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				| package engine | |
| 
 | |
| import ( | |
| 	"context" | |
| 	"strconv" | |
| 	"strings" | |
| 	"testing" | |
| ) | |
| 
 | |
| // TestParseSQL_OFFSET_EdgeCases tests edge cases for OFFSET parsing | |
| func TestParseSQL_OFFSET_EdgeCases(t *testing.T) { | |
| 	tests := []struct { | |
| 		name     string | |
| 		sql      string | |
| 		wantErr  bool | |
| 		validate func(t *testing.T, stmt Statement, err error) | |
| 	}{ | |
| 		{ | |
| 			name:    "Valid LIMIT OFFSET with WHERE", | |
| 			sql:     "SELECT * FROM users WHERE age > 18 LIMIT 10 OFFSET 5", | |
| 			wantErr: false, | |
| 			validate: func(t *testing.T, stmt Statement, err error) { | |
| 				selectStmt := stmt.(*SelectStatement) | |
| 				if selectStmt.Limit == nil { | |
| 					t.Fatal("Expected LIMIT clause, got nil") | |
| 				} | |
| 				if selectStmt.Limit.Offset == nil { | |
| 					t.Fatal("Expected OFFSET clause, got nil") | |
| 				} | |
| 				if selectStmt.Where == nil { | |
| 					t.Fatal("Expected WHERE clause, got nil") | |
| 				} | |
| 			}, | |
| 		}, | |
| 		{ | |
| 			name:    "LIMIT OFFSET with mixed case", | |
| 			sql:     "select * from users limit 5 offset 3", | |
| 			wantErr: false, | |
| 			validate: func(t *testing.T, stmt Statement, err error) { | |
| 				selectStmt := stmt.(*SelectStatement) | |
| 				offsetVal := selectStmt.Limit.Offset.(*SQLVal) | |
| 				if string(offsetVal.Val) != "3" { | |
| 					t.Errorf("Expected offset value '3', got '%s'", string(offsetVal.Val)) | |
| 				} | |
| 			}, | |
| 		}, | |
| 		{ | |
| 			name:    "LIMIT OFFSET with extra spaces", | |
| 			sql:     "SELECT * FROM users LIMIT   10   OFFSET   20  ", | |
| 			wantErr: false, | |
| 			validate: func(t *testing.T, stmt Statement, err error) { | |
| 				selectStmt := stmt.(*SelectStatement) | |
| 				limitVal := selectStmt.Limit.Rowcount.(*SQLVal) | |
| 				offsetVal := selectStmt.Limit.Offset.(*SQLVal) | |
| 				if string(limitVal.Val) != "10" { | |
| 					t.Errorf("Expected limit value '10', got '%s'", string(limitVal.Val)) | |
| 				} | |
| 				if string(offsetVal.Val) != "20" { | |
| 					t.Errorf("Expected offset value '20', got '%s'", string(offsetVal.Val)) | |
| 				} | |
| 			}, | |
| 		}, | |
| 	} | |
| 
 | |
| 	for _, tt := range tests { | |
| 		t.Run(tt.name, func(t *testing.T) { | |
| 			stmt, err := ParseSQL(tt.sql) | |
| 
 | |
| 			if tt.wantErr { | |
| 				if err == nil { | |
| 					t.Errorf("Expected error, but got none") | |
| 				} | |
| 				return | |
| 			} | |
| 
 | |
| 			if err != nil { | |
| 				t.Errorf("Unexpected error: %v", err) | |
| 				return | |
| 			} | |
| 
 | |
| 			if tt.validate != nil { | |
| 				tt.validate(t, stmt, err) | |
| 			} | |
| 		}) | |
| 	} | |
| } | |
| 
 | |
| // TestSQLEngine_OFFSET_EdgeCases tests edge cases for OFFSET execution | |
| func TestSQLEngine_OFFSET_EdgeCases(t *testing.T) { | |
| 	engine := NewTestSQLEngine() | |
| 
 | |
| 	t.Run("OFFSET larger than result set", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT * FROM user_events LIMIT 5 OFFSET 100") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 		// Should return empty result set | |
| 		if len(result.Rows) != 0 { | |
| 			t.Errorf("Expected 0 rows when OFFSET > total rows, got %d", len(result.Rows)) | |
| 		} | |
| 	}) | |
| 
 | |
| 	t.Run("OFFSET with LIMIT 0", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT * FROM user_events LIMIT 0 OFFSET 2") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 		// LIMIT 0 should return no rows regardless of OFFSET | |
| 		if len(result.Rows) != 0 { | |
| 			t.Errorf("Expected 0 rows with LIMIT 0, got %d", len(result.Rows)) | |
| 		} | |
| 	}) | |
| 
 | |
| 	t.Run("High OFFSET with small LIMIT", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT * FROM user_events LIMIT 1 OFFSET 3") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 		// In clean mock environment, we have 4 live_log rows from unflushed messages | |
| 		// LIMIT 1 OFFSET 3 should return the 4th row (0-indexed: rows 0,1,2,3 -> return row 3) | |
| 		if len(result.Rows) != 1 { | |
| 			t.Errorf("Expected 1 row with LIMIT 1 OFFSET 3 (4th live_log row), got %d", len(result.Rows)) | |
| 		} | |
| 	}) | |
| } | |
| 
 | |
| // TestSQLEngine_OFFSET_ErrorCases tests error conditions for OFFSET | |
| func TestSQLEngine_OFFSET_ErrorCases(t *testing.T) { | |
| 	engine := NewTestSQLEngine() | |
| 
 | |
| 	// Test negative OFFSET - should be caught during execution | |
| 	t.Run("Negative OFFSET value", func(t *testing.T) { | |
| 		// Note: This would need to be implemented as validation in the execution engine | |
| 		// For now, we test that the parser accepts it but execution might handle it | |
| 		_, err := ParseSQL("SELECT * FROM users LIMIT 10 OFFSET -5") | |
| 		if err != nil { | |
| 			t.Logf("Parser rejected negative OFFSET (this is expected): %v", err) | |
| 		} else { | |
| 			// Parser accepts it, execution should handle validation | |
| 			t.Logf("Parser accepts negative OFFSET, execution should validate") | |
| 		} | |
| 	}) | |
| 
 | |
| 	// Test very large OFFSET | |
| 	t.Run("Very large OFFSET value", func(t *testing.T) { | |
| 		largeOffset := "2147483647" // Max int32 | |
| 		sql := "SELECT * FROM user_events LIMIT 1 OFFSET " + largeOffset | |
| 		result, err := engine.ExecuteSQL(context.Background(), sql) | |
| 		if err != nil { | |
| 			// Large OFFSET might cause parsing or execution errors | |
| 			if strings.Contains(err.Error(), "out of valid range") { | |
| 				t.Logf("Large OFFSET properly rejected: %v", err) | |
| 			} else { | |
| 				t.Errorf("Unexpected error for large OFFSET: %v", err) | |
| 			} | |
| 		} else if result.Error != nil { | |
| 			if strings.Contains(result.Error.Error(), "out of valid range") { | |
| 				t.Logf("Large OFFSET properly rejected during execution: %v", result.Error) | |
| 			} else { | |
| 				t.Errorf("Unexpected execution error for large OFFSET: %v", result.Error) | |
| 			} | |
| 		} else { | |
| 			// Should return empty result for very large offset | |
| 			if len(result.Rows) != 0 { | |
| 				t.Errorf("Expected 0 rows for very large OFFSET, got %d", len(result.Rows)) | |
| 			} | |
| 		} | |
| 	}) | |
| } | |
| 
 | |
| // TestSQLEngine_OFFSET_Consistency tests that OFFSET produces consistent results | |
| func TestSQLEngine_OFFSET_Consistency(t *testing.T) { | |
| 	engine := NewTestSQLEngine() | |
| 
 | |
| 	// Get all rows first | |
| 	allResult, err := engine.ExecuteSQL(context.Background(), "SELECT * FROM user_events") | |
| 	if err != nil { | |
| 		t.Fatalf("Failed to get all rows: %v", err) | |
| 	} | |
| 	if allResult.Error != nil { | |
| 		t.Fatalf("Failed to get all rows: %v", allResult.Error) | |
| 	} | |
| 
 | |
| 	totalRows := len(allResult.Rows) | |
| 	if totalRows == 0 { | |
| 		t.Skip("No data available for consistency test") | |
| 	} | |
| 
 | |
| 	// Test that OFFSET + remaining rows = total rows | |
| 	for offset := 0; offset < totalRows; offset++ { | |
| 		t.Run("OFFSET_"+strconv.Itoa(offset), func(t *testing.T) { | |
| 			sql := "SELECT * FROM user_events LIMIT 100 OFFSET " + strconv.Itoa(offset) | |
| 			result, err := engine.ExecuteSQL(context.Background(), sql) | |
| 			if err != nil { | |
| 				t.Fatalf("Error with OFFSET %d: %v", offset, err) | |
| 			} | |
| 			if result.Error != nil { | |
| 				t.Fatalf("Query error with OFFSET %d: %v", offset, result.Error) | |
| 			} | |
| 
 | |
| 			expectedRows := totalRows - offset | |
| 			if len(result.Rows) != expectedRows { | |
| 				t.Errorf("OFFSET %d: expected %d rows, got %d", offset, expectedRows, len(result.Rows)) | |
| 			} | |
| 		}) | |
| 	} | |
| } | |
| 
 | |
| // TestSQLEngine_LIMIT_OFFSET_BugFix tests the specific bug fix for LIMIT with OFFSET | |
| // This test addresses the issue where LIMIT 10 OFFSET 5 was returning 5 rows instead of 10 | |
| func TestSQLEngine_LIMIT_OFFSET_BugFix(t *testing.T) { | |
| 	engine := NewTestSQLEngine() | |
| 
 | |
| 	// Test the specific scenario that was broken: LIMIT 10 OFFSET 5 should return 10 rows | |
| 	t.Run("LIMIT 10 OFFSET 5 returns correct count", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT id, user_id, id+user_id FROM user_events LIMIT 10 OFFSET 5") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 
 | |
| 		// The bug was that this returned 5 rows instead of 10 | |
| 		// After fix, it should return up to 10 rows (limited by available data) | |
| 		actualRows := len(result.Rows) | |
| 		if actualRows > 10 { | |
| 			t.Errorf("LIMIT 10 violated: got %d rows", actualRows) | |
| 		} | |
| 
 | |
| 		t.Logf("LIMIT 10 OFFSET 5 returned %d rows (within limit)", actualRows) | |
| 
 | |
| 		// Verify we have the expected columns | |
| 		expectedCols := 3 // id, user_id, id+user_id | |
| 		if len(result.Columns) != expectedCols { | |
| 			t.Errorf("Expected %d columns, got %d columns: %v", expectedCols, len(result.Columns), result.Columns) | |
| 		} | |
| 	}) | |
| 
 | |
| 	// Test various LIMIT and OFFSET combinations to ensure correct row counts | |
| 	testCases := []struct { | |
| 		name       string | |
| 		limit      int | |
| 		offset     int | |
| 		allowEmpty bool // Whether 0 rows is acceptable (for large offsets) | |
| 	}{ | |
| 		{"LIMIT 5 OFFSET 0", 5, 0, false}, | |
| 		{"LIMIT 5 OFFSET 2", 5, 2, false}, | |
| 		{"LIMIT 8 OFFSET 3", 8, 3, false}, | |
| 		{"LIMIT 15 OFFSET 1", 15, 1, false}, | |
| 		{"LIMIT 3 OFFSET 7", 3, 7, true},   // Large offset may exceed data | |
| 		{"LIMIT 12 OFFSET 4", 12, 4, true}, // Large offset may exceed data | |
| 	} | |
| 
 | |
| 	for _, tc := range testCases { | |
| 		t.Run(tc.name, func(t *testing.T) { | |
| 			sql := "SELECT id, user_id FROM user_events LIMIT " + strconv.Itoa(tc.limit) + " OFFSET " + strconv.Itoa(tc.offset) | |
| 			result, err := engine.ExecuteSQL(context.Background(), sql) | |
| 			if err != nil { | |
| 				t.Fatalf("Expected no error for %s, got %v", tc.name, err) | |
| 			} | |
| 			if result.Error != nil { | |
| 				t.Fatalf("Expected no query error for %s, got %v", tc.name, result.Error) | |
| 			} | |
| 
 | |
| 			actualRows := len(result.Rows) | |
| 
 | |
| 			// Verify LIMIT is never exceeded | |
| 			if actualRows > tc.limit { | |
| 				t.Errorf("%s: LIMIT violated - returned %d rows, limit was %d", tc.name, actualRows, tc.limit) | |
| 			} | |
| 
 | |
| 			// Check if we expect rows | |
| 			if !tc.allowEmpty && actualRows == 0 { | |
| 				t.Errorf("%s: expected some rows but got 0 (insufficient test data or early termination bug)", tc.name) | |
| 			} | |
| 
 | |
| 			t.Logf("%s: returned %d rows (within limit %d)", tc.name, actualRows, tc.limit) | |
| 		}) | |
| 	} | |
| } | |
| 
 | |
| // TestSQLEngine_OFFSET_DataCollectionBuffer tests that the enhanced data collection buffer works | |
| func TestSQLEngine_OFFSET_DataCollectionBuffer(t *testing.T) { | |
| 	engine := NewTestSQLEngine() | |
| 
 | |
| 	// Test scenarios that specifically stress the data collection buffer enhancement | |
| 	t.Run("Large OFFSET with small LIMIT", func(t *testing.T) { | |
| 		// This scenario requires collecting more data upfront to handle the offset | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT * FROM user_events LIMIT 2 OFFSET 8") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 
 | |
| 		// Should either return 2 rows or 0 (if offset exceeds available data) | |
| 		// The bug would cause early termination and return 0 incorrectly | |
| 		actualRows := len(result.Rows) | |
| 		if actualRows != 0 && actualRows != 2 { | |
| 			t.Errorf("Expected 0 or 2 rows for LIMIT 2 OFFSET 8, got %d", actualRows) | |
| 		} | |
| 	}) | |
| 
 | |
| 	t.Run("Medium OFFSET with medium LIMIT", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT id, user_id FROM user_events LIMIT 6 OFFSET 4") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 
 | |
| 		// With proper buffer enhancement, this should work correctly | |
| 		actualRows := len(result.Rows) | |
| 		if actualRows > 6 { | |
| 			t.Errorf("LIMIT 6 should never return more than 6 rows, got %d", actualRows) | |
| 		} | |
| 	}) | |
| 
 | |
| 	t.Run("Progressive OFFSET test", func(t *testing.T) { | |
| 		// Test that increasing OFFSET values work consistently | |
| 		baseSQL := "SELECT id FROM user_events LIMIT 3 OFFSET " | |
| 
 | |
| 		for offset := 0; offset <= 5; offset++ { | |
| 			sql := baseSQL + strconv.Itoa(offset) | |
| 			result, err := engine.ExecuteSQL(context.Background(), sql) | |
| 			if err != nil { | |
| 				t.Fatalf("Error at OFFSET %d: %v", offset, err) | |
| 			} | |
| 			if result.Error != nil { | |
| 				t.Fatalf("Query error at OFFSET %d: %v", offset, result.Error) | |
| 			} | |
| 
 | |
| 			actualRows := len(result.Rows) | |
| 			// Each should return at most 3 rows (LIMIT 3) | |
| 			if actualRows > 3 { | |
| 				t.Errorf("OFFSET %d: LIMIT 3 returned %d rows (should be ≤ 3)", offset, actualRows) | |
| 			} | |
| 
 | |
| 			t.Logf("OFFSET %d: returned %d rows", offset, actualRows) | |
| 		} | |
| 	}) | |
| } | |
| 
 | |
| // TestSQLEngine_LIMIT_OFFSET_ArithmeticExpressions tests LIMIT/OFFSET with arithmetic expressions | |
| func TestSQLEngine_LIMIT_OFFSET_ArithmeticExpressions(t *testing.T) { | |
| 	engine := NewTestSQLEngine() | |
| 
 | |
| 	// Test the exact scenario from the user's example | |
| 	t.Run("Arithmetic expressions with LIMIT OFFSET", func(t *testing.T) { | |
| 		// First query: LIMIT 10 (should return 10 rows) | |
| 		result1, err := engine.ExecuteSQL(context.Background(), "SELECT id, user_id, id+user_id FROM user_events LIMIT 10") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error for first query, got %v", err) | |
| 		} | |
| 		if result1.Error != nil { | |
| 			t.Fatalf("Expected no query error for first query, got %v", result1.Error) | |
| 		} | |
| 
 | |
| 		// Second query: LIMIT 10 OFFSET 5 (should return 10 rows, not 5) | |
| 		result2, err := engine.ExecuteSQL(context.Background(), "SELECT id, user_id, id+user_id FROM user_events LIMIT 10 OFFSET 5") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error for second query, got %v", err) | |
| 		} | |
| 		if result2.Error != nil { | |
| 			t.Fatalf("Expected no query error for second query, got %v", result2.Error) | |
| 		} | |
| 
 | |
| 		// Verify column structure is correct | |
| 		expectedColumns := []string{"id", "user_id", "id+user_id"} | |
| 		if len(result2.Columns) != len(expectedColumns) { | |
| 			t.Errorf("Expected %d columns, got %d", len(expectedColumns), len(result2.Columns)) | |
| 		} | |
| 
 | |
| 		// The key assertion: LIMIT 10 OFFSET 5 should return 10 rows (if available) | |
| 		// This was the specific bug reported by the user | |
| 		rows1 := len(result1.Rows) | |
| 		rows2 := len(result2.Rows) | |
| 
 | |
| 		t.Logf("LIMIT 10: returned %d rows", rows1) | |
| 		t.Logf("LIMIT 10 OFFSET 5: returned %d rows", rows2) | |
| 
 | |
| 		if rows1 >= 15 { // If we have enough data for the test to be meaningful | |
| 			if rows2 != 10 { | |
| 				t.Errorf("LIMIT 10 OFFSET 5 should return 10 rows when sufficient data available, got %d", rows2) | |
| 			} | |
| 		} else { | |
| 			t.Logf("Insufficient data (%d rows) to fully test LIMIT 10 OFFSET 5 scenario", rows1) | |
| 		} | |
| 
 | |
| 		// Verify multiplication expressions work in the second query | |
| 		if len(result2.Rows) > 0 { | |
| 			for i, row := range result2.Rows { | |
| 				if len(row) >= 3 { // Check if we have the id+user_id column | |
| 					idVal := row[0].ToString()     // id column | |
| 					userIdVal := row[1].ToString() // user_id column | |
| 					sumVal := row[2].ToString()    // id+user_id column | |
| 					t.Logf("Row %d: id=%s, user_id=%s, id+user_id=%s", i, idVal, userIdVal, sumVal) | |
| 				} | |
| 			} | |
| 		} | |
| 	}) | |
| 
 | |
| 	// Test multiplication specifically | |
| 	t.Run("Multiplication expressions", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT id, id*2 FROM user_events LIMIT 3") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error for multiplication test, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error for multiplication test, got %v", result.Error) | |
| 		} | |
| 
 | |
| 		if len(result.Columns) != 2 { | |
| 			t.Errorf("Expected 2 columns for multiplication test, got %d", len(result.Columns)) | |
| 		} | |
| 
 | |
| 		if len(result.Rows) == 0 { | |
| 			t.Error("Expected some rows for multiplication test") | |
| 		} | |
| 
 | |
| 		// Check that id*2 column has values (not empty) | |
| 		for i, row := range result.Rows { | |
| 			if len(row) >= 2 { | |
| 				idVal := row[0].ToString() | |
| 				doubledVal := row[1].ToString() | |
| 				if doubledVal == "" || doubledVal == "0" { | |
| 					t.Errorf("Row %d: id*2 should not be empty, id=%s, id*2=%s", i, idVal, doubledVal) | |
| 				} else { | |
| 					t.Logf("Row %d: id=%s, id*2=%s ✓", i, idVal, doubledVal) | |
| 				} | |
| 			} | |
| 		} | |
| 	}) | |
| } | |
| 
 | |
| // TestSQLEngine_OFFSET_WithAggregation tests OFFSET with aggregation queries | |
| func TestSQLEngine_OFFSET_WithAggregation(t *testing.T) { | |
| 	engine := NewTestSQLEngine() | |
| 
 | |
| 	// Note: Aggregation queries typically return single rows, so OFFSET behavior is different | |
| 	t.Run("COUNT with OFFSET", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT COUNT(*) FROM user_events LIMIT 1 OFFSET 0") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 		// COUNT typically returns 1 row, so OFFSET 0 should return that row | |
| 		if len(result.Rows) != 1 { | |
| 			t.Errorf("Expected 1 row for COUNT with OFFSET 0, got %d", len(result.Rows)) | |
| 		} | |
| 	}) | |
| 
 | |
| 	t.Run("COUNT with OFFSET 1", func(t *testing.T) { | |
| 		result, err := engine.ExecuteSQL(context.Background(), "SELECT COUNT(*) FROM user_events LIMIT 1 OFFSET 1") | |
| 		if err != nil { | |
| 			t.Fatalf("Expected no error, got %v", err) | |
| 		} | |
| 		if result.Error != nil { | |
| 			t.Fatalf("Expected no query error, got %v", result.Error) | |
| 		} | |
| 		// COUNT returns 1 row, so OFFSET 1 should return 0 rows | |
| 		if len(result.Rows) != 0 { | |
| 			t.Errorf("Expected 0 rows for COUNT with OFFSET 1, got %d", len(result.Rows)) | |
| 		} | |
| 	}) | |
| }
 |