postgresql11-pgtcl/pgtcl2.1.1/README.historical

This is the pgtcl-ng Source Release Historical README
Last updated for pgtcl-1.5.0 on 2004-02-29
The project home page is: http://gborg.postgresql.org/project/pgtclng/
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This file contains historical information about the PostgreSQL Tcl
Interface. README files distributed with predecessor projects can be found
below.  Not all of this information applies to the current release, and the
Reference Manual and current README should be considered definitive.

=============================================================================
    README from Gborg "pgtcl" project unbundled interface release 1.4b3
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libpgtcl is a library that implements Tcl commands for front-end
clients to interact with Postgresql 7.2 (and perhaps later)
backends.  See libpgtcl.doc for details.

 Id: README,v 1.6 2002/11/16 01:10:51 karl Exp

This is pgtcl version 1.4 beta 3

CHANGES IN 1.4 BETA 3

Fixed all known memory leaks.  Fixed bug in "pg_result -assignbyidx".
Fixed notifier bug in pg_listen.

VERSION 1.4

With version 1.4, Pgtcl has been internally overhauled and brought up to
date with the latest Tcl C-interface technology, while maintaining
nearly 100% compatibility with the pg_* Tcl interface provided by Pgtcl 1.3.

Most Tcl programs that used Pgtcl 1.3 will work without modification
under Pgtcl 1.4.

This is a transitional release, as pgtcl is moving out the of core and
into its own distribution.  This means that documentation also must be
collected and included.  This has not yet been done.

CONFIGURING

Pgtcl is now Tcl Extension Architecture (TEA) compliant, shipping with
a standard "configure" script.  It no longer needs to reside in a specific
place within the Postgres source tree in order to build.

You need to specify a path to the Postgres include files
using --with-postgres-include and to the Postgres libraries
using --with-postgres-lib

If you had PostgreSQL installed into /usr/postgres and a Tcl build in
/usr/pptcl, you might use something like

./configure --prefix=/usr/pptcl --with-postgres-include=/usr/postgres/include --with-postgres-lib=/usr/postgres/lib

BUILDING

Do a "make".  If all goes well, libpgtcl will be compiled and linked.

INSTALLING

Do a "make install".

USING IT

With version 1.4, Pgtcl is a standard package and can be loaded with
"package require" instead of the shared library load routine, "load".

Fire up your tclsh:

tclsh8.4
% package require Pgtcl
1.4

You should use package require instead of load because there will be
additional Tcl code shipped in future versions of Pgtcl, and using
package require will make that code available to your application.


CHANGES

The main changes are:

    o Support has been dropped for Tcl 7.x.  We now support Tcl 8.0 and above,
      preferably Tcl 8.3 and above.

    o All commands have now been converted to use Tcl 8-style Tcl objects.

        The result is a probable increase in performance in all routines, with
        potentially huge performance increases in pg_select and pg_execute when
        used with complex Tcl code bodies.

    o A new experimental asynchronous interface has been added

	Requests can be issued to the backend without waiting for the
	results, allowing for user interfaces to still work, etc.
	Also, requests can now be cancelled while they're in process.

    o pg_* call arguments are now checked much more rigorously.

	Code previously using atoi() for integer conversions now
	uses Tcl_GetIntFromObj, etc.

	pg_* calls with too many arguments were often accepted without
	complaint.  These now generate standard Tcl "wrong # args"
	messages, etc.

    o Error reporting has been brought into more compliance with the
      Tcl way of doing things.

    o TEA-compliant build and install.

So some programs that might have been working properly but had certain
syntatically incorrect pg_* commands will now fail until fixed.

pg_result -assign and pg_result -assignbyidx used to return the array
name, which was superfluous because the array name was specified on the
command line.  They now return nothing.  *** POTENTIAL INCOMPATIBILITY ***

=============================================================================
    README.async from Gborg "pgtcl" unbundled interface project
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 Id: README.async,v 1.1 2002/11/04 16:53:38 karl Exp

Experimental Tcl interface to PostgreSQL asynchronous query processing

        by Karl Lehenbauer (karl@procplace.com) 10/30/2002

RATIONALE

From the C-interface docs:

The PQexec function is adequate for submitting commands in simple
synchronous applications. It has a couple of major deficiencies however:

    * PQexec waits for the command to be completed. The application may
      have other work to do (such as maintaining a user interface), in which
      case it won't want to block waiting for the response.

    * Since control is buried inside PQexec, it is hard for the frontend
      to decide it would like to try to cancel the ongoing command. (It
      can be done from a signal handler, but not otherwise.)

    * PQexec can return only one PGresult structure. If the submitted
      command string contains multiple SQL commands, all but the last
      PGresult are discarded by PQexec.

WHAT THIS IS

A handful of new pg_* commands have been added to support asynchronous
operation, including cancelling requests that are currently being
processed and obtaining results from each SQL command when a
query contains multiple commands.

EXPERIMENTAL IN NATURE

This is a new Tcl interface to asynchronous query processing capabilities that
have been made available through the Postgres C interface.

We're calling it experimental because we think we'll want to evolve and change
the interface, perhaps simplifying it, as we gain experience with it.  So
if you use it, understand that we are not promising to provide the same
interface or backwards compatibility to this interface in future releases.

ASYNCHRONOUS QUERY PROCESSING COMMANDS

    pg_sendquery connection query

This works like pg_exec, except that the query is issued asynchronously
and pg_sendquery returns immediately without providing a result handle.

To get result handles resulting from the execution of pg_sendqery (and there
may be more than one if there are multiple SQL commands in the query), you
need to repeatedly call

    pg_getresult connection

This will return the same sort of result handle that pg_exec returns.

If there is no query currently being processed or all of the results have
been obtained, pg_getresult returns nothing.


    pg_isbusy connection

pg_getresult can block if results aren't yet available.  To avoid this,
you can use pg_isbusy to check to see if the connection is busy processing
a query.

If this returns 1, pg_getresult will block if called.  If it's 0, you can
safely call pg_getresult and it won't block.

    pg_blocking

This sets whether a connection is set for blocking or nonblocking, and
allows that state to be changed.

 syntax:
 pg_blocking connection - returns the current state, 1 = blocking, 0 = non
 pg_blocking connection 1 - sets the connection to blocking
 pg_blocking connection 0 - sets the connection to nonblocking

Note - I'm not sure about all of the ramifications of setting a connection
nonblocking.  Even with a connection in the (default) blocking state,
pg_isbusy seems to work OK and can be used in conjunction with pg_getresult
to keep from blocking while processing query results.


    pg_cancelrequest connection

This request that postgresql abandon processing of the current command
issued via pg_sendquery.

There is no guarantee that the request will be cancelled.  If it is and
you were in the middle of a transaction, the entire transaction  is cancelled.

You still need to call pg_getresult repeatedly until it doesn't return
anything, and handle (and discard) all of the returned result handles.


HOW TO USE IT

We really need some example code.  Probably we need some Tcl code that will
be part of the libary, pulled in with "package require Pgtcl", that will
issue a pg_sendrequest and iteratively call pg_isbusy on a timer, then
looping through passed-in Tcl code for each result until none are found.

You'll want to write something that issues the request via pg_sendquery.
Then you'll want a proc that does a pg_isbusy and if it is busy, calls
itself to run again after, oh, a tenth of a second or so, via "after".
If pg_isbusy returns 0, you can safely call pg_getresult to get a result.
(Use pg_result to examine the result, as in the past.)  If pg_getresult
returns an empty string, there is no more work to be done.

If you want to cancel a request that is currently in progress, use
pg_cancelrequest.  Note that you still need to do the pg_getresult
thing repeatedly until it returns nothing.  For more information, read
the C interface docs in the PostgreSQL documentation.

I know you'd like some example code.  We don't have any yet.  That's why we
call it an alpha release.

LICENSE

Berkeley License.  Freely redistributable for any use including resale,
without royalty or other sucky GPL restrictions.  Don't sue us if it
kills your dog.

=============================================================================
    README from PostgreSQL-7.4.1 bundled interfaces/libpgtcl:
-----------------------------------------------------------------------------
libpgtcl is a library that implements Tcl commands for front-end
clients to interact with the Postgresql 6.3 (and perhaps later)
backends.  See libpgtcl.doc for details.

For an example of how to build a new tclsh to use libpgtcl, see the
directory ../bin/pgtclsh

Note this version is modified by NeoSoft to have the following additional
features:

1. Postgres connections are a valid Tcl channel, and can therefore
   be manipulated by the interp command (ie. shared or transfered).
   A connection handle's results are transfered/shared with it.
   (Result handles are NOT channels, though it was tempting).  Note
   that a "close $connection" is now functionally identical to a
   "pg_disconnect $connection", although pg_connect must be used
   to create a connection.

2. Result handles are changed in format: ${connection}.<result#>.
   This just means for a connection 'pgtcl0', they look like pgtcl0.0,
   pgtcl0.1, etc.  Enforcing this syntax makes it easy to look up
   the real pointer by indexing into an array associated with the
   connection.

3. I/O routines are now defined for the connection handle.  I/O to/from
   the connection is only valid under certain circumstances: following
   the execution of the queries "copy <table> from stdin" or
   "copy <table> to stdout".  In these cases, the result handle obtains
   an intermediate status of "PGRES_COPY_IN" or "PGRES_COPY_OUT".  The
   programmer is then expected to use Tcl gets or read commands on the
   database connection (not the result handle) to extract the copy data.
   For copy outs, read until the standard EOF indication is encountered.
   For copy ins, puts a single terminator (\.).  The statement for this
   would be
	puts $conn "\\."      or       puts $conn {\.}
   In either case (upon detecting the EOF or putting the `\.', the status
   of the result handle will change to "PGRES_COMMAND_OK", and any further
   I/O attempts will cause a Tcl error.
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