No support for JSON type with MySQL 8 ?
lazarus / 16-Databases

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MarcP · 2024-06-03 06:10

Hi,
With FPC version 3.2.2+dfsg-32 I'm connecting to a MySQL 8 database,
however it seems to ignore a field if it's type is JSON. (
https://dev.mysql.com/doc/refman/8.0/en/json.html )
Accessing the field's name with
query.FieldByName('MyJSONData').AsString results in a "field not
found" exception.
Listing all the fields in a request like this :

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
Query.SQL.Text := 'SELECT * FROM MyTable';    Query.Open;    try     
for i := 0 to Query.FieldCount - 1 do        WriteLn('Field ', i + 1,
': ', Query.Fields[i].FieldName);    finally      Query.Close;    end;
Will just ignore the JSON one.
Is support planned, even if working only with a .AsString ?

(If other people run into the same issue, I was able to get my data
with this, but it's not pretty) :
Code: SQL  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i SELECT
JSON_UNQUOTE(JSON_EXTRACT(JSONData, "$")) AS JSONData
Thanks for any help !

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Zvoni · 2024-06-03 06:51

As far as i understood the official MySQL-Docs:
Probably no support planned, since even MySQL doesn't ship an
"official" JSON-Datatype when calling "mysql_fetch_field_direct"
https://dev.mysql.com/doc/c-api/8.0/en/c-api-data-structures.html

https://dev.mysql.com/doc/refman/8.4/en/json.html
QuoteOptimized storage format. JSON documents stored in JSON columns
are converted to an internal format that permits quick read access to
document elements. When the server later must read a JSON value stored
in this binary format, the value need not be parsed from a text
representation. The binary format is structured to enable the server
to look up subobjects or nested values directly by key or array index
without reading all values before or after them in the document.
That said: It's still a guess on my side without being able to
actually directly test/debug what mysql_fetch_field_direct actually
returns