save

Function: save

The save function ensures that all in-memory changes made to the database are persisted to disk. It updates the .table files for each table with the current state of their records and schema, making the changes permanent.

---

Declaration

void save();

Functionality

1. Iterates Through Tables The function loops through all tables registered in the tables map.

2. Retrieves Table Schema It uses the get_table_content_header method to extract the schema (header) of each table, which defines the column names and their corresponding data types.

3. Appends Records to the Table File For each table:

   • Existing file content is read and preserved up to the header.

   • New records are appended to the file in a structured format, enclosed by square brackets ([ ... ]).

4. Type-Safe Serialization Each record's values are serialized into the correct format based on their data type (INT, DOUBLE, FLOAT, BOOL, STRING). Sensitive data (e.g., strings) is compressed before being written.

5. Writes Back to the File After constructing the updated content, the function writes it back to the .table file in the database directory.

Notes

• The database must be open for this function to work. If the database is not open, the function will not execute.

• This function modifies the .table files directly in the temporary working directory.

• Compression is applied to STRING data for security purposes, reducing the risk of database compromise.

• The save function does not affect other database files; it strictly operates on .table files.

Example

Here’s a simple demonstration of how to use the save function:

#include "qic.h"
#include <iostream>
#include <unordered_map>
#include <any>

int main() {
    data_base db;

    // Open the database
    std::filesystem::path dbPath = "mydatabase.db";
    db.open_database(dbPath);

    // Create a table and add some records
    db.add_table("COMPANY", std::unordered_map<std::string, data_type>{
                                 {"ID", INT},
                                 {"NAME", STRING},
                                 {"AGE", INT},
                                 {"ADDRESS", STRING},
                                 {"SALARY", DOUBLE}});

    db.add_value("COMPANY", std::unordered_map<std::string, std::any>{
                                 {"ID", std::any(1)},
                                 {"NAME", std::any(std::string("Alice"))},
                                 {"AGE", std::any(30)},
                                 {"ADDRESS", std::any(std::string("123 Elm St"))},
                                 {"SALARY", std::any(5000.0)}});

    db.add_value("COMPANY", std::unordered_map<std::string, std::any>{
                                 {"ID", std::any(2)},
                                 {"NAME", std::any(std::string("Bob"))},
                                 {"AGE", std::any(40)},
                                 {"ADDRESS", std::any(std::string("456 Oak Ave"))},
                                 {"SALARY", std::any(7000.0)}});

    // Save all changes to the database
    db.save();

    // Close the database
    db.close();

    std::cout << "Changes saved and database closed successfully!" << std::endl;

    return 0;
}