PostgreSQL is an open-source full ACID SQL database system. Pronounced "post-grehs-Q-L", though in the case of MS SQL Server, SQL is pronounced as "sequel".
PostgreSQL is a derivitive of POSTGRES 4.2, converted to ANSI C. POSTGRES is a database management system. It is compliant with ANSI SQL92 and SQL89. It supports a number of enhancements, such as inheritance, declaritive queries, optimization, concurrency control, transactions, multi-user support, user defined operators, types, functions, and access methods. APIs exist for C, C++, Java, Perl4, Perl5, Python, SQL and Tcl. A JDBC driver is also included in the main distribution. Free drivers for ODBC are available as a separate download. A commercial version of PostgreSQL is available via Illustra, Inc. The most recent version is 7.4.
PostgreSQL was previously distributed with various language bindings, but current versions no longer include those. They are available separately.
Starting with version 8.0, the server side of Postgres is also available for native Windows (NT, 2000, XP, etc. variants only). Previous versions required Cygwin to run the PostgreSQL server. Client access libraries have always been available on Win32.
PostgreSQL and Tcl have a long history with each other. Tcl bindings such as pgtcl are available for communicating with the server from Tcl scripts, while
One of PG's technical advantages among databases is its asynchronous notification feature. Tcl's event loop nicely complements this.
pgtcl and pgtcl-ng have binaries available for windows, but aren't current (2018-01), but a couple of years old and only 32 bit. pgintcl is platform-independent and therefore can be used with any current Tcl version.
I found, that the syntax of the Pgtcl commands are not the Tcl way. So I wrote a little wrapper around the commands provided by the Pgtcl package to make them more tcl-like:
proc pg {cmd args} {
switch $cmd {
connect {pg_connect [lindex $args end]}
disconnect {pg_disconnect [lindex $args end]}
execute {pg_exec [lindex $args 0] [lindex $args 1]}
getrow {pg_result [lindex $args 0] -getTuple [lindex $args 1]}
clear {pg_result [lindex $args 0] -clear}
status {pg_result [lindex $args 0] -status}
rowcount {pg_result [lindex $args 0] -numTuples}
}
}This adds a command pg to Tcl which I like far more than the original one. Instead of saying
pg_connect "mydb" pg_disconnect $myHandle pg_result $myResult -clear
I just type
pg connect "mydb" pg disconnect $myHandle pg clear $myResult
Please note, that there is no error handling and checking in the command pg and you can easily type in wrong things. It would be best to put this command in it's own namespace and provide for error checking etc. You could even add more funcionality like a loop command for query results like in nstcl
MB 2003-11-13:
I got caught out by a problem using pg_execute. pg_execute evaluates the supplied script for each row of the result. I was appending each result to a list. The problem was that the speed scaled very poorly as the number of records increased. I boiled it down to this test case:
set a {}
time [list pg_execute pgsql5 {SELECT * FROM journal LIMIT 1000} {
append a {23456789012345678901234567890123456789012345678901234567890}}]It turned out to be because append was, of course, returning the whole variable, which was quite big. pg_execute was internally doing something slow with what was returned. Changing the test case to:
set a {}
time [list pg_execute pgsql5 {SELECT * FROM journal LIMIT 1000} {
append a {23456789012345678901234567890123456789012345678901234567890} ; list}]fixed the problem. This reduced the time to read 10,000 records from about half a minute to 170 milliseconds!