Обсуждение: Re: PQgetvalue failed to return column value for non-text data in binary format
Thank you for your comment about text and binary format. To use text, I thought one will have to construct the insert sql statement on the fly, which will incurs server parsing, syntax checking followed by execution. With binary format, I can simply prepare a statement and then update each binded parameter prior to execute the prepared statement over each records. Is there a way for me to prepare the insert statment and pass in text instead of, say, double precision? I experimented with that the the server reject the insert statement with "mismatched datatype" error. Jeff
Re: Re: PQgetvalue failed to return column value for non-text data in binary format
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Andrew McNamara
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>Thank you for your comment about text and binary format. To use text, I >thought one will have to construct the insert sql statement on the fly, >which will incurs server parsing, syntax checking followed by >execution. With binary format, I can simply prepare a statement and >then update each binded parameter prior to execute the prepared >statement over each records. > >Is there a way for me to prepare the insert statment and pass in text >instead of, say, double precision? I experimented with that the the >server reject the insert statement with "mismatched datatype" error. Certainly. Whether you use PQexecParams, or PQprepare and PQexecPrepared, you can pass text or binary parameters. But I would suggest starting with PQexecParams and getting that right before moving on to prepared statements. A overly simple example of PQexecParams usage: PGresult *res; int i; const int l = 4; const char *param_vals[l]; param_vals[0] = "10"; param_vals[1] = "20"; param_vals[2] = "30"; param_vals[3] = "40"; res = PQexecParams(conn,"INSERT INTO foo VALUES ($1,$2,$3,$4)", l, NULL, param_vals, NULL, NULL, 0); >Does someone out there has some example(s) of converting the >PostgreSQL's internal (network byte order) representation of float4, >flost8, date, datetime and timestamp into Win32 float, double, CTime or >any Win32 date/time construct under Intel x86 h/w architecture? I'd recommend against using binary args until you've got things working seemlessly with text (and maybe not even then)... I have enough grey hairs to prove the folly trying to use the binary interface. -- Andrew McNamara, Senior Developer, Object Craft http://www.object-craft.com.au/