MySQL Library for MQL4 with Enhanced Memory Management
Info
The MySQL Library for MQL4 with Enhanced Memory Management is a Library for MetaTrader 4 that the original mql4-mysql. mqh library had critical memory management issues, causing crashes and instability.
Usage
This tool is typically used for enhancing chart analysis and decision making.
Platform
This Library works exclusively on MetaTrader 4 (both build 600+ and newer versions).
Setup
Place the downloaded file in MQL4/Libraries folder via File ? Open Data Folder in MetaTrader 4.
How to Install and Use MySQL Library for MQL4 with Enhanced Memory Management
1. Storage: Place library files in the MQL/Libraries directory to ensure they are accessible to your projects.
2. Implementation: Include the library in your code using the #import directive, ensuring you match the exact function names and parameters.
3. Compilation: Ensure the library is present in the directory before you compile your main EA or script, as the compiler links them during this phase.
4. Management: Keep libraries organized in sub-folders if you manage many custom functions to maintain a clean project structure.
Frequently Asked Questions
Q: What is a library file used for? A: Libraries store reusable code modules, allowing you to centralize common logic used by multiple EAs or indicators.
Q: Is a library executable? A: No, libraries are non-executable files containing functions; they must be imported into an EA, indicator, or script to function.
Q: Can I update a library while the platform is running? A: You should compile your EA or script after updating a library to ensure the latest code changes are integrated.
What this tool does
The original mql4-mysql.
Typical Use Case
This Library excels in automated trading and technical analysis on MetaTrader 4.
Compatible Platform & Setup
This Library works on MetaTrader 4. Place the file in the MQL4/Libraries folder and restart the terminal.
Description & Settings
Related: standard library - another powerful library for MetaTrader 4 traders.
The original mql4-mysql.mqh library had critical memory management issues, causing crashes and instability. After thorough code analysis, the root cause was identified within the fetcharray function, responsible for reading and saving data from the database.Also recommended: AlgLib: Numerical Analysis Library for MetaTrader - similar library with strong performance on MetaTrader 4.
To address this, modifications were made to ensure proper memory allocation and release, effectively preventing memory leaks.
The enhanced library underwent rigorous testing, demonstrating stable memory consumption over several hours and thousands of connections/data reads. The memory usage increase was minimal, less than 10 MB, likely due to the Metatrader 4 environment and running indicators.
In contrast, the original library struggled with frequent database reads and crashed within minutes.
It's crucial to note that variables should be declared as local, not global, to ensure unique memory addresses and proper release after each cycle. This is essential when using the library with Expert Advisors (EAs) or indicators.
Best practices include opening connections for specific tasks and closing them promptly after data retrieval. This minimizes the risk of reaching the maximum connection limit and crashing the server.
Additionally, proper transaction management is vital to prevent data read violations and ensure the smooth operation of EAs.
For those needing a MySQL database, the Apache server with MySQL DB is recommended as free software.
If a simple database and management tool are preferred, a user-friendly option is available.
Further guidance on database protection is provided in the linked resource.
Feedback is encouraged to refine and improve the library.
A detailed user manual can be provided upon request, covering library usage and requirements.
You may also like: Simple Unit Test Include Library for MQL4 - excellent alternative for library users on MetaTrader 4.
Source Code
#property copyright "robotfx"
#property link "https://robotfx.org"
#import "kernel32.dll"
int lstrlena(int);
void rtlmovememory(uchar &arr[],int,int);
int localfree(int); // may need to be changed depending on how the dll allocates memory
int localalloc(int,int); // added by infiniteloop
#import
#import "msvcrt.dll"
int memcpy(char &destination[],int source,int length);.......
⚠ Limitations & Risk Warning
- This tool is provided for educational and testing purposes only.
- Past performance does not guarantee future results.
- Trading involves substantial risk of loss. Use on a demo account first.
- Results may vary depending on market conditions, broker, and settings.
- We recommend thorough backtesting and forward testing before using with real funds.