proposal: persistent plpgsql plugin info - field plugin_info for plpgsql_function structure

Pavel Stehule escribi�:

Hello

I am working on plpgsql_check and I would to write a protection against
repeated check - so I need to mark a compiled (cached) function. Now,
plpgsql extension can store own data to exec state, and I would to some
similar for plpgsql_function. I believe so it can be useful for any plpgsql
extension that collects data per signature (and recreating) means so
refresh is necessary.

I'm not sure I understand this. Do you want to avoid running the
checker if a previous run was seen as successful and function has not
changed? Suppose the function depends on a table. I invoke the check
(it succeeds), then drop the table, then invoke the check again. What
should happen? Conversely, if I invoke the check and it fails, then I
create the table and invoke the check again, what should happen? How
does this idea of yours know when to invalidate the cached result of the
check when unrelated objects, which the function depends on, are
dropped/created/modified?

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PostgreSQL Development, 24x7 Support, Training & Services

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2013/12/31 Alvaro Herrera <alvherre@2ndquadrant.com>

Pavel Stehule escribió:

Hello

I am working on plpgsql_check and I would to write a protection against
repeated check - so I need to mark a compiled (cached) function. Now,
plpgsql extension can store own data to exec state, and I would to some
similar for plpgsql_function. I believe so it can be useful for any

plpgsql

extension that collects data per signature (and recreating) means so
refresh is necessary.

I'm not sure I understand this. Do you want to avoid running the
checker if a previous run was seen as successful and function has not
changed? Suppose the function depends on a table. I invoke the check
(it succeeds), then drop the table, then invoke the check again. What
should happen? Conversely, if I invoke the check and it fails, then I
create the table and invoke the check again, what should happen? How
does this idea of yours know when to invalidate the cached result of the
check when unrelated objects, which the function depends on, are
dropped/created/modified?

plpgsql_check is designed for interactive (active) mode and passive mode.
In interactive mode a enhanced checking is started by explicit request -
explicit using plpgsql_check function - this feature is taken from patches
that I sent to mailing list. In this mode a check is executed always (when
checking is enabled) - and it is called repeatedly (when user requests it).

Passive mode is taken from plpgsql_lint extension. It is plpgsql extension
based on begin_func callback. plpgsql_lint doesn't support fatal_errors
option - every detected error is fatal, that stops execution. plpgsql_check
allows fatal_errors = false (plpgsql_check raises warnings only], and I am
searching way how to minimize repeated warning messages. It is one
motivation. Second motivation is increasing speed of regression tests by
removing repeated check. Good idea is a function that removes mark from
compiled function - so anybody can do recheck without leaving of session.

Requested feature doesn't help me implement this concept 100%, but helps
with check If I worked with some instance of function or not. And inside
core a implementation is cheap. Outside core it is a magic with hash and
checking transaction id (about 200 lines). When I worked on extension for
coverage calculation I had to solve same task, so I think so this variable
can be useful generally for similar tasks.

Pavel Stehule <pavel.stehule@gmail.com> writes:

Requested feature doesn't help me implement this concept 100%, but helps
with check If I worked with some instance of function or not. And inside
core a implementation is cheap. Outside core it is a magic with hash and
checking transaction id (about 200 lines). When I worked on extension for
coverage calculation I had to solve same task, so I think so this variable
can be useful generally for similar tasks.

Are you proposing a reserved-for-plugins "void*" in struct
PLpgSQL_function similar to the existing one in struct PLpgSQL_execstate?

If so, while it sounds harmless in itself, I think your argument above is
actually the strongest reason *not* to do it. The existing plpgsql plugin
infrastructure is incapable of supporting more than one plugin at a time,
and the more attractive we make it, the more likely we're going to have
conflicts. It was never meant to support anything but the plpgsql
debugger. Before we start aiding and abetting the development of other
plugins, we need a design that allows more than one of them to be
installed.

regards, tom lane

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2013/12/31 Tom Lane <tgl@sss.pgh.pa.us>

Pavel Stehule <pavel.stehule@gmail.com> writes:

Requested feature doesn't help me implement this concept 100%, but helps
with check If I worked with some instance of function or not. And inside
core a implementation is cheap. Outside core it is a magic with hash and
checking transaction id (about 200 lines). When I worked on extension for
coverage calculation I had to solve same task, so I think so this

variable

can be useful generally for similar tasks.

Are you proposing a reserved-for-plugins "void*" in struct
PLpgSQL_function similar to the existing one in struct PLpgSQL_execstate?

If so, while it sounds harmless in itself, I think your argument above is
actually the strongest reason *not* to do it. The existing plpgsql plugin
infrastructure is incapable of supporting more than one plugin at a time,
and the more attractive we make it, the more likely we're going to have
conflicts. It was never meant to support anything but the plpgsql
debugger. Before we start aiding and abetting the development of other
plugins, we need a design that allows more than one of them to be
installed.

ok, what we can do better?

Can be solution a callback on plpgsql_HashTableInsert and
plpgsql_HashTableInsert? With these callbacks a relation between function
and some plugin data can be implemented more simply.

Regards

Pavel

On Wed, Jan 1, 2014 at 12:52 AM, Pavel Stehule <pavel.stehule@gmail.com> wrote:

2013/12/31 Alvaro Herrera <alvherre@2ndquadrant.com>

I'm not sure I understand this. Do you want to avoid running the
checker if a previous run was seen as successful and function has not
changed? Suppose the function depends on a table. I invoke the check
(it succeeds), then drop the table, then invoke the check again. What
should happen? Conversely, if I invoke the check and it fails, then I
create the table and invoke the check again, what should happen? How
does this idea of yours know when to invalidate the cached result of the
check when unrelated objects, which the function depends on, are
dropped/created/modified?

plpgsql_check is designed for interactive (active) mode and passive mode. In
interactive mode a enhanced checking is started by explicit request -
explicit using plpgsql_check function - this feature is taken from patches
that I sent to mailing list. In this mode a check is executed always (when
checking is enabled) - and it is called repeatedly (when user requests it).

Passive mode is taken from plpgsql_lint extension. It is plpgsql extension
based on begin_func callback. plpgsql_lint doesn't support fatal_errors
option - every detected error is fatal, that stops execution. plpgsql_check
allows fatal_errors = false (plpgsql_check raises warnings only], and I am
searching way how to minimize repeated warning messages. It is one
motivation. Second motivation is increasing speed of regression tests by
removing repeated check. Good idea is a function that removes mark from
compiled function - so anybody can do recheck without leaving of session.

Will it really help by adding different modes for plpgsql_check functionality,
is that going to help in overcoming the concerns raised by committer
which I understand was mainly about code duplication, improvement
in messages and comments in code or am I missing something?

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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