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base repository: postgresql-cfbot/postgresql
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  • 16 commits
  • 115 files changed
  • 3 contributors

Commits on Jun 18, 2025

  1. introduce new class (catalog) pg_variable 

    This table holds metadata about session variables created by
command CREATE VARIABLE, and dropped by command DROP VARIABLE.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  2. CREATE, DROP, ALTER VARIABLE 

    Implementation of commands:

    CREATE VARIABLE varname AS type
    DROP VARIABLE varname
    ALTER VARIABLE varname OWNER TO
    ALTER VARIABLE varname RENAME TO
    ALTER VARIABLE varname SET SCHEMA

ALTER command uses already prepared infrastructure based on ObjectAddress API,
so this patch implements ObjectAddress related functionality too.

Event triggers for DDL over session variables are supported.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  3. GRANT, REVOKE variable 

    Access to session variables can be controlled by SELECT or UPDATE rights. Both rights are
introduced by this patch too. Default ACL are supported.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  4. support of session variables for psql 

    This patch enhancing psql to support session variables:

 * \dV[+] command
 * tab complete for CREATE, DROP, ALTER VARIABLE

Note: tab complete for variable fencing is not supported yet
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  5. support of session variables for pg_dump 

    This patch enhancing pg_dump to support session variables.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  6. session variable fences parsing 

    The session variables can be used in query only inside the variable fence.
This is special syntax VARIABLE(varname), that eliminates a risk of
collision between variable and column identifier.

The session variables cannot be used as parameters of CALL or EXECUTE
commands. These commands evaluates arguments by direct call of expression
executor, and direct access to session variables from expression executor
will be implemented later (in next step).
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  7. local HASHTAB for currently used session variables and low level acce… 

    …ss functions

Session variables are stored in session memory in a dedicated hash table.
They are set by the LET command and read by the SELECT command.
The access rights should be checked.

Hash entries related to dropped session variables are not released. The memory
cleaning is implemented in memory-cleaning-after-DROP-VARIABLE patch.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  8. collect session variables used in plan and assign paramid 

    In the plan stage we need to collect used session variables. On the
order of this list, the param nodes gets paramid (fix_param_node).
This number is used (later) as index to buffer of values of the
used session variables. The buffer is prepared and filled by executor.

Some unsupported optimizations are disabled:

* parallel execution
* simple expression execution in PL/pgSQL
* SQL functions inlining

Before execution of query with session variables we need to collect
used session variables. This list is used for
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  9. fill an auxiliary buffer with values of session variables used in query 

    and locks variables used in query. Now we can read the content of any
session variable. Direct reading from expression executor is not allowed,
so we cannot to use session variables inside CALL or EXECUTE commands
(can be supported with direct access to session variables (from expression
executor) - postponed).

Using session variables blocks parallel query execution. It is not
technical problem (it just needs a serialization/deserialization of
es_session_varibles buffer), but it increases a size of patch (and then
it is postponed).
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  10. svariableReceiver 

    allows to store result of the query to session variable

Check correct format of result - one column, one row.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  11. LET command - assign a result of expression to the session variable 

    Implementations of EXPLAIN LET and PREPARE LET statements are not supported
now. Postponed to next step due reducing patch size.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  12. function pg_session_variables for cleaning tests 

    This is a function designed for testing and debugging.  It returns the
content of sessionvars as-is, and can therefore display entries about
session variables that were dropped but for which this backend didn't
process the shared invalidations yet.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  13. DISCARD VARIABLES 

    Implementation of DISCARD VARIABLES commands by removing hash table with session variables
and resetting related memory context.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  14. memory cleaning after DROP VARIABLE 

    Accepting a sinval message invalidates entries in the "sessionvars" hash table.
These entries are validated before any read or write operations on session variables.
When the entry cannot be validated, it is removed.  Removal will be delayed when
the variable was dropped by the current transaction, which could still be rolled back.
    [email protected] authored and Commitfest Bot committed Jun 18, 2025
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  15. plpgsql tests 

    set of plpgsql related tests:

* check session variables and plpgsql variables are not in collision ever
* check correct plpgsql plan cache invalidation when session variable is dropped
* check so the value of session variable is not corrupted, when the variable is
  modified inside nested called functions
    @laurenz
    laurenz authored and Commitfest Bot committed Jun 18, 2025
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  16. [CF 1608] v20250613 - declarative session variables, LET command 

    This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/1608

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAFj8pRDiKxpZA1+dkGK-YW_H8oYp2hVOuFpOPHEkCBc5O4Z_ug@mail.gmail.com
Author(s): Pavel Stehule
    Commitfest Bot committed Jun 18, 2025
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