filesql

ExampleDumpDatabase demonstrates exporting modified data

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

// createTempTestData creates temporary CSV files for the example
func createTempTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_example")
	if err != nil {
		log.Fatal(err)
	}

	employeesData := `id,name,department_id,salary,hire_date
1,Alice Johnson,1,95000,2020-01-15
2,Bob Smith,1,85000,2019-03-22
3,Charlie Brown,1,80000,2021-06-10
4,David Wilson,1,75000,2022-02-28
5,Eve Davis,2,70000,2020-09-15
6,Frank Miller,2,65000,2021-11-30
7,Grace Lee,3,60000,2019-12-05
8,Henry Taylor,3,55000,2022-04-18`

	err = os.WriteFile(filepath.Join(tmpDir, "employees.csv"), []byte(employeesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	departmentsData := `id,name,budget,manager_id
1,Engineering,1000000,1
2,Marketing,800000,5
3,Sales,600000,7
4,HR,400000,9`

	err = os.WriteFile(filepath.Join(tmpDir, "departments.csv"), []byte(departmentsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

func main() {
	tmpDir := createTempTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	db, err := filesql.OpenContext(ctx, filepath.Join(tmpDir, "employees.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Modify data in memory
	_, err = db.ExecContext(ctx, `
		UPDATE employees 
		SET salary = salary * 1.10 
		WHERE department_id = 1
	`)
	if err != nil {
		log.Fatal(err)
	}

	// Add a new employee
	_, err = db.ExecContext(ctx, `
		INSERT INTO employees (id, name, department_id, salary, hire_date) 
		VALUES (99, 'New Employee', 2, 60000, '2024-01-01')
	`)
	if err != nil {
		log.Fatal(err)
	}

	// Create output directory
	outputDir := filepath.Join(tmpDir, "output")
	err = os.MkdirAll(outputDir, 0750)
	if err != nil {
		log.Fatal(err)
	}

	// Export modified data
	err = filesql.DumpDatabase(db, outputDir)
	if err != nil {
		log.Fatal(err)
	}

	// Verify export by reading the exported file
	exportedFile := filepath.Join(outputDir, "employees.csv")
	if _, err := os.Stat(exportedFile); err != nil {
		log.Fatal("Exported file not found:", err)
	}

	// Count records in exported file
	db2, err := filesql.OpenContext(ctx, exportedFile)
	if err != nil {
		log.Fatal(err)
	}
	defer db2.Close()

	var count int
	err = db2.QueryRowContext(ctx, "SELECT COUNT(*) FROM employees").Scan(&count)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("Original file: 8 employees\n")
	fmt.Printf("Modified and exported: %d employees\n", count)

	// Extract just the filename for consistent output (normalize path separators for cross-platform compatibility)
	exportPath := strings.Replace(exportedFile, tmpDir, "/tmp/filesql_example*", 1)
	exportPath = strings.ReplaceAll(exportPath, "\\", "/") // Convert Windows backslashes to forward slashes
	fmt.Printf("Export location: %s\n", exportPath)

}

Output:

Original file: 8 employees
Modified and exported: 9 employees
Export location: /tmp/filesql_example*/output/employees.csv

package main

import (
	"fmt"
	"log"
	"os"
	"path/filepath"

	"github.com/nao1215/filesql"
)

func main() {
	tempDir := filepath.Join(os.TempDir(), "filesql_processing_example")
	if err := os.MkdirAll(tempDir, 0750); err != nil {
		log.Fatal(err)
	}
	defer os.RemoveAll(tempDir)

	// Open CSV file
	db, err := filesql.Open(filepath.Join("testdata", "sample.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Process data with SQL
	_, err = db.Exec(`
		UPDATE sample 
		SET age = age + 1 
		WHERE name LIKE '%John%'
	`)
	if err != nil {
		log.Fatal(err)
	}

	// Add aggregated data
	_, err = db.Exec(`
		INSERT INTO sample (id, name, age, email) 
		SELECT 999, 'Summary: ' || COUNT(*), AVG(age), 'summary@example.com'
		FROM sample 
		WHERE id < 999
	`)
	if err != nil {
		log.Fatal(err)
	}

	// Export processed data in different formats for different use cases

	// 1. TSV for spreadsheet import
	options := filesql.NewDumpOptions().WithFormat(filesql.OutputFormatTSV)
	spreadsheetDir := filepath.Join(tempDir, "for_spreadsheet")
	if err := filesql.DumpDatabase(db, spreadsheetDir, options); err != nil {
		log.Fatal(err)
	}
	fmt.Println("Exported TSV for spreadsheet import")

	// 2. Compressed CSV for archival
	options = filesql.NewDumpOptions().
		WithFormat(filesql.OutputFormatCSV).
		WithCompression(filesql.CompressionGZ)
	archiveDir := filepath.Join(tempDir, "for_archive")
	if err := filesql.DumpDatabase(db, archiveDir, options); err != nil {
		log.Fatal(err)
	}
	fmt.Println("Exported compressed CSV for archival")

	// 3. LTSV for log analysis
	options = filesql.NewDumpOptions().WithFormat(filesql.OutputFormatLTSV)
	logDir := filepath.Join(tempDir, "for_logs")
	if err := filesql.DumpDatabase(db, logDir, options); err != nil {
		log.Fatal(err)
	}
	fmt.Println("Exported LTSV for log analysis")

	// Show what was created
	dirs := []string{"for_spreadsheet", "for_archive", "for_logs"}
	for _, dir := range dirs {
		files, err := filepath.Glob(filepath.Join(tempDir, dir, "*"))
		if err != nil {
			log.Fatal(err)
		}
		for _, file := range files {
			fmt.Printf("%s: %s\n", dir, filepath.Base(file))
		}
	}

}

Output:

Exported TSV for spreadsheet import
Exported compressed CSV for archival
Exported LTSV for log analysis
for_spreadsheet: sample.tsv
for_archive: sample.csv.gz
for_logs: sample.ltsv

package main

import (
	"fmt"
	"log"
	"os"
	"path/filepath"

	"github.com/nao1215/filesql"
)

func main() {
	tempDir := filepath.Join(os.TempDir(), "filesql_formats_example")
	if err := os.MkdirAll(tempDir, 0750); err != nil {
		log.Fatal(err)
	}
	defer os.RemoveAll(tempDir)

	// Open CSV file and modify data
	db, err := filesql.Open(filepath.Join("testdata", "sample.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Add some data to demonstrate functionality
	_, err = db.Exec("INSERT INTO sample (id, name, age, email) VALUES (4, 'Alice Brown', 28, 'alice@example.com')")
	if err != nil {
		log.Fatal(err)
	}

	// Demonstrate different compression options
	compressionTypes := []struct {
		name        string
		compression filesql.CompressionType
		extension   string
	}{
		{"No compression", filesql.CompressionNone, ""},
		{"Gzip compression", filesql.CompressionGZ, ".gz"},
		{"XZ compression", filesql.CompressionXZ, ".xz"},
		{"Zstd compression", filesql.CompressionZSTD, ".zst"},
	}

	for _, ct := range compressionTypes {
		fmt.Printf("%s:\n", ct.name)

		options := filesql.NewDumpOptions().
			WithFormat(filesql.OutputFormatCSV).
			WithCompression(ct.compression)

		outputDir := filepath.Join(tempDir, "compression_"+ct.compression.String())
		if err := filesql.DumpDatabase(db, outputDir, options); err != nil {
			log.Fatal(err)
		}

		files, err := filepath.Glob(filepath.Join(outputDir, "*"))
		if err != nil {
			log.Fatal(err)
		}
		for _, file := range files {
			fmt.Printf("  %s\n", filepath.Base(file))
		}
	}

}

Output:

No compression:
  sample.csv
Gzip compression:
  sample.csv.gz
XZ compression:
  sample.csv.xz
Zstd compression:
  sample.csv.zst

package main

import (
	"fmt"
	"log"
	"os"
	"path/filepath"

	"github.com/nao1215/filesql"
)

func main() {
	// Create a temporary directory for output
	tempDir := filepath.Join(os.TempDir(), "filesql_dump_example")
	if err := os.MkdirAll(tempDir, 0750); err != nil {
		log.Fatal(err)
	}
	defer os.RemoveAll(tempDir)

	// Open CSV file
	db, err := filesql.Open(filepath.Join("testdata", "sample.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Example 1: Default CSV output (no options)
	fmt.Println("Example 1: Default CSV output")
	csvDir := filepath.Join(tempDir, "csv_output")
	if err := filesql.DumpDatabase(db, csvDir); err != nil {
		log.Fatal(err)
	}

	// List output files
	files1, err := filepath.Glob(filepath.Join(csvDir, "*"))
	if err != nil {
		log.Fatal(err)
	}
	for _, file := range files1 {
		fmt.Printf("Created: %s\n", filepath.Base(file))
	}

	// Example 2: TSV output with gzip compression
	fmt.Println("\nExample 2: TSV output with gzip compression")
	tsvDir := filepath.Join(tempDir, "tsv_output")
	options := filesql.NewDumpOptions().
		WithFormat(filesql.OutputFormatTSV).
		WithCompression(filesql.CompressionGZ)
	if err := filesql.DumpDatabase(db, tsvDir, options); err != nil {
		log.Fatal(err)
	}

	files2, err := filepath.Glob(filepath.Join(tsvDir, "*"))
	if err != nil {
		log.Fatal(err)
	}
	for _, file := range files2 {
		fmt.Printf("Created: %s\n", filepath.Base(file))
	}

	// Example 3: LTSV output with zstd compression
	fmt.Println("\nExample 3: LTSV output with zstd compression")
	ltsvDir := filepath.Join(tempDir, "ltsv_output")
	options3 := filesql.NewDumpOptions().
		WithFormat(filesql.OutputFormatLTSV).
		WithCompression(filesql.CompressionZSTD)
	if err := filesql.DumpDatabase(db, ltsvDir, options3); err != nil {
		log.Fatal(err)
	}

	files3, err := filepath.Glob(filepath.Join(ltsvDir, "*"))
	if err != nil {
		log.Fatal(err)
	}
	for _, file := range files3 {
		fmt.Printf("Created: %s\n", filepath.Base(file))
	}

}

Output:

Example 1: Default CSV output
Created: sample.csv

Example 2: TSV output with gzip compression
Created: sample.tsv.gz

Example 3: LTSV output with zstd compression
Created: sample.ltsv.zst

ExampleOpen demonstrates how to use filesql.Open() with complex SQL queries. This example shows advanced SQL features including JOINs, window functions, subqueries, and aggregations on CSV data loaded into an in-memory SQLite database.

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"

	"github.com/nao1215/filesql"
)

func main() {
	// Create temporary test data files
	tmpDir := createTempTestData()
	defer os.RemoveAll(tmpDir)

	// Open the database with multiple files
	db, err := filesql.Open(filepath.Join(tmpDir, "employees.csv"), filepath.Join(tmpDir, "departments.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Complex query demonstrating multiple SQL features:
	// - JOINs between tables
	// - Window functions (RANK, AVG, COUNT)
	// - Subqueries with correlated conditions
	// - CASE statements
	// - Grouping and ordering
	query := `
		SELECT 
			e.name,
			d.name as department_name,
			e.salary,
			d.budget,
			RANK() OVER (PARTITION BY e.department_id ORDER BY e.salary DESC) as salary_rank_in_dept,
			AVG(e.salary) OVER (PARTITION BY e.department_id) as dept_avg_salary,
			COUNT(*) OVER (PARTITION BY e.department_id) as dept_employee_count,
			CASE 
				WHEN e.salary > (SELECT AVG(salary) FROM employees WHERE department_id = e.department_id) * 1.2
				THEN 'High Performer'
				WHEN e.salary < (SELECT AVG(salary) FROM employees WHERE department_id = e.department_id) * 0.8  
				THEN 'Below Average'
				ELSE 'Average'
			END as performance_category,
			ROUND(e.salary / d.budget * 100, 2) as salary_budget_percentage
		FROM employees e
		JOIN departments d ON e.department_id = d.id
		WHERE e.salary > (
			SELECT AVG(salary) * 0.7
			FROM employees e2 
			WHERE e2.department_id = e.department_id
		)
		AND d.budget > 500000
		ORDER BY d.name, e.salary DESC
		LIMIT 10
	`

	rows, err := db.QueryContext(context.Background(), query)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	fmt.Println("Employee Analysis Report:")
	fmt.Println("========================")

	for rows.Next() {
		var name, deptName, perfCategory string
		var salary, budget, deptAvgSalary, salaryBudgetPct float64
		var salaryRank, deptEmpCount int

		err := rows.Scan(&name, &deptName, &salary, &budget, &salaryRank,
			&deptAvgSalary, &deptEmpCount, &perfCategory, &salaryBudgetPct)
		if err != nil {
			log.Fatal(err)
		}

		fmt.Printf("%-15s | %-12s | $%7.0f | Rank: %d/%d | %s\n",
			name, deptName, salary, salaryRank, deptEmpCount, perfCategory)
	}

	if err = rows.Err(); err != nil {
		log.Fatal(err)
	}

}

// createTempTestData creates temporary CSV files for the example
func createTempTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_example")
	if err != nil {
		log.Fatal(err)
	}

	employeesData := `id,name,department_id,salary,hire_date
1,Alice Johnson,1,95000,2020-01-15
2,Bob Smith,1,85000,2019-03-22
3,Charlie Brown,1,80000,2021-06-10
4,David Wilson,1,75000,2022-02-28
5,Eve Davis,2,70000,2020-09-15
6,Frank Miller,2,65000,2021-11-30
7,Grace Lee,3,60000,2019-12-05
8,Henry Taylor,3,55000,2022-04-18`

	err = os.WriteFile(filepath.Join(tmpDir, "employees.csv"), []byte(employeesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	departmentsData := `id,name,budget,manager_id
1,Engineering,1000000,1
2,Marketing,800000,5
3,Sales,600000,7
4,HR,400000,9`

	err = os.WriteFile(filepath.Join(tmpDir, "departments.csv"), []byte(departmentsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

Output:

Employee Analysis Report:
========================
Alice Johnson   | Engineering  | $  95000 | Rank: 1/4 | Average
Bob Smith       | Engineering  | $  85000 | Rank: 2/4 | Average
Charlie Brown   | Engineering  | $  80000 | Rank: 3/4 | Average
David Wilson    | Engineering  | $  75000 | Rank: 4/4 | Average
Eve Davis       | Marketing    | $  70000 | Rank: 1/2 | Average
Frank Miller    | Marketing    | $  65000 | Rank: 2/2 | Average
Grace Lee       | Sales        | $  60000 | Rank: 1/2 | Average
Henry Taylor    | Sales        | $  55000 | Rank: 2/2 | Average

ExampleOpen_advancedSQL demonstrates advanced SQL features available in SQLite3

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

func main() {
	tmpDir := createAdvancedTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	db, err := filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	fmt.Println("=== Advanced SQL Features ===")

	// Window functions with RANK() and ROW_NUMBER()
	fmt.Println("\n1. Window Functions - Employee Rankings by Department:")
	rows, err := db.QueryContext(ctx, `
		SELECT 
			e.name,
			d.name as department,
			e.salary,
			RANK() OVER (PARTITION BY e.department_id ORDER BY e.salary DESC) as salary_rank,
			ROW_NUMBER() OVER (ORDER BY e.salary DESC) as overall_rank
		FROM employees e
		JOIN departments d ON e.department_id = d.id
		ORDER BY e.department_id, salary_rank
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-15s %-12s %-8s %-10s %s\n", "Name", "Department", "Salary", "Dept Rank", "Overall Rank")
	fmt.Println(strings.Repeat("-", 65))

	for rows.Next() {
		var name, department string
		var salary float64
		var salaryRank, overallRank int

		if err := rows.Scan(&name, &department, &salary, &salaryRank, &overallRank); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-15s %-12s $%-7.0f %-10d %d\n", name, department, salary, salaryRank, overallRank)
	}
	_ = rows.Close() // Ignore close error in test cleanup

	// Common Table Expressions (CTE)
	fmt.Println("\n2. Common Table Expressions - Department Analysis:")
	rows, err = db.QueryContext(ctx, `
		WITH dept_stats AS (
			SELECT 
				d.name as department,
				COUNT(e.id) as employee_count,
				AVG(e.salary) as avg_salary,
				MAX(e.salary) as max_salary,
				MIN(e.salary) as min_salary
			FROM departments d
			LEFT JOIN employees e ON d.id = e.department_id
			GROUP BY d.id, d.name
		),
		company_avg AS (
			SELECT AVG(salary) as company_avg_salary
			FROM employees
		)
		SELECT 
			ds.department,
			ds.employee_count,
			ds.avg_salary,
			ca.company_avg_salary,
			ds.avg_salary - ca.company_avg_salary as salary_diff,
			CASE 
				WHEN ds.avg_salary > ca.company_avg_salary THEN 'Above Average'
				WHEN ds.avg_salary < ca.company_avg_salary THEN 'Below Average'
				ELSE 'At Average'
			END as comparison
		FROM dept_stats ds
		CROSS JOIN company_avg ca
		WHERE ds.employee_count > 0
		ORDER BY ds.avg_salary DESC
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-12s %-5s %-10s %-12s %-10s %s\n", "Department", "Count", "Avg Salary", "Company Avg", "Difference", "Comparison")
	fmt.Println(strings.Repeat("-", 75))

	for rows.Next() {
		var department, comparison string
		var employeeCount int
		var avgSalary, companyAvg, salaryDiff float64

		if err := rows.Scan(&department, &employeeCount, &avgSalary, &companyAvg, &salaryDiff, &comparison); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-12s %-5d $%-9.0f $%-11.0f $%-9.0f %s\n",
			department, employeeCount, avgSalary, companyAvg, salaryDiff, comparison)
	}
	_ = rows.Close() // Ignore close error in test cleanup

	// JSON operations (if data contains JSON)
	fmt.Println("\n3. Text Functions - Name Analysis:")
	rows, err = db.QueryContext(ctx, `
		SELECT 
			name,
			LENGTH(name) as name_length,
			UPPER(SUBSTR(name, 1, 1)) || LOWER(SUBSTR(name, 2)) as formatted_name,
			INSTR(name, ' ') as space_position,
			CASE 
				WHEN INSTR(name, ' ') > 0 THEN SUBSTR(name, 1, INSTR(name, ' ') - 1)
				ELSE name
			END as first_name
		FROM employees
		WHERE LENGTH(name) > 8
		ORDER BY name_length DESC
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-15s %-6s %-15s %-8s %s\n", "Name", "Length", "Formatted", "Space@", "First Name")
	fmt.Println(strings.Repeat("-", 60))

	for rows.Next() {
		var name, formattedName, firstName string
		var nameLength, spacePos int

		if err := rows.Scan(&name, &nameLength, &formattedName, &spacePos, &firstName); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-15s %-6d %-15s %-8d %s\n", name, nameLength, formattedName, spacePos, firstName)
	}
	_ = rows.Close() // Ignore close error in test cleanup

}

// createAdvancedTestData creates test data for advanced SQL examples
func createAdvancedTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_advanced_example_*")
	if err != nil {
		log.Fatal(err)
	}

	employeesData := `id,name,department_id,salary,hire_date
1,Alice Johnson,1,95000,2023-01-15
2,Bob Smith,2,85000,2023-02-20
3,Charlie Brown,1,80000,2023-03-10
4,David Wilson,1,75000,2023-04-05
5,Eve Davis,2,65000,2023-05-15
6,Frank Miller,3,70000,2023-06-01`

	employeesFile := filepath.Join(tmpDir, "employees.csv")
	err = os.WriteFile(employeesFile, []byte(employeesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	departmentsData := `id,name,budget
1,Engineering,500000
2,Sales,300000
3,Marketing,200000
4,HR,150000`

	departmentsFile := filepath.Join(tmpDir, "departments.csv")
	err = os.WriteFile(departmentsFile, []byte(departmentsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

Output:

=== Advanced SQL Features ===

1. Window Functions - Employee Rankings by Department:
Name            Department   Salary   Dept Rank  Overall Rank
-----------------------------------------------------------------
Alice Johnson   Engineering  $95000   1          1
Charlie Brown   Engineering  $80000   2          3
David Wilson    Engineering  $75000   3          4
Bob Smith       Sales        $85000   1          2
Eve Davis       Sales        $65000   2          6
Frank Miller    Marketing    $70000   1          5

2. Common Table Expressions - Department Analysis:
Department   Count Avg Salary Company Avg  Difference Comparison
---------------------------------------------------------------------------
Engineering  3     $83333     $78333       $5000      Above Average
Sales        2     $75000     $78333       $-3333     Below Average
Marketing    1     $70000     $78333       $-8333     Below Average

3. Text Functions - Name Analysis:
Name            Length Formatted       Space@   First Name
------------------------------------------------------------
Alice Johnson   13     Alice johnson   6        Alice
Charlie Brown   13     Charlie brown   8        Charlie
David Wilson    12     David wilson    6        David
Frank Miller    12     Frank miller    6        Frank
Bob Smith       9      Bob smith       4        Bob
Eve Davis       9      Eve davis       4        Eve

ExampleOpen_compressionSupport demonstrates working with compressed files

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

func main() {
	tmpDir := createCompressedTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	// Open compressed files seamlessly
	db, err := filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	fmt.Println("=== Compression Support Demo ===")
	fmt.Println("Successfully loaded compressed files:")

	// List all tables from compressed files
	rows, err := db.QueryContext(ctx, `
		SELECT name, sql 
		FROM sqlite_master 
		WHERE type='table' 
		ORDER BY name
	`)
	if err != nil {
		log.Fatal(err)
	}

	for rows.Next() {
		var tableName, createSQL string
		if err := rows.Scan(&tableName, &createSQL); err != nil {
			log.Fatal(err)
		}

		// Count records in each table
		var count int
		countQuery := "SELECT COUNT(*) FROM " + tableName
		if err := db.QueryRowContext(ctx, countQuery).Scan(&count); err != nil {
			log.Fatal(err)
		}

		fmt.Printf("- %s: %d records\n", tableName, count)
	}
	_ = rows.Close() // Ignore close error in test cleanup

	// Demonstrate querying across compressed files
	fmt.Println("\nCross-file analysis from compressed data:")

	analysisRows, err := db.QueryContext(ctx, `
		SELECT 
			'logs' as source_table,
			COUNT(*) as total_records,
			MIN(timestamp) as earliest,
			MAX(timestamp) as latest
		FROM logs
		
		UNION ALL
		
		SELECT 
			'products' as source_table,
			COUNT(*) as total_records,
			'N/A' as earliest,
			'N/A' as latest
		FROM products
		
		ORDER BY source_table
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-12s %-8s %-19s %s\n", "Table", "Records", "Earliest", "Latest")
	fmt.Println(strings.Repeat("-", 60))

	for analysisRows.Next() {
		var sourceTable, earliest, latest string
		var totalRecords int

		if err := analysisRows.Scan(&sourceTable, &totalRecords, &earliest, &latest); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-12s %-8d %-19s %s\n", sourceTable, totalRecords, earliest, latest)
	}
	_ = analysisRows.Close() // Ignore close error in test cleanup

}

// createCompressedTestData creates test data with compressed files
func createCompressedTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_compressed_example_*")
	if err != nil {
		log.Fatal(err)
	}

	logsData := `timestamp,level,message,user_id
2024-01-01 10:00:00,INFO,User login,1001
2024-01-01 11:30:00,INFO,Order created,1002
2024-01-01 12:15:00,ERROR,Payment failed,1003
2024-01-01 13:45:00,INFO,User logout,1001
2024-01-01 14:00:00,INFO,System backup completed,0`

	logsFile := filepath.Join(tmpDir, "logs.csv")
	err = os.WriteFile(logsFile, []byte(logsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	productsData := `id,name,category,price,in_stock
1,Laptop Pro,Electronics,1299.99,true
2,Office Chair,Furniture,299.99,true
3,Wireless Mouse,Electronics,49.99,false`

	productsFile := filepath.Join(tmpDir, "products.csv")
	err = os.WriteFile(productsFile, []byte(productsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

Output:

=== Compression Support Demo ===
Successfully loaded compressed files:
- logs: 5 records
- products: 3 records

Cross-file analysis from compressed data:
Table        Records  Earliest            Latest
------------------------------------------------------------
logs         5        2024-01-01 10:00:00 2024-01-01 14:00:00
products     3        N/A                 N/A

ExampleOpen_constraints demonstrates the constraint that modifications don't affect original files

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"

	"github.com/nao1215/filesql"
)

// createTempTestData creates temporary CSV files for the example
func createTempTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_example")
	if err != nil {
		log.Fatal(err)
	}

	employeesData := `id,name,department_id,salary,hire_date
1,Alice Johnson,1,95000,2020-01-15
2,Bob Smith,1,85000,2019-03-22
3,Charlie Brown,1,80000,2021-06-10
4,David Wilson,1,75000,2022-02-28
5,Eve Davis,2,70000,2020-09-15
6,Frank Miller,2,65000,2021-11-30
7,Grace Lee,3,60000,2019-12-05
8,Henry Taylor,3,55000,2022-04-18`

	err = os.WriteFile(filepath.Join(tmpDir, "employees.csv"), []byte(employeesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	departmentsData := `id,name,budget,manager_id
1,Engineering,1000000,1
2,Marketing,800000,5
3,Sales,600000,7
4,HR,400000,9`

	err = os.WriteFile(filepath.Join(tmpDir, "departments.csv"), []byte(departmentsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

func main() {
	tmpDir := createTempTestData()
	defer os.RemoveAll(tmpDir)

	db, err := filesql.Open(filepath.Join(tmpDir, "employees.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Show original data count
	var originalCount int
	err = db.QueryRowContext(context.Background(), "SELECT COUNT(*) FROM employees").Scan(&originalCount)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Original employee count: %d\n", originalCount)

	// Insert new data (only affects in-memory database)
	_, err = db.ExecContext(context.Background(), "INSERT INTO employees (id, name, department_id, salary, hire_date) VALUES (99, 'Test User', 1, 50000, '2023-01-01')")
	if err != nil {
		log.Fatal(err)
	}

	// Show in-memory count
	var memoryCount int
	err = db.QueryRowContext(context.Background(), "SELECT COUNT(*) FROM employees").Scan(&memoryCount)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("In-memory count after INSERT: %d\n", memoryCount)

	// Verify original file is unchanged by reopening
	db2, err := filesql.Open(filepath.Join(tmpDir, "employees.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db2.Close()

	var fileCount int
	err = db2.QueryRowContext(context.Background(), "SELECT COUNT(*) FROM employees").Scan(&fileCount)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("File-based count (unchanged): %d\n", fileCount)

}

Output:

Original employee count: 8
In-memory count after INSERT: 9
File-based count (unchanged): 8

ExampleOpen_customerInsights demonstrates customer behavior analysis

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

// createSalesTestData creates test data for sales analysis examples
func createSalesTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_sales_example")
	if err != nil {
		log.Fatal(err)
	}

	salesData := `order_id,customer_id,product_name,category,quantity,unit_price,order_date,region
1,101,Laptop Pro,Electronics,2,1299.99,2024-01-15,North
2,102,Wireless Mouse,Electronics,1,29.99,2024-01-16,South
3,103,Office Chair,Furniture,1,299.99,2024-01-17,East
4,101,USB Cable,Electronics,3,12.99,2024-01-18,North
5,104,Standing Desk,Furniture,1,599.99,2024-01-19,West
6,105,Bluetooth Speaker,Electronics,2,79.99,2024-01-20,South
7,106,Coffee Table,Furniture,1,199.99,2024-01-21,East
8,102,Keyboard,Electronics,1,89.99,2024-01-22,South
9,107,Monitor 24inch,Electronics,1,249.99,2024-01-23,North
10,103,Desk Lamp,Furniture,2,39.99,2024-01-24,East`

	err = os.WriteFile(filepath.Join(tmpDir, "sales.csv"), []byte(salesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	customersData := `customer_id,name,email,city,registration_date
101,John Doe,john@example.com,New York,2023-06-01
102,Jane Smith,jane@example.com,Los Angeles,2023-07-15
103,Bob Johnson,bob@example.com,Chicago,2023-08-20
104,Alice Brown,alice@example.com,Houston,2023-09-10
105,Charlie Wilson,charlie@example.com,Phoenix,2023-10-05
106,Diana Lee,diana@example.com,Philadelphia,2023-11-12
107,Frank Miller,frank@example.com,San Antonio,2023-12-03`

	err = os.WriteFile(filepath.Join(tmpDir, "customers.csv"), []byte(customersData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

func main() {
	tmpDir := createSalesTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	db, err := filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Customer lifetime value and behavior analysis
	query := `
		SELECT 
			c.name,
			c.city,
			COUNT(s.order_id) as total_orders,
			SUM(s.quantity * s.unit_price) as lifetime_value,
			AVG(s.quantity * s.unit_price) as avg_order_value,
			MIN(s.order_date) as first_purchase,
			MAX(s.order_date) as last_purchase,
			julianday(MAX(s.order_date)) - julianday(MIN(s.order_date)) as days_active,
			COUNT(DISTINCT s.category) as categories_purchased
		FROM customers c
		JOIN sales s ON c.customer_id = s.customer_id
		GROUP BY c.customer_id, c.name, c.city
		HAVING total_orders > 1
		ORDER BY lifetime_value DESC
	`

	rows, err := db.QueryContext(ctx, query)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	fmt.Println("Customer Insights (Multi-Purchase Customers):")
	fmt.Println("===========================================")
	fmt.Printf("%-12s %-12s %-7s %-10s %-10s %-12s %-12s %-6s %s\n",
		"Name", "City", "Orders", "LTV", "Avg Order", "First Buy", "Last Buy", "Days", "Categories")
	fmt.Println(strings.Repeat("-", 100))

	for rows.Next() {
		var name, city, firstPurchase, lastPurchase string
		var totalOrders, daysActive, categoriesPurchased int
		var lifetimeValue, avgOrderValue float64

		err := rows.Scan(&name, &city, &totalOrders, &lifetimeValue, &avgOrderValue,
			&firstPurchase, &lastPurchase, &daysActive, &categoriesPurchased)
		if err != nil {
			log.Fatal(err)
		}

		fmt.Printf("%-12s %-12s %-7d $%-9.2f $%-9.2f %-12s %-12s %-6d %d\n",
			name, city, totalOrders, lifetimeValue, avgOrderValue,
			firstPurchase, lastPurchase, daysActive, categoriesPurchased)
	}

}

Output:

Customer Insights (Multi-Purchase Customers):
===========================================
Name         City         Orders  LTV        Avg Order  First Buy    Last Buy     Days   Categories
----------------------------------------------------------------------------------------------------
John Doe     New York     2       $2638.95   $1319.47   2024-01-15   2024-01-18   3      1
Bob Johnson  Chicago      2       $379.97    $189.99    2024-01-17   2024-01-24   7      1
Jane Smith   Los Angeles  2       $119.98    $59.99     2024-01-16   2024-01-22   6      1

ExampleOpen_errorHandling demonstrates proper error handling patterns

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

// createTempTestData creates temporary CSV files for the example
func createTempTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_example")
	if err != nil {
		log.Fatal(err)
	}

	employeesData := `id,name,department_id,salary,hire_date
1,Alice Johnson,1,95000,2020-01-15
2,Bob Smith,1,85000,2019-03-22
3,Charlie Brown,1,80000,2021-06-10
4,David Wilson,1,75000,2022-02-28
5,Eve Davis,2,70000,2020-09-15
6,Frank Miller,2,65000,2021-11-30
7,Grace Lee,3,60000,2019-12-05
8,Henry Taylor,3,55000,2022-04-18`

	err = os.WriteFile(filepath.Join(tmpDir, "employees.csv"), []byte(employeesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	departmentsData := `id,name,budget,manager_id
1,Engineering,1000000,1
2,Marketing,800000,5
3,Sales,600000,7
4,HR,400000,9`

	err = os.WriteFile(filepath.Join(tmpDir, "departments.csv"), []byte(departmentsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

func main() {
	// Example 1: Handling non-existent files gracefully
	_, err := filesql.Open("nonexistent.csv")
	if err != nil {
		fmt.Printf("Expected error for non-existent file: %v\n", err)
	}

	// Example 2: Context timeout handling
	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Nanosecond) // Very short timeout
	defer cancel()

	// This will likely timeout
	tmpDir := createTempTestData()
	defer os.RemoveAll(tmpDir)

	time.Sleep(10 * time.Millisecond) // Ensure timeout triggers
	_, err = filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		// Extract the core error message (context deadline exceeded)
		errMsg := err.Error()
		if strings.Contains(errMsg, "context deadline exceeded") {
			fmt.Printf("Expected timeout error: %s\n", "context deadline exceeded")
		} else {
			fmt.Printf("Expected timeout error: %v\n", err)
		}
	}

	// Example 3: Successful operation with proper error checking
	ctx2, cancel2 := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel2()

	db, err := filesql.OpenContext(ctx2, tmpDir)
	if err != nil {
		fmt.Printf("Unexpected error: %v\n", err)
		return
	}
	defer db.Close()

	// Test query with error handling
	rows, err := db.QueryContext(ctx2, "SELECT COUNT(*) FROM employees")
	if err != nil {
		fmt.Printf("Query error: %v\n", err)
		return
	}
	defer rows.Close()

	var count int
	if rows.Next() {
		if err := rows.Scan(&count); err != nil {
			fmt.Printf("Scan error: %v\n", err)
			return
		}
		fmt.Printf("Successfully counted %d employees\n", count)
	}

	if err := rows.Err(); err != nil {
		fmt.Printf("Rows iteration error: %v\n", err)
		return
	}

}

Output:

Expected error for non-existent file: failed to load file: path does not exist: nonexistent.csv
Expected timeout error: context deadline exceeded
Successfully counted 8 employees

ExampleOpen_financialDataAnalysis demonstrates financial data processing

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

func main() {
	tmpDir := createFinancialTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	db, err := filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	fmt.Println("=== Financial Data Analysis ===")

	// Monthly revenue trend
	fmt.Println("\n1. Monthly Revenue Trend:")
	rows, err := db.QueryContext(ctx, `
		SELECT 
			strftime('%Y-%m', transaction_date) as month,
			COUNT(*) as transaction_count,
			SUM(amount) as total_revenue,
			AVG(amount) as avg_transaction,
			MAX(amount) as largest_transaction
		FROM transactions 
		WHERE type = 'sale'
		GROUP BY month
		ORDER BY month
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-8s %-6s %-10s %-8s %s\n", "Month", "Count", "Revenue", "Average", "Largest")
	fmt.Println(strings.Repeat("-", 50))
	for rows.Next() {
		var month string
		var count int
		var revenue, average, largest float64
		if err := rows.Scan(&month, &count, &revenue, &average, &largest); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-8s %-6d $%-9.2f $%-7.2f $%.2f\n", month, count, revenue, average, largest)
	}
	_ = rows.Close() // Ignore close error in test cleanup

	// Expense category breakdown
	fmt.Println("\n2. Expense Categories:")
	rows, err = db.QueryContext(ctx, `
		SELECT 
			category,
			COUNT(*) as transaction_count,
			SUM(ABS(amount)) as total_expense,
			ROUND(SUM(ABS(amount)) * 100.0 / (
				SELECT SUM(ABS(amount)) FROM transactions WHERE type = 'expense'
			), 2) as percentage
		FROM transactions 
		WHERE type = 'expense'
		GROUP BY category
		ORDER BY total_expense DESC
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-15s %-6s %-12s %-10s\n", "Category", "Count", "Total", "Percentage")
	fmt.Println(strings.Repeat("-", 45))
	for rows.Next() {
		var category string
		var count int
		var expense, percentage float64
		if err := rows.Scan(&category, &count, &expense, &percentage); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-15s %-6d $%-11.2f %-10.2f%%\n", category, count, expense, percentage)
	}
	_ = rows.Close() // Ignore close error in test cleanup

	// Cash flow summary
	fmt.Println("\n3. Cash Flow Summary:")
	var totalIncome, totalExpenses, netIncome float64
	err = db.QueryRowContext(ctx, `
		SELECT 
			SUM(CASE WHEN type = 'sale' THEN amount ELSE 0 END) as total_income,
			SUM(CASE WHEN type = 'expense' THEN ABS(amount) ELSE 0 END) as total_expenses,
			SUM(CASE WHEN type = 'sale' THEN amount ELSE -ABS(amount) END) as net_income
		FROM transactions
	`).Scan(&totalIncome, &totalExpenses, &netIncome)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("Total Income:  $%.2f\n", totalIncome)
	fmt.Printf("Total Expenses: $%.2f\n", totalExpenses)
	fmt.Printf("Net Income:    $%.2f\n", netIncome)
	fmt.Printf("Profit Margin: %.2f%%\n", (netIncome/totalIncome)*100)

}

// createFinancialTestData creates test data for financial analysis examples
func createFinancialTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_financial_example_*")
	if err != nil {
		log.Fatal(err)
	}

	transactionData := `transaction_id,transaction_date,type,category,amount,description
1,2024-01-15,sale,Product Sales,1500.00,Sale of premium product
2,2024-01-20,sale,Product Sales,850.00,Sale of standard product
3,2024-01-25,sale,Service,1200.00,Consulting service
4,2024-01-10,expense,Office Supplies,-150.00,Office equipment purchase
5,2024-01-18,expense,Marketing,-250.00,Social media advertising
6,2024-02-05,sale,Product Sales,1200.00,Sale of premium product
7,2024-02-15,sale,Service,1000.00,Training service
8,2024-02-08,expense,Office Supplies,-200.00,Stationery purchase`

	transactionFile := filepath.Join(tmpDir, "transactions.csv")
	err = os.WriteFile(transactionFile, []byte(transactionData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

Output:

=== Financial Data Analysis ===

1. Monthly Revenue Trend:
Month    Count  Revenue    Average  Largest
--------------------------------------------------
2024-01  3      $3550.00   $1183.33 $1500.00
2024-02  2      $2200.00   $1100.00 $1200.00

2. Expense Categories:
Category        Count  Total        Percentage
---------------------------------------------
Office Supplies 2      $350.00      58.33     %
Marketing       1      $250.00      41.67     %

3. Cash Flow Summary:
Total Income:  $5750.00
Total Expenses: $600.00
Net Income:    $5150.00
Profit Margin: 89.57%

ExampleOpen_multipleFiles demonstrates opening multiple files and directories

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"

	"github.com/nao1215/filesql"
)

// createTempTestData creates temporary CSV files for the example
func createTempTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_example")
	if err != nil {
		log.Fatal(err)
	}

	employeesData := `id,name,department_id,salary,hire_date
1,Alice Johnson,1,95000,2020-01-15
2,Bob Smith,1,85000,2019-03-22
3,Charlie Brown,1,80000,2021-06-10
4,David Wilson,1,75000,2022-02-28
5,Eve Davis,2,70000,2020-09-15
6,Frank Miller,2,65000,2021-11-30
7,Grace Lee,3,60000,2019-12-05
8,Henry Taylor,3,55000,2022-04-18`

	err = os.WriteFile(filepath.Join(tmpDir, "employees.csv"), []byte(employeesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	departmentsData := `id,name,budget,manager_id
1,Engineering,1000000,1
2,Marketing,800000,5
3,Sales,600000,7
4,HR,400000,9`

	err = os.WriteFile(filepath.Join(tmpDir, "departments.csv"), []byte(departmentsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

func main() {
	tmpDir := createTempTestData()
	defer os.RemoveAll(tmpDir)

	// Open database with multiple paths (files and directories)
	db, err := filesql.Open(tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Query to show all available tables
	rows, err := db.QueryContext(context.Background(), "SELECT name FROM sqlite_master WHERE type='table' ORDER BY name")
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	fmt.Println("Available tables:")
	for rows.Next() {
		var tableName string
		if err := rows.Scan(&tableName); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("- %s\n", tableName)
	}

}

Output:

Available tables:
- departments
- employees

ExampleOpen_performanceOptimization demonstrates techniques for handling large datasets efficiently

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"time"

	"github.com/nao1215/filesql"
)

func main() {
	tmpDir := createLargeTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	db, err := filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Technique 1: Use LIMIT and OFFSET for pagination
	fmt.Println("=== Performance Optimization Techniques ===")
	fmt.Println("\n1. Pagination with LIMIT and OFFSET:")

	pageSize := 3
	offset := 0

	for page := 1; page <= 2; page++ {
		rows, err := db.QueryContext(ctx, `
			SELECT customer_id, name, total_orders 
			FROM customer_summary 
			ORDER BY total_orders DESC 
			LIMIT ? OFFSET ?
		`, pageSize, offset)
		if err != nil {
			log.Fatal(err)
		}

		fmt.Printf("Page %d:\n", page)
		for rows.Next() {
			var customerID int
			var name string
			var totalOrders int
			if err := rows.Scan(&customerID, &name, &totalOrders); err != nil {
				log.Fatal(err)
			}
			fmt.Printf("  - %s (ID: %d, Orders: %d)\n", name, customerID, totalOrders)
		}
		_ = rows.Close() // Ignore close error in test cleanup
		offset += pageSize
	}

	// Technique 2: Use indexes by querying with WHERE clauses on sorted columns
	fmt.Println("\n2. Efficient filtering with indexes:")
	rows, err := db.QueryContext(ctx, `
		SELECT name, email, registration_date 
		FROM customer_summary 
		WHERE total_spent > 1000 
		ORDER BY total_spent DESC
	`)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	fmt.Println("High-value customers:")
	for rows.Next() {
		var name, email, regDate string
		if err := rows.Scan(&name, &email, &regDate); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("  - %s (%s) - Registered: %s\n", name, email, regDate)
	}

	// Technique 3: Aggregate queries for summary statistics
	fmt.Println("\n3. Summary statistics:")
	var totalCustomers int
	var avgOrders, totalRevenue, avgSpent float64

	err = db.QueryRowContext(ctx, `
		SELECT 
			COUNT(*) as total_customers,
			AVG(total_orders) as avg_orders,
			SUM(total_spent) as total_revenue,
			AVG(total_spent) as avg_spent
		FROM customer_summary
	`).Scan(&totalCustomers, &avgOrders, &totalRevenue, &avgSpent)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("Total customers: %d\n", totalCustomers)
	fmt.Printf("Average orders per customer: %.1f\n", avgOrders)
	fmt.Printf("Total revenue: $%.2f\n", totalRevenue)
	fmt.Printf("Average customer value: $%.2f\n", avgSpent)

}

// createLargeTestData creates test data for performance optimization examples
func createLargeTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_large_example_*")
	if err != nil {
		log.Fatal(err)
	}

	customerData := `customer_id,name,email,registration_date,total_orders,total_spent
1001,Premium Customer A,premium.a@example.com,2023-01-15,15,1500.00
1002,Premium Customer B,premium.b@example.com,2023-02-20,12,1200.00
1003,Premium Customer C,premium.c@example.com,2023-03-10,10,1000.00
1004,Regular Customer D,regular.d@example.com,2023-04-05,8,800.00
1005,Regular Customer E,regular.e@example.com,2023-05-15,6,600.00
1006,Regular Customer F,regular.f@example.com,2023-06-20,5,500.00
1007,Budget Customer G,budget.g@example.com,2023-07-10,3,300.00
1008,Budget Customer H,budget.h@example.com,2023-08-25,2,200.00
1009,New Customer I,new.i@example.com,2023-09-30,1,100.00
1010,New Customer J,new.j@example.com,2023-10-15,1,100.00`

	customerFile := filepath.Join(tmpDir, "customer_summary.csv")
	err = os.WriteFile(customerFile, []byte(customerData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

Output:

=== Performance Optimization Techniques ===

1. Pagination with LIMIT and OFFSET:
Page 1:
  - Premium Customer A (ID: 1001, Orders: 15)
  - Premium Customer B (ID: 1002, Orders: 12)
  - Premium Customer C (ID: 1003, Orders: 10)
Page 2:
  - Regular Customer D (ID: 1004, Orders: 8)
  - Regular Customer E (ID: 1005, Orders: 6)
  - Regular Customer F (ID: 1006, Orders: 5)

2. Efficient filtering with indexes:
High-value customers:
  - Premium Customer A (premium.a@example.com) - Registered: 2023-01-15
  - Premium Customer B (premium.b@example.com) - Registered: 2023-02-20

3. Summary statistics:
Total customers: 10
Average orders per customer: 6.3
Total revenue: $6300.00
Average customer value: $630.00

ExampleOpen_salesAnalysis demonstrates practical sales data analysis

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

// createSalesTestData creates test data for sales analysis examples
func createSalesTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_sales_example")
	if err != nil {
		log.Fatal(err)
	}

	salesData := `order_id,customer_id,product_name,category,quantity,unit_price,order_date,region
1,101,Laptop Pro,Electronics,2,1299.99,2024-01-15,North
2,102,Wireless Mouse,Electronics,1,29.99,2024-01-16,South
3,103,Office Chair,Furniture,1,299.99,2024-01-17,East
4,101,USB Cable,Electronics,3,12.99,2024-01-18,North
5,104,Standing Desk,Furniture,1,599.99,2024-01-19,West
6,105,Bluetooth Speaker,Electronics,2,79.99,2024-01-20,South
7,106,Coffee Table,Furniture,1,199.99,2024-01-21,East
8,102,Keyboard,Electronics,1,89.99,2024-01-22,South
9,107,Monitor 24inch,Electronics,1,249.99,2024-01-23,North
10,103,Desk Lamp,Furniture,2,39.99,2024-01-24,East`

	err = os.WriteFile(filepath.Join(tmpDir, "sales.csv"), []byte(salesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	customersData := `customer_id,name,email,city,registration_date
101,John Doe,john@example.com,New York,2023-06-01
102,Jane Smith,jane@example.com,Los Angeles,2023-07-15
103,Bob Johnson,bob@example.com,Chicago,2023-08-20
104,Alice Brown,alice@example.com,Houston,2023-09-10
105,Charlie Wilson,charlie@example.com,Phoenix,2023-10-05
106,Diana Lee,diana@example.com,Philadelphia,2023-11-12
107,Frank Miller,frank@example.com,San Antonio,2023-12-03`

	err = os.WriteFile(filepath.Join(tmpDir, "customers.csv"), []byte(customersData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

func main() {
	tmpDir := createSalesTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	db, err := filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Sales summary by category and region
	query := `
		SELECT 
			category,
			region,
			COUNT(*) as order_count,
			SUM(quantity * unit_price) as total_revenue,
			AVG(quantity * unit_price) as avg_order_value,
			MIN(order_date) as first_order,
			MAX(order_date) as last_order
		FROM sales 
		GROUP BY category, region
		ORDER BY total_revenue DESC
	`

	rows, err := db.QueryContext(ctx, query)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	fmt.Println("Sales Analysis by Category and Region:")
	fmt.Println("=====================================")
	fmt.Printf("%-12s %-8s %-6s %-10s %-12s %-12s %s\n",
		"Category", "Region", "Orders", "Revenue", "Avg Order", "First Order", "Last Order")
	fmt.Println(strings.Repeat("-", 80))

	for rows.Next() {
		var category, region, firstOrder, lastOrder string
		var orderCount int
		var totalRevenue, avgOrderValue float64

		err := rows.Scan(&category, &region, &orderCount, &totalRevenue, &avgOrderValue, &firstOrder, &lastOrder)
		if err != nil {
			log.Fatal(err)
		}

		fmt.Printf("%-12s %-8s %-6d $%-9.2f $%-11.2f %-12s %s\n",
			category, region, orderCount, totalRevenue, avgOrderValue, firstOrder, lastOrder)
	}

}

Output:

Sales Analysis by Category and Region:
=====================================
Category     Region   Orders Revenue    Avg Order    First Order  Last Order
--------------------------------------------------------------------------------
Electronics  North    3      $2888.94   $962.98      2024-01-15   2024-01-23
Furniture    West     1      $599.99    $599.99      2024-01-19   2024-01-19
Furniture    East     3      $579.96    $193.32      2024-01-17   2024-01-24
Electronics  South    3      $279.96    $93.32       2024-01-16   2024-01-22

ExampleOpen_webLogAnalysis demonstrates analyzing web server logs

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/nao1215/filesql"
)

func main() {
	tmpDir := createWebLogTestData()
	defer os.RemoveAll(tmpDir)

	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	db, err := filesql.OpenContext(ctx, tmpDir)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	fmt.Println("=== Web Log Analysis ===")

	// Top pages by hits
	fmt.Println("\n1. Top Pages by Hits:")
	rows, err := db.QueryContext(ctx, `
		SELECT 
			path,
			COUNT(*) as hits,
			COUNT(DISTINCT ip_address) as unique_visitors
		FROM access_logs 
		WHERE status_code = 200
		GROUP BY path
		ORDER BY hits DESC
		LIMIT 5
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-20s %-6s %s\n", "Path", "Hits", "Unique")
	fmt.Println(strings.Repeat("-", 35))
	for rows.Next() {
		var path string
		var hits, unique int
		if err := rows.Scan(&path, &hits, &unique); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-20s %-6d %d\n", path, hits, unique)
	}
	_ = rows.Close() // Ignore close error in test cleanup

	// Error analysis
	fmt.Println("\n2. Error Analysis:")
	rows, err = db.QueryContext(ctx, `
		SELECT 
			status_code,
			COUNT(*) as error_count,
			ROUND(COUNT(*) * 100.0 / (SELECT COUNT(*) FROM access_logs), 2) as percentage
		FROM access_logs 
		WHERE status_code >= 400
		GROUP BY status_code
		ORDER BY error_count DESC
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-12s %-6s %-10s\n", "Status Code", "Count", "Percentage")
	fmt.Println(strings.Repeat("-", 30))
	for rows.Next() {
		var statusCode, errorCount int
		var percentage float64
		if err := rows.Scan(&statusCode, &errorCount, &percentage); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-12d %-6d %-10.2f%%\n", statusCode, errorCount, percentage)
	}
	_ = rows.Close() // Ignore close error in test cleanup

	// Hourly traffic pattern
	fmt.Println("\n3. Traffic by Hour:")
	rows, err = db.QueryContext(ctx, `
		SELECT 
			CAST(strftime('%H', timestamp) AS INTEGER) as hour,
			COUNT(*) as requests,
			AVG(response_time) as avg_response_time
		FROM access_logs
		GROUP BY hour
		ORDER BY hour
	`)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%-5s %-9s %-12s\n", "Hour", "Requests", "Avg Response")
	fmt.Println(strings.Repeat("-", 28))
	for rows.Next() {
		var hour, requests int
		var avgResponseTime float64
		if err := rows.Scan(&hour, &requests, &avgResponseTime); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%-5d %-9d %-12.0fms\n", hour, requests, avgResponseTime)
	}
	_ = rows.Close() // Ignore close error in test cleanup

}

// createWebLogTestData creates test data for web log analysis examples
func createWebLogTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_weblog_example_*")
	if err != nil {
		log.Fatal(err)
	}

	accessLogsData := `timestamp,ip_address,method,path,status_code,response_time,user_agent
2024-01-01 09:15:30,192.168.1.100,GET,/,200,150,Mozilla/5.0
2024-01-01 09:30:45,192.168.1.101,GET,/products,200,200,Mozilla/5.0
2024-01-01 10:05:15,192.168.1.100,GET,/,200,120,Mozilla/5.0
2024-01-01 10:20:30,192.168.1.102,GET,/about,200,180,Mozilla/5.0
2024-01-01 10:35:45,192.168.1.101,GET,/products,200,160,Mozilla/5.0
2024-01-01 11:10:15,192.168.1.103,GET,/contact,200,140,Mozilla/5.0
2024-01-01 11:25:30,192.168.1.100,GET,/,200,200,Mozilla/5.0
2024-01-01 11:40:45,192.168.1.104,GET,/missing,404,50,Mozilla/5.0
2024-01-01 14:15:30,192.168.1.105,GET,/notfound,404,100,Mozilla/5.0`

	accessLogsFile := filepath.Join(tmpDir, "access_logs.csv")
	err = os.WriteFile(accessLogsFile, []byte(accessLogsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

Output:

=== Web Log Analysis ===

1. Top Pages by Hits:
Path                 Hits   Unique
-----------------------------------
/                    3      1
/products            2      1
/contact             1      1
/about               1      1

2. Error Analysis:
Status Code  Count  Percentage
------------------------------
404          2      22.22     %

3. Traffic by Hour:
Hour  Requests  Avg Response
----------------------------
9     2         175         ms
10    3         153         ms
11    3         130         ms
14    1         100         ms

ExampleOpenContext demonstrates opening files with context support for timeout and cancellation

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"time"

	"github.com/nao1215/filesql"
)

// createTempTestData creates temporary CSV files for the example
func createTempTestData() string {
	tmpDir, err := os.MkdirTemp("", "filesql_example")
	if err != nil {
		log.Fatal(err)
	}

	employeesData := `id,name,department_id,salary,hire_date
1,Alice Johnson,1,95000,2020-01-15
2,Bob Smith,1,85000,2019-03-22
3,Charlie Brown,1,80000,2021-06-10
4,David Wilson,1,75000,2022-02-28
5,Eve Davis,2,70000,2020-09-15
6,Frank Miller,2,65000,2021-11-30
7,Grace Lee,3,60000,2019-12-05
8,Henry Taylor,3,55000,2022-04-18`

	err = os.WriteFile(filepath.Join(tmpDir, "employees.csv"), []byte(employeesData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	departmentsData := `id,name,budget,manager_id
1,Engineering,1000000,1
2,Marketing,800000,5
3,Sales,600000,7
4,HR,400000,9`

	err = os.WriteFile(filepath.Join(tmpDir, "departments.csv"), []byte(departmentsData), 0600)
	if err != nil {
		log.Fatal(err)
	}

	return tmpDir
}

func main() {
	tmpDir := createTempTestData()
	defer os.RemoveAll(tmpDir)

	// Create a context with timeout
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	// Open database with context
	db, err := filesql.OpenContext(ctx, filepath.Join(tmpDir, "employees.csv"))
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	// Query with context support
	rows, err := db.QueryContext(ctx, `
		SELECT name, salary 
		FROM employees 
		WHERE salary > 70000 
		ORDER BY salary DESC
	`)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	fmt.Println("High earners (>$70,000):")
	for rows.Next() {
		var name string
		var salary float64
		if err := rows.Scan(&name, &salary); err != nil {
			log.Fatal(err)
		}
		fmt.Printf("- %s: $%.0f\n", name, salary)
	}

}

Output:

High earners (>$70,000):
- Alice Johnson: $95000
- Bob Smith: $85000
- Charlie Brown: $80000
- David Wilson: $75000