data.go

package pgdump

import (
	"database/sql"
	"fmt"
	"strings"
)

// options for dumping selective tables.
type TableOptions struct {
	TableSuffix string
	TablePrefix string
	Schema      string
}

// returns a slice of table names matching options, if left blank will default to :
//
//	-> no prefix or suffix
//	-> public schema
func getTables(db *sql.DB, opts *TableOptions) ([]string, error) {
	var (
		query string
	)
	if opts != nil {
		if opts.Schema == "" {
			opts.Schema = "public"
		}
		query = fmt.Sprintf("SELECT table_name FROM information_schema.tables WHERE table_schema = '%s' AND table_name LIKE '%s'", opts.Schema, (opts.TablePrefix + "%%" + opts.TableSuffix))
	} else {
		query = "SELECT table_name FROM information_schema.tables WHERE table_schema = 'public'"
	}

	rows, err := db.Query(query)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var tables []string
	for rows.Next() {
		var tableName string
		if err := rows.Scan(&tableName); err != nil {
			return nil, err
		}
		if opts.Schema != "public" {
			tables = append(tables, opts.Schema+"."+tableName)
		} else {
			tables = append(tables, tableName)
		}
	}
	return tables, nil
}

// generates the SQL for creating a table, including column definitions.
func getCreateTableStatement(db *sql.DB, tableName string) (string, error) {
	query := fmt.Sprintf("SELECT column_name, data_type, character_maximum_length FROM information_schema.columns WHERE table_name = '%s'", tableName)
	rows, err := db.Query(query)
	if err != nil {
		return "", err
	}
	defer rows.Close()

	var columns []string
	for rows.Next() {
		var columnName, dataType string
		var charMaxLength *int
		if err := rows.Scan(&columnName, &dataType, &charMaxLength); err != nil {
			return "", err
		}
		columnDef := fmt.Sprintf("%s %s", columnName, dataType)
		if charMaxLength != nil {
			columnDef += fmt.Sprintf("(%d)", *charMaxLength)
		}
		columns = append(columns, columnDef)
	}

	return fmt.Sprintf("CREATE TABLE %s (\n    %s\n);", tableName, strings.Join(columns, ",\n    ")), nil
}

// generates the COPY command to import data for a table.
func getTableDataCopyFormat(db *sql.DB, tableName string) (string, error) {
	query := fmt.Sprintf("SELECT * FROM %s", tableName)
	rows, err := db.Query(query)
	if err != nil {
		return "", err
	}
	defer rows.Close()

	columns, err := rows.Columns()
	if err != nil {
		return "", err
	}
	values := make([]sql.RawBytes, len(columns))
	scanArgs := make([]interface{}, len(values))
	for i := range values {
		scanArgs[i] = &values[i]
	}

	var output strings.Builder
	output.WriteString(fmt.Sprintf("COPY %s (%s) FROM stdin;\n", tableName, strings.Join(columns, ", ")))
	for rows.Next() {
		err := rows.Scan(scanArgs...)
		if err != nil {
			return "", err
		}
		var valueStrings []string
		for _, value := range values {
			valueStrings = append(valueStrings, string(value))
		}
		output.WriteString(strings.Join(valueStrings, "\t") + "\n")
	}
	output.WriteString("\\.\n")

	return output.String(), nil
}

func getTableDataAsCSV(db *sql.DB, tableName string) ([][]string, error) {
	query := fmt.Sprintf("SELECT * FROM %s", tableName)
	rows, err := db.Query(query)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	columns, err := rows.Columns()
	if err != nil {
		return nil, err
	}

	output := [][]string{columns}

	values := make([]sql.RawBytes, len(columns))
	scanArgs := make([]interface{}, len(values))
	for i := range values {
		scanArgs[i] = &values[i]
	}

	for rows.Next() {
		if err := rows.Scan(scanArgs...); err != nil {
			return nil, err
		}
		var valueStrings []string
		for _, value := range values {
			if value == nil {
				valueStrings = append(valueStrings, "NULL")
			} else {
				valueStrings = append(valueStrings, string(value))
			}
		}
		output = append(output, valueStrings)
	}

	return output, nil
}