DatabaseMetaData.getColumn(). I proposed a patch that would change the
number of queries to find out all columns in a table from 2 * N + 1 to 1 (N
being the number of columns reported) by using some outer joins. I also
fixed the fact that getColumns() only returned columns that had a default
defined. OTOH, I did not use to change the code required for obtaining a
column's remarks (by using col_description() for 7.2 and requested by Tom
Lane).
Finally, I have found a way to get all the column details in a single query
*and* use col_description() for 7.2 servers. A patch is attached. It
overrules Ren? Pijlman's fix for this that was committed just today, but
still used N + 1 queries (sorry Ren? ;-) )
I also fixed the return values for TABLE_CAT and TABLE_SCHEM from "" to
null, to be more standard compliant (and requested in Ren?'s mail found at
http://fts.postgresql.org/db/mw/msg.html?mid=1034253).
As always, the JDBC1 version has not been tested as I have no JDK 1.1
Jeroen van Vianen
>there is still an unpatched reference to pg_description in
>getColumns(), in both jdbc1 and jdbc2.
This was introduced by Jeroen's patch (see
http://fts.postgresql.org/db/mw/msg.html?mid=1032468). Attached
is a patch that returns getColumns() to using "select
obj_description()" instead of direct access to pg_description,
as per the request by Tom.
I've incorporated Jeroen's fix to left outer join with
pg_attrdef instead of inner join, so getColumns() also returns
columns without a default value.
I have, however, not included Jeroen's attempt to combine
multiple queries into one huge multi-join query for better
performance, because:
1) I don't know how to do that using obj_description() instead
of direct access to pg_description
2) I don't think a performance improvement (if any) in this
method is very important
Because of the outer join, getColumns() will only work with a
backend >= 7.1. Since the conditional coding for 7.1/7.2 and
jdbc1/jdbc2 is already giving me headaches I didn't pursue a
pre-7.1 solution.
Regards,
Ren? Pijlman <rene@lab.applinet.nl>
flawed in the following ways:
1. Only returned columns that had a default value defined, rather than all
columns in a table
2. Used 2 * N + 1 queries to find out attributes, comments and typenames
for N columns.
By using some outer join syntax it is possible to retrieve all necessary
information in just one SQL statement. This means this version is only
suitable for PostgreSQL >= 7.1. Don't know whether that's a problem.
I've tested this function with current sources and 7.1.3 and patched both
jdbc1 and jdbc2. I haven't compiled nor tested the jdbc1 version though, as
I have no JDK 1.1 available.
Note the discussion in http://fts.postgresql.org/db/mw/msg.html?mid=1029626
regarding differences in obtaining comments on database object in 7.1 and
7.2. I was unable to use the following syntax (or similar ones):
select
...,
description
from
...
left outer join col_description(a.attrelid, a.attnum) description
order by
c.relname, a.attnum;
(the error was parse error at or near '(') so I had to paste the actual
code for the col_description function into the left outer join. Maybe
someone who is more knowledgable about outer joins might provide me with a
better SQL statement.
Jeroen van Vianen
system. Some systems did not understand the 'l' section, and in general
it wasn't entirely appropriate.
On SCO OpenServer, the man pages won't be installed at all until someone
figures out their man system.
This patch moves the logic that looks up TypeOid, PGTypeName, and
SQLTypeName from Field to Connection. It is moved to connection since
it needs to differ from the jdbc1 to jdbc2 versions and Connection
already has different subclasses for the two driver versions. It also
made sense to move the logic to Connection as some of the logic was
already there anyway.
Barry Lind
> Shouldn't
>
> throw new PSQLException("metadata unavailable");
>
> in getTypeInfo() be something like:
>
> throw new PSQLException("postgresql.meta.unavailable");
>
> to allow translation of the error message in the
> errors*.properties files?
You're right. Attached is an updated patch that also includes a message
in error.properties. I've attempted a French message in
errors_fr.properties but beware that I haven't written French in quite a
few years. Don't know Italian, German, or Dutch so I can't do those.
Liam Stewart
includes two changes in the JDBC driver:
1) When connected to a backend >= 7.2: use obj_description() and
col_description() instead of direct access to pg_description.
2) In DatabaseMetaData.getTables()/getColumns()/getProcedures():
when there is no comment on the object, return null in the
REMARKS column of the ResultSet, instead of the default string
"no remarks".
Change 2 first appeared as a side-effect of change 1, but it is
actually more compliant with the JDBC spec: "String object
containing an explanatory comment on the table/column/procedure,
which may be null". The default string "no remarks" was strictly
speaking incorrect, as it could not be distinguished from a real
user comment "no remarks". So I removed the default string
completely.
Change 2 might break existing code that doesn't follow the JDBC
spec and isn't prepared to handle a null in the REMARKS column
of getTables()/getColumns()/getProcedures.
Patch tested with jdbc2 against both a 7.1 and a CVS tip
backend. I did not have a jdbc1 environment to build and test
with, but since the touched code is identical in jdbc1 and jdbc2
I don't foresee any problems.
Regards,
Ren? Pijlman
1) improves performance of commit/rollback by reducing number of round
trips to the server
2) uses 7.1 functionality for setting the transaction isolation level
3) backs out a patch from 11 days ago because that code failed to
compile under jdk1.1
Details:
1) The old code was doing the following for each commit:
commit
begin
set transaction isolation level xxx
thus a call to commit was performing three round trips to the database.
The new code does this in one round trip as:
commit; begin; set transaction isolation level xxx
In a simple test program that performs 1000 transactions (where each
transaction does one simple select inside that transaction) has the
following before and after timings:
Client and Server on same machine
old new
--- ---
1.877sec 1.405sec 25.1% improvement
Client and Server on different machines
old new
--- ---
4.184sec 2.927sec 34.3% improvement
(all timings are an average of four different runs)
2) The driver was using 'set transaction isolation level xxx' at the
begining of each transaction, instead of using the new 7.1 syntax of
'set session characteristics as transaction isolation level xxx' which
only needs to be done once instead of for each transaction. This is
done conditionally (i.e. if server is 7.0 or older do the old behaviour,
else do the new behaviour) to not break backward compatibility. This
also required the movement of some code to check/test database version
numbers from the DatabaseMetaData object to the Connection object.
3) Finally while testing, I discovered that the code that was checked in
11 days ago actually didn't compile. The code in the patch for
Connection.setCatalog() used Properties.setProperty() which only exists
in JDK1.2 or higher. Thus compiling the JDBC1 driver failed as this
method doesn't exist. Thus I backed out that patch.
Barry Lind
* NULLs are sorted differently in 7.2
* table correlation names are supported
* GROUP BY, ORDER BY unrelated is supported since 6.4
* ESCAPE/LIKE only supported since 7.1
* outer joins only since 7.1
* preferred term for procedure is "function"
* preferred term for catalog is "database"
* supports SELECT for UPDATE since 6.5
* supports subqueries
* supports UNION; supports UNION ALL since 7.1
* update some of the max lengths to match reality
* rearrange some functions to match the order in the spec
for easier maintenance
Here's what I came up with. The biggest difference api between JDK1.x and
later versions is the support for collections. The problem was with the
Vector class; in jdk1.x there is no method called add, so I changed the
calls to addElement. Also no addAll, so I rewrote the method slightly to not
require addAll. While reviewing this I notices some System.out.println
statements that weren't commented out. So I commented them out in both
versions.
The upshot of all of this is that I have clean compile, but no idea if the
code works ;(
Dave Cramer
(http://www.ideit.com/products/dbvis/) to work with Postgresql and I found
out the following bug: if database has views then getTables() gets the null
pointer exception ('order by relname' makes the listing tree in
DbVisualizer a lot useful !!)
This patch should propably be applied to the the jdbc1's
DatabaseMetaData.java, too.
Panu Outinen
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
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 :)
----------------------------------------------------------------
Travis Bauer | CS Grad Student | IU |www.cs.indiana.edu/~trbauer
----------------------------------------------------------------
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
