Returning query results in binary format for PostgreSQL

PostgreSQL supports sending query results in text or binary format:

https://www.postgresql.org/docs/current/protocol-overview.html#PROTOCOL-FORMAT-CODES

Currently, the QSQL plugin uses a text format that is less efficient than the binary format. Other libraries like Npgsql for C# use binary format and run much faster than QPSQL.

For example, getting the SQL query result:

SELECT seq.num::boolean AS bval, 
                seq.num::integer AS intval, 
                seq.num::double precision * 0.1 AS dblval,
                'żółwik' || seq.num AS strval, 
                '2000-01-01 00:00'::timestamp + (seq.num || ' second')::interval AS tmval 
FROM (SELECT generate_series(0, 5000000) AS num) seq;

for MSVC2015 + Qt 5.12.6 it takes:
24786 msecs

and for .NET Framework 4.7.2 + Npgsql 4.1.2:
12897 msecs

The tests I did show that changing the implementation from a text to binary format would give similar results as C #:

benchmarkSequence_Libpq_binaryFormat ():
12608 msecs
benchmarkSequence_Libpq_textFormat ():
19828 msecs
benchmarkSequence_QSqlQuery ():
24786 msecs

I think it would be worth considering the binary format for QPSQL in Qt6.

Below I describe what should be done to support the binary format:

• parse binary formats for different data types (see *send i *recv functions in PostgreSQL src\backend\utils\adt directory and https://www.npgsql.org/doc/dev/type-representations.html)
• split SQL queries into individual SQL commands and use the PQsendQueryParams () function with the resultFormat = 1 parameter instead of PQsendQuery ()
• drop support for PostgreSQL 7.3, because it does not support binary format