Problems with transactions handling Why does psycopg2 leave database sessions “idle in transaction”?Psycopg normally starts a new transaction the first time a query isexecuted, e.g. Calling, even if the command is aSELECT. The transaction is not closed until an explicitor.If you are writing a long-living program, you should probably make sure tocall one of the transaction closing methods before leaving the connectionunused for a long time (which may also be a few seconds, depending on theconcurrency level in your database). Alternatively you can use aconnection in mode to avoid a new transaction tobe started at the first command.
I receive the error current transaction is aborted, commands ignored until end of transaction block and can’t do anything else! There was a problem in the previous command to the database, whichresulted in an error. The database will not recover automatically fromthis condition: you must run a before sendingnew commands to the session (if this seems too harsh, remember thatPostgreSQL supports nested transactions using the command). Why do I get the error current transaction is aborted, commands ignored until end of transaction block when I use multiprocessing (or any other forking system) and not when use threading? Psycopg’s connections can’t be shared across processes (but are threadsafe). If you are forking the Python process make sure to create a newconnection in each forked child. See for furtherinformations.
Problems with type conversions Why does cursor.execute raise the exception can’t adapt? Psycopg converts Python objects in a SQL string representation by lookingat the object class. The exception is raised when you are trying to passas query parameter an object for which there is no adapter registered forits class. See for informations. I can’t pass an integer or a float parameter to my query: it says a number is required, but it is a number!In your query string, you always have to use%s placeholders,even when passing a number. All Python objects are converted by Psycopgin their SQL representation, so they get passed to the query as strings.See.
DEC2FLOAT = psycopg2. Newtype ( psycopg2.
InternalError: current transaction is aborted, commands ignored until end of transaction block Showing 1-11 of 11 messages. Jul 2, 2013 - ERROR: current transaction is aborted, commands ignored until end of transaction block. Developers either love or hate this PostgreSQL,.
Values, 'DEC2FLOAT', lambda value, curs: float ( value ) if value is not None else None ) psycopg2. Registertype ( DEC2FLOAT )See to read the relevantdocumentation. If you find psycopg2.extensions.DECIMAL not available, usepsycopg2.psycopg.DECIMAL instead. Psycopg automatically converts PostgreSQL json data into Python objects. How can I receive strings instead?The easiest way to avoid JSON parsing is to register a no-op function with. Best practices When should I save and re-use a cursor as opposed to creating a new one as needed?
Cursors are lightweight objects and creating lots of them should not poseany kind of problem. But note that cursors used to fetch result sets willcache the data and use memory in proportion to the result set size. Oursuggestion is to almost always create a new cursor and dispose old ones assoon as the data is not required anymore (call onthem.) The only exception are tight loops where one usually use the samecursor for a whole bunch of INSERTs or UPDATEs. When should I save and re-use a connection as opposed to creating a new one as needed? Creating a connection can be slow (think of SSL over TCP) so the bestpractice is to create a single connection and keep it open as long asrequired.
It is also good practice to rollback or commit frequently (evenafter a single SELECT statement) to make sure the backend is neverleft “idle in transaction”. See also for lightweightconnection pooling. What are the advantages or disadvantages of using named cursors? The only disadvantages is that they use up resources on the server andthat there is a little overhead because at least two queries (one tocreate the cursor and one to fetch the initial result set) are issued tothe backend. The advantage is that data is fetched one chunk at a time:using small values it is possible to use verylittle memory on the client and to skip or discard parts of the result set. How do I interrupt a long-running query in an interactive shell?Normally the interactive shell becomes unresponsive to Ctrl-C whenrunning a query. Using a connection in green mode allows Python toreceive and handle the interrupt, although it may leave the connectionbroken, if the async callback doesn’t handle the KeyboardInterruptcorrectly.Starting from psycopg 2.6.2, the callbackcan handle a Ctrl-C correctly.
For previous versions, you can use. Problems compiling and installing psycopg2 Psycopg 2.8 fails to install, Psycopg 2.7 was working fine. With Psycopg 2.7 you were installing binary packages, but they have provenunreliable so now you have to install them explicitly using thepsycopg2-binary package. See for all thedetails.
I can’t compile psycopg2: the compiler says error: Python.h: No such file or directory. What am I missing? You need to install a Python development package: it is usually calledpython-dev. I can’t compile psycopg2: the compiler says error: libpq-fe.h: No such file or directory. What am I missing?
You need to install the development version of the libpq: the package isusually called libpq-dev. Psycopg2 raises ImportError with message psycopg.so: undefined symbol: lotruncate when imported.This means that Psycopg was compiled with support ( i.e.the libpq used at compile time was version = 8.3) but at runtime an olderlibpq dynamic library is found.Fast-forward several years, if the message reports undefined symbol:lotruncate64 it means that Psycopg was built with large objects 64 bitsAPI support ( i.e. The libpq used at compile time was at least 9.3) butat runtime an older libpq dynamic library is found.You can use.
$ ldd /path/to/packages/psycopg2/psycopg.so grep libpqto find what is the libpq dynamic library used at runtime.You can avoid the problem by using the same version of thepgconfig at install time and the libpq at runtime. Psycopg raises ImportError: cannot import name tz on import in modwsgi / ASP, but it works fine otherwise.
If psycopg2 is installed in an (e.g. Because installed byeasyinstall), the user running the program may be unable towrite in the.
Set the env variablePYTHONEGGCACHE to a writable directory. With modwsgi you canuse the directive.
Desember 2011 05.25.22 skrev Jan Bakuwel: Of course I can start testing existing values in the database before accepting them in the user interface but that's putting the horse behind the cart.