	if v, ok := value.(T); ok {
+		n.Val = v
+		n.Valid = true
+		return n
+	}
+
+	// Try from another SqlNull
+	if sn, ok := value.(SqlNull[T]); ok {
+		return sn
+	}
+
+	// Convert via string
+	_ = n.FromString(fmt.Sprintf("%v", value))
+	return n
+}
 
 func NewSqlInt16(v int16) SqlInt16 {
 	return SqlInt16{Val: v, Valid: true}

pkg/common/sql_types_test.go

@@ -16,11 +16,11 @@ func TestNewSqlInt16(t *testing.T) {
 		input    interface{}
 		expected SqlInt16
 	}{
-		{"int", 42, NewSqlInt16(42)},
+		{"int", 42, Null(int16(42), true)},
 		{"int32", int32(100), NewSqlInt16(100)},
 		{"int64", int64(200), NewSqlInt16(200)},
 		{"string", "123", NewSqlInt16(123)},
-		{"nil", nil, NewSqlInt16(0)},
+		{"nil", nil, Null(int16(0), false)},
 	}
 
 	for _, tt := range tests {
@@ -42,9 +42,9 @@ func TestNewSqlInt16_Value(t *testing.T) {
 		input    SqlInt16
 		expected driver.Value
 	}{
-		{"zero", NewSqlInt16(0), nil},
+		{"zero", Null(int16(0), false), nil},
-		{"positive", NewSqlInt16(42), int64(42)},
+		{"positive", NewSqlInt16(42), int16(42)},
-		{"negative", NewSqlInt16(-10), int64(-10)},
+		{"negative", NewSqlInt16(-10), int16(-10)},
 	}
 
 	for _, tt := range tests {
@@ -486,7 +486,7 @@ func TestSqlUUID_Value(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Value failed: %v", err)
 	}
-	if val != testUUID.String() {
+	if val != testUUID {
 		t.Errorf("expected %s, got %s", testUUID.String(), val)
 	}
 

pkg/funcspec/function_api_test.go

@@ -16,8 +16,8 @@ import (
 
 // MockDatabase implements common.Database interface for testing
 type MockDatabase struct {
-	QueryFunc          func(ctx context.Context, dest interface{}, query string, args ...interface{}) error
+	QueryFunc            func(ctx context.Context, dest interface{}, query string, args ...interface{}) error
-	ExecFunc           func(ctx context.Context, query string, args ...interface{}) (common.Result, error)
+	ExecFunc             func(ctx context.Context, query string, args ...interface{}) (common.Result, error)
 	RunInTransactionFunc func(ctx context.Context, fn func(common.Database) error) error
 }
 
@@ -161,9 +161,9 @@ func TestExtractInputVariables(t *testing.T) {
 	handler := NewHandler(&MockDatabase{})
 
 	tests := []struct {
-		name          string
+		name         string
-		sqlQuery      string
+		sqlQuery     string
-		expectedVars  []string
+		expectedVars []string
 	}{
 		{
 			name:         "No variables",
@@ -340,9 +340,9 @@ func TestSqlQryWhere(t *testing.T) {
 // TestGetIPAddress tests IP address extraction
 func TestGetIPAddress(t *testing.T) {
 	tests := []struct {
-		name      string
+		name     string
-		setupReq  func() *http.Request
+		setupReq func() *http.Request
-		expected  string
+		expected string
 	}{
 		{
 			name: "X-Forwarded-For header",
@@ -782,9 +782,10 @@ func TestReplaceMetaVariables(t *testing.T) {
 	handler := NewHandler(&MockDatabase{})
 
 	userCtx := &security.UserContext{
-		UserID:    123,
+		UserID:     123,
-		UserName:  "testuser",
+		UserName:   "testuser",
-		SessionID: "456",
+		SessionID:  "ABC456",
+		SessionRID: 456,
 	}
 
 	metainfo := map[string]interface{}{
@@ -821,6 +822,12 @@ func TestReplaceMetaVariables(t *testing.T) {
 			expectedCheck: func(result string) bool {
 				return strings.Contains(result, "456")
 			},
+		}, {
+			name:     "Replace [id_session]",
+			sqlQuery: "SELECT * FROM sessions WHERE session_id = [id_session]",
+			expectedCheck: func(result string) bool {
+				return strings.Contains(result, "ABC456")
+			},
 		},
 	}
 

pkg/reflection/model_utils.go

@@ -750,6 +750,118 @@ func ConvertToNumericType(value string, kind reflect.Kind) (interface{}, error)
 	return nil, fmt.Errorf("unsupported numeric type: %v", kind)
 }
 
+// RelationType represents the type of database relationship
+type RelationType string
+
+const (
+	RelationHasMany    RelationType = "has-many"     // 1:N - use separate query
+	RelationBelongsTo  RelationType = "belongs-to"   // N:1 - use JOIN
+	RelationHasOne     RelationType = "has-one"      // 1:1 - use JOIN
+	RelationManyToMany RelationType = "many-to-many" // M:N - use separate query
+	RelationUnknown    RelationType = "unknown"
+)
+
+// ShouldUseJoin returns true if the relation type should use a JOIN instead of separate query
+func (rt RelationType) ShouldUseJoin() bool {
+	return rt == RelationBelongsTo || rt == RelationHasOne
+}
+
+// GetRelationType inspects the model's struct tags to determine the relationship type
+// It checks both Bun and GORM tags to identify the relationship cardinality
+func GetRelationType(model interface{}, fieldName string) RelationType {
+	if model == nil || fieldName == "" {
+		return RelationUnknown
+	}
+
+	modelType := reflect.TypeOf(model)
+	if modelType == nil {
+		return RelationUnknown
+	}
+
+	if modelType.Kind() == reflect.Ptr {
+		modelType = modelType.Elem()
+	}
+
+	if modelType == nil || modelType.Kind() != reflect.Struct {
+		return RelationUnknown
+	}
+
+	// Find the field
+	for i := 0; i < modelType.NumField(); i++ {
+		field := modelType.Field(i)
+
+		// Check if field name matches (case-insensitive)
+		if !strings.EqualFold(field.Name, fieldName) {
+			continue
+		}
+
+		// Check Bun tags first
+		bunTag := field.Tag.Get("bun")
+		if bunTag != "" && strings.Contains(bunTag, "rel:") {
+			// Parse bun relation tag: rel:has-many, rel:belongs-to, rel:has-one, rel:many-to-many
+			parts := strings.Split(bunTag, ",")
+			for _, part := range parts {
+				part = strings.TrimSpace(part)
+				if strings.HasPrefix(part, "rel:") {
+					relType := strings.TrimPrefix(part, "rel:")
+					switch relType {
+					case "has-many":
+						return RelationHasMany
+					case "belongs-to":
+						return RelationBelongsTo
+					case "has-one":
+						return RelationHasOne
+					case "many-to-many", "m2m":
+						return RelationManyToMany
+					}
+				}
+			}
+		}
+
+		// Check GORM tags
+		gormTag := field.Tag.Get("gorm")
+		if gormTag != "" {
+			// GORM uses different patterns:
+			// - foreignKey: usually indicates belongs-to or has-one
+			// - many2many: indicates many-to-many
+			// - Field type (slice vs pointer) helps determine cardinality
+
+			if strings.Contains(gormTag, "many2many:") {
+				return RelationManyToMany
+			}
+
+			// Check field type for cardinality hints
+			fieldType := field.Type
+			if fieldType.Kind() == reflect.Slice {
+				// Slice indicates has-many or many-to-many
+				return RelationHasMany
+			}
+			if fieldType.Kind() == reflect.Ptr {
+				// Pointer to single struct usually indicates belongs-to or has-one
+				// Check if it has foreignKey (belongs-to) or references (has-one)
+				if strings.Contains(gormTag, "foreignKey:") {
+					return RelationBelongsTo
+				}
+				return RelationHasOne
+			}
+		}
+
+		// Fall back to field type inference
+		fieldType := field.Type
+		if fieldType.Kind() == reflect.Slice {
+			// Slice of structs → has-many
+			return RelationHasMany
+		}
+		if fieldType.Kind() == reflect.Ptr || fieldType.Kind() == reflect.Struct {
+			// Single struct → belongs-to (default assumption for safety)
+			// Using belongs-to as default ensures we use JOIN, which is safer
+			return RelationBelongsTo
+		}
+	}
+
+	return RelationUnknown
+}
+
 // GetRelationModel gets the model type for a relation field
 // It searches for the field by name in the following order (case-insensitive):
 // 1. Actual field name