Hi,
Please bear with me if I am completely wrong, I am a simple toolmaker and no
database specialist.
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MSEide+MSEgui includes a fork of the Free Pascal SQLdb framework. There users
provide arbitrary SQL-statements and MSEgui provides the returned data in
different forms.
In FB 2.5 we had to prepare the statement in order to be able to setup the
data buffers before calling execute. Preparing a statement AFAIK includes a
server roundtrip with its latency. This is a drawback compared with other
popular databases where no additional roundtrip is necessary.
I hoped that that necessity does not exist anymore in the new OO-API of FB3
but I could not find out how to work with arbitrary statements without
prepare.
In FB3 OO-API we have to know if the statement is a select statement which
returns a cursor or another statement kind which provides no cursor.
In the first case we call openCursor(), in the second execute().
If the non-cursor statement returns data we have to provide a data buffer and
an IMessageMetada interface which describes the structure of the buffer to
execute().
The only possibility I found to get the needed information is to call
IAttachment.prepare() with PREPARE_PREFETCH_METADATA which AFAIK again
includes a server roundtrip.
In case of openCursor() the structure of the output buffer can be found by
calling IResultSet.getMetadata().
A convenient solution of the dilemma would be if openCursor() would work with
any SQL statement.
It seems that a part of that solution already works, calling openCursor() with
"
insert into TABLE1 (STR1) values ('aabbccdd') returning PK
"
and getting result metadata by calling getMetadata() on the returned
IResultSet actually returns a valid buffer description. What apparently not
works yet is calling fetchNext(), it throws a
"
Cursor is not open
"
error.
Thanks, Martin
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