[HACKERS] Eclipse Help

[Praveen M]

Hi All,

I was able to follow the debugging of the child process using this link,
https://wiki.postgresql.org/wiki/Working_with_Eclipse

As per the notes , I was able to set breakpoints and everything seem to be
working (hopefully). However I am not able to see the debug messages in the
eclipse console (for the attached process) . Please help

When I check on the console in eclipse , this is the last message I see.

0x773fad48 in poll () from /lib/x86_64-linux-gnu/libc.so.6

I added a 2 lines in pl_exec.c and kept breakpoints for these lines. The
breakpoints work fine but I am not able to see the console log.
I was able to use the log message "ereport(LOG, (errmsg("test here
started")));" in autovaccum.c line 414 and see the message in the console.
But this message is from the main process. I am having trouble seeing the
console log only for the attached process.

pl_exec.c :

Line 310 :
 ereport(LOG,
(errmsg("test here started")));

Line 311 :
elog(ERROR,"test here");

Thanks
Praveen

[HACKERS] Need to print the raw_parse_tree in the Log file

[Praveen M]

Hi All,

I would like to print the raw parse tree into the log . Is there any
internal utility function to achieve this. If there is none , can you
please help me to achieve this.

Thanks as always
Praveen

[HACKERS] CreateFunction Statement

[Praveen M]

Hi All,

I am trying to get the schema name of the create function call from the
parse tree. When I look at the structure of the CreateFunctionStmt , I do
not see the schemaname information . Can you please help me to understand
how to extract the schema name for the function.

typedef struct CreateFunctionStmt
{
NodeTag type;
bool replace; /* T => replace if already exists */
List   *funcname; /* qualified name of function to create */
List   *parameters; /* a list of FunctionParameter */
TypeName   *returnType; /* the return type */
List   *options; /* a list of DefElem */
List   *withClause; /* a list of DefElem */
} CreateFunctionStmt;

[HACKERS] Identify user requested queries

[Praveen M]

Hi All,

When the user attempts to make a connection with the database , the code
will look into various pg_catalog tables internally. However the user also
can query the pg_catalog tables. Is there a way to identify the user
requested (or typed query) vs the system requested (internal) queries?

Also what procedure or function in the code that indicates the user can
write queries , something like I wanted to know the code where the
connection is created and available for user to use.

Please Help!!

Praveen

Re: [HACKERS] Identify user requested queries

[Praveen M]

Hi Craig,

Thanks for the input. I guess i need to read more code and see if it is
achievable. I started looking into the code very recently. Your inputs is
very valuable to me. Thanks.

Yes I am trying to do something similar to multi-tenancy. I will look at
the row level security.

Thanks
Praveen

On Mon, Nov 23, 2015 at 2:16 AM, Craig Ringer  wrote:

> On 23 November 2015 at 13:27, Praveen M  wrote:
>
>> Hi All,
>>
>> When the user attempts to make a connection with the database , the code
>> will look into various pg_catalog tables internally. However the user also
>> can query the pg_catalog tables. Is there a way to identify the user
>> requested (or typed query) vs the system requested (internal) queries?
>>
>
> As far as I know there is no simple and reliable method but I'm no
> expert.
>
> Most system accesses to common catalogs use the syscache, which doesn't go
> through the SQL parse/bind/execute process. Or they construct simple scans
> directly, again bypassing the full parser. The system will run internal
> queries with the SPI though, and that's full-fledged SQL. Triggers, rules,
> views, etc, use the SPI, as does plpgsql, fulltext search, XML support, and
> a few other parts of the system. So you cannot assume that anything using
> SQL is user-originated.
>
> Take a look at PostgresMain in src/backend/tcop/postgres.c for the
> top-level user query entry point. You'll see there that you cannot rely on
> testing isTopLevel because multiple statements sent as a single query
> string are treated as if they were a nested transaction block.
> (see exec_simple_query(), postgres.c around line 962). That'd also cause
> problems with use of PL/PgSQL.
>
> You can't assume that all SPI queries are safe, because the user can run
> queries via the SPI using plpgsql etc.
>
> I don't see any way to do this without introducing the concept of a
> "system query"... and in PostgreSQL that's not simple, because the system
> query could cause the invocation of user-defined operators, functions,
> triggers, etc, that then run user-defined code. You'd have to clear the
> "system query" flag whenever you entered user-defined code, then restore it
> on exit. That seems exceedingly hard to get right reliably.
>
> Reading between the lines, it sounds like you are looking for a way to
> limit end-user access to system catalogs as part of a lockdown effort,
> perhaps related to multi-tenancy. Correct? If so, you may wish to look at
> the current work on supporting row security on system catalogs, as that is
> probably closer to what you will need.
>
>
>> Also what procedure or function in the code that indicates the user can
>> write queries , something like I wanted to know the code where the
>> connection is created and available for user to use.
>>
>
> Start reading at src/backend/tcop/postgres.c .
>
> --
>  Craig Ringer   http://www.2ndQuadrant.com/
>  PostgreSQL Development, 24x7 Support, Training & Services
>