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Attached is a set of patches for a couple of bugs dealing with
timestamps in JDBC.
Bug#1) Incorrect timestamp stored in DB if client timezone different
than DB.
timestamps in JDBC.
Bug#1) Incorrect timestamp stored in DB if client timezone different
than DB.
The buggy implementation of setTimestamp() in PreparedStatement simply
used the toString() method of the java.sql.Timestamp object to convert
to a string to send to the database. The format of this is yyyy-MM-dd
hh:mm:ss.SSS which doesn't include any timezone information. Therefore
the DB assumes its timezone since none is specified. That is OK if the
timezone of the client and server are the same, however if they are
different the wrong timestamp is received by the server. For example if
the client is running in timezone GMT and wants to send the timestamp
for noon to a server running in PST (GMT-8 hours), then the server will
receive 2000-01-12 12:00:00.0 and interprete it as 2000-01-12
12:00:00-08 which is 2000-01-12 04:00:00 in GMT. The fix is to send a
format to the server that includes the timezone offset. For simplicity
sake the fix uses a SimpleDateFormat object with its timezone set to GMT
so that '+00' can be used as the timezone for postgresql. This is done
as SimpleDateFormat doesn't support formating timezones in the way
postgresql expects.
Bug#2) Incorrect handling of partial seconds in getting timestamps from
the DB
When the SimpleDateFormat object parses a string with a format like
yyyy-MM-dd hh:mm:ss.SS it expects the fractional seconds to be three
decimal places (time precision in java is miliseconds = three decimal
places). This seems like a bug in java to me, but it is unlikely to be
fixed anytime soon, so the postgresql code needed modification to
support the java behaviour. So for example a string of '2000-01-12
12:00:00.12-08' coming from the database was being converted to a
timestamp object with a value of 2000-01-12 12:00:00.012GMT-08:00. The
fix was to check for a '.' in the string and if one is found append on
an extra zero to the fractional seconds part.
Bug#3) Performance problems
In fixing the above two bugs, I noticed some things that could be
improved. In PreparedStatement.setTimestamp(),
PreparedStatement.setDate(), ResultSet.getTimestamp(), and
ResultSet.getDate() these methods were creating a new SimpleDateFormat
object everytime they were called. To avoid this unnecessary object
creation overhead, I changed the code to use static variables for
keeping a single instance of the needed formating objects.
Also the code used the + operator for string concatenation. As everyone
should know this is very inefficient and the use of StringBuffers is
prefered.
I also did some cleanup in ResultSet.getTimestamp(). This method has
had multiple patches applied some of which resulted in code that was no
longer needed. For example the ISO timestamp format that postgresql
uses specifies the timezone as an offset like '-08'. Code was added at
one point to convert the postgresql format to the java one which is
GMT-08:00, however the old code was left around which did nothing. So
there was code that looked for yyyy-MM-dd hh:mm:sszzzzzzzzz and
yyyy-MM-dd hh:mm:sszzz. This second format would never be encountered
because zzz (i.e. -08) would be converted into the former (also note
that the SimpleDateFormat object treats zzzzzzzzz and zzz the same, the
number of z's does not matter).
There was another problem/fix mentioned on the email lists today by
mcannon@internet.com which is also fixed by this patch:
Bug#4) Fractional seconds lost when getting timestamp from the DB
A patch by Jan Thomea handled the case of yyyy-MM-dd hh:mm:sszzzzzzzzz
but not the fractional seconds version yyyy-MM-dd hh:mm:ss.SSzzzzzzzzz.
The code is fixed to handle this case as well.
Barry Lind
drivers.
The first fix fixes the PreparedStatement object to not allocate
unnecessary objects when converting native types to Stings. The old
code used the following format:
(new Integer(x)).toString()
whereas this can more efficiently be occompilshed by:
Integer.toString(x);
avoiding the unnecessary object creation.
The second fix is to release some resources on the close() of a
ResultSet. Currently the close() method on ResultSet is a noop. The
purpose of the close() method is to release resources when the ResultSet
is no longer needed. The fix is to free the tuples cached by the
ResultSet when it is closed (by clearing out the Vector object that
stores the tuples). This is important for my application, as I have a
cache of Statement objects that I reuse. Since the Statement object
maintains a reference to the ResultSet and the ResultSet kept references
to the old tuples, my cache was holding on to a lot of memory.
Barry Lind
added to support character set encodings. However I noticed that the
encoding that is used isn't obtained from the DB. Since Java uses
unicode UCS2 internally the character set encoding is used to translate
strings from/to the DB encoding. So it seems logical that the code
would get the encoding from the DB instead of the current method of
requiring the user pass it as a parameter.
Attached is a patch that gets the DB encoding from the DB in the same
manner as is done in libpq/fe-connect.c. The patch is created off of
the latest CVS sources (Connection.java version 1.10).
Barry Lind
edition of the driver did not compile. I have fixed both issues again. I have
attached the modified files to this email, maybe you can check them into the
repository. (Fixes are marked with //FIXME). Enterprise edition driver now
compiles and seems to work.
Jan Thomae
couldn't produce a full patch using cvs diff -c this time since I have
created new files and anonymous cvs usage doesn't allow you to
adds. I'm supplying the modified src/interfaces/jdbc as a tarball at :
http://www.candleweb.no/~gunnar/projects/pgsql/postgres-jdbc-2000-10-05.tgz
The new files that should be added are :
? org/postgresql/PGStatement.java
? org/postgresql/ObjectPool.java
? org/postgresql/ObjectPoolFactory.java
There is now a global static pool of free byte arrays and used byte arrays
connected to a statement object. This is the role of the new PGStatement
class. Access to the global free array is synchronized, while we rely on
the PG_Stream synchronization for the used array.
My measurements show that the perfomance boost on this code is not quite as
big as my last shot, but it is still an improvement. Maybe some of the
difference is due to the new synchronization on the global array. I think I
will look into choosing between on a connection level and global level.
I have also started experimented with improving the performance of the
various conversions. The problem here is ofcourse related handle the
various encodings. One thing I found to speed up ResultSet.getInt() a lot
was to do custom conversion on the byte array into int instead of going
through the getString() to do the conversion. But I'm unsure if this is
portable, can we assume that a digit never can be represented by more than
one byte ? It works fine in my iso-latin-8859-1 environment, but what about
other environments ? Maybe we could provide different ResultSet
implementations depending on the encoding used or delegate some methods of
the result set to an "converter class".
Check the org/postgresql/jdbc2/FastResultSet.java in the tarball above to
see the modified getInt() method.
Regards,
Gunnar
one-line change necessary. Due to the Mark Holloman "New Relkind for
Views" patch, my support for views in the driver will need to be updated
to match. The change to DatabaseMetaData.getTableTypes[][] is as
follows:
- {"VIEW", "(relkind='r' and relhasrules='t' and relname !~
'^pg_' and relname !~ '^xinv')"},
+ {"VIEW", "(relkind='v' and relname !~ '^pg_' and relname
!~ '^xinv')"},
Christopher Cain
driver if the translations files have not been properly installed. (We
carefully avoided installing the translations file in a controlled
environment here specifically to test for such a bug. :-)
See attached description for more details.
William
--
William Webber william@peopleweb.net.au
This is a patch which lets the DatabaseMetaData return the object type
when getTables(....) is called. It does not really fix any bug, but it
fills in some functionality that should be there anyway. The diff
included here is off of the CVS as of just now :)
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Travis Bauer | CS Grad Student | IU |www.cs.indiana.edu/~trbauer
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encountered while getting my reporting tool up and running with the
driver. All changes are in the DatabaseMetaData class.
Problem: The getDatabaseProductVersion() method was returning "6.5.2"
Resolution: Changed it to return "7.0.2"
Problem: A call to getTables() with an unsupported table type (in the
String array) resulted in a malformed SQL statement and subsequent
parsing error
Resolution: Unsupported table types are now ignored without error
Problem: In a getTables() call, tables and views were both returned by
the "TABLE" table type, and the "VIEW" table type was unsupported
Resolution: Changed the "TABLE" type to return only physical tables and
added support for the "VIEW" table type (returning only views)
Problem: The getIdentifierQuoteString() method was returning null
Resolution: This method now returns a double-quote
Christopher Cain
absolute. It also makes it more compliant with the interface
specification in Sun's documentation;
1. absolute(0) should throw an exception.
2. absolute(>num-records) should set the current row to after the last
record in addition to returning false.
3. absolute(<num-records) should set the current row to before the first
record in addition to returning false.
These operations in the existing code just return false and don't change
current_row.
These changes required a minor change to relative(int) since it calls
absolute(int)
The attached patch is against the cvs repository tree as of this morning.
Also, who is in charge of maintaining the jdbc driver? I'm working on
getArray for the jdbc2 driver, but it's going to require three more
classes to be added to the driver, and thus three more source files
in the repository. Is there someone I can contact directly to ask about
this?
Travis Bauer | CS Grad Student | IU |www.cs.indiana.edu/~trbauer
It addresses three issues:
1. The problem with ResultSet's interface specifying 1-based indexing was
not quite fixed in 7.0.2. absolute would stop the user form moving to the
first record (record 0 internally).
2. Absolute did not set current_row
3. For field.mod=-1, GetObject would try to return numeric values with a
precision of around 65000. Now GetObject detects when field.mod==-1, and
passes that as the scale to getBigDecimal. getBigDecimal detects when a
-1 is passed and simply does not scale the value returned. You still get
the correct value back, it simply does not tweak the precision.
I'm working off of a source tree I just checked out from the
repository. The diff is based on what was in the repository about ten
minutes ago.
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Travis Bauer | CS Grad Student | IU |www.cs.indiana.edu/~trbauer
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Fixed Statement, so that the update count is valid when an SQL DELETE operation is done.
While fixing the update count, made it easier to get the OID of the last insert as well. Example is in example/basic.java
I'm including a diff of
postgresql-7.0/src/interfaces/jdbc/org/postgresql/jdbc2/ResultSet.java.
I've clearly marked all the fixes I did. Would *someone* who has access
to the cvs please put this in?
Joseph Shraibman
