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Home/ Questions/Q 3461
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hoz
hoz

hoz

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hoz
Asked: December 26, 20202020-12-26T13:35:31+00:00 2020-12-26T13:35:31+00:00In: Forex Expert Advisors

Question on using SQLite in experts

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I understand that someone uses SQLite in their trading experts. Reading the SQLite documentation I didn’t understand one thing:

A call to sqlite3_initialize() is an “effective” call if it is
the first time sqlite3_initialize() is invoked during the lifetime of
the process, or if it is the first time sqlite3_initialize() is invoked
following a call to sqlite3_shutdown(). Only an effective call
of sqlite3_initialize() does any initialization. All other calls
are harmless no-ops.

A call to sqlite3_shutdown() is an “effective” call if it is the first
call to sqlite3_shutdown() since the last sqlite3_initialize(). Only
an effective call to sqlite3_shutdown() does any deinitialization.
All other valid calls to sqlite3_shutdown() are harmless no-ops.

As I understand it, sqlite3_initialize() and sqlite3_shutdown() are dB initialization and deinitialization, respectively. But I couldn’t even imagine why. In theory, the database has all the data that you need to get, and if not, they will be recorded in the process. Then why initialize it? I hope there is someone here to discuss this with. Then so far everything is clear. It is clear that you can score not not use these methods, but as an option to understand the need or non-need, and not just score.

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    1. yuba

      yuba

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      yuba
      2020-12-26T13:35:57+00:00Added an answer on December 26, 2020 at 1:35 pm

      Rashit Ibatullin:

      SQLite is really a very fast and compact database. It has an equally wonderful shell-the SQLite Studio DBMS.

      Another distinguishing feature from desktop databases is that it can be logged, which has repeatedly saved my databases from hard reboots of the computer.

      I myself wrote the engine for SQLite in C#, nothing complicated. In the case of MQL5, you need to make the engine in the form of a dll, and call it using the language.

      It also seems to me that it is easier to link SQLite to the terminal through your DLL than to import the SQLite dll directly into the terminal.

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    2. irash

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      irash
      2020-12-26T13:35:53+00:00Added an answer on December 26, 2020 at 1:35 pm

      SQLite is really a very fast and compact database. It has an equally wonderful shell-the SQLite Studio DBMS.

      Another distinguishing feature from desktop databases is that it can be logged, which has repeatedly saved my databases from hard reboots of the computer.

      I myself wrote the engine for SQLite in C#, nothing complicated. In the case of MQL5, you need to make the engine in the form of a dll, and call it using the language.

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    3. mesaoria

      mesaoria

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      mesaoria
      2020-12-26T13:35:46+00:00Added an answer on December 26, 2020 at 1:35 pm

      Artiom Morochin:
      Judging from the description, if sqlite is used on the OS installed on the computer, then these functions are not needed.

      It can’t be used anywhere else 🙂 as the developers themselves write, Think of SQLite not as a replacement for Oracle but as a replacement for fopen().

      With sqlite, it is very important to think about how the database will be used, because you can run into sudden speed failures.

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    4. artamir

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      artamir
      2020-12-26T13:35:40+00:00Added an answer on December 26, 2020 at 1:35 pm

      Viktar Dzemikhau:

      I understand that someone uses SQLite in their trading experts. Reading the SQLite documentation I didn’t understand one thing:

      As I understand it, sqlite3_initialize() and sqlite3_shutdown() are dB initialization and deinitialization, respectively. But I couldn’t even imagine why. In theory, the database has all the data that you need to get, and if not, they will be recorded in the process. Then why initialize it? I hope there is someone here to discuss this with. Then so far everything is clear. It is clear that you can score not not use these methods, but as an option to understand the need or non-need, and not just score.

      Judging from the description, if sqlite is used on the OS installed on the computer, then these functions are not needed.

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    5. yuba

      yuba

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      yuba
      2020-12-26T13:35:34+00:00Added an answer on December 26, 2020 at 1:35 pm

      There are only 6-7 high-level teams that are really needed. Save the rest for better timesSee docks where in 5 minutes or less.

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