mirror of
https://github.com/postgres/postgres.git
synced 2025-06-16 06:01:02 +03:00
cc5f81366c
Tuples can have type RECORDOID and a typmod number that identifies a blessed TupleDesc in a backend-private cache. To support the sharing of such tuples through shared memory and temporary files, provide a typmod registry in shared memory. To achieve that, introduce per-session DSM segments, created on demand when a backend first runs a parallel query. The per-session DSM segment has a table-of-contents just like the per-query DSM segment, and initially the contents are a shared record typmod registry and a DSA area to provide the space it needs to grow. State relating to the current session is accessed via a Session object reached through global variable CurrentSession that may require significant redesign further down the road as we figure out what else needs to be shared or remodelled. Author: Thomas Munro Reviewed-By: Andres Freund Discussion: https://postgr.es/m/CAEepm=0ZtQ-SpsgCyzzYpsXS6e=kZWqk3g5Ygn3MDV7A8dabUA@mail.gmail.com
45 lines
1.2 KiB
C
45 lines
1.2 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* session.h
|
|
* Encapsulation of user session.
|
|
*
|
|
* Copyright (c) 2017, PostgreSQL Global Development Group
|
|
*
|
|
* src/include/access/session.h
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
#ifndef SESSION_H
|
|
#define SESSION_H
|
|
|
|
#include "lib/dshash.h"
|
|
|
|
/* Defined in typcache.c */
|
|
typedef struct SharedRecordTypmodRegistry SharedRecordTypmodRegistry;
|
|
|
|
/*
|
|
* A struct encapsulating some elements of a user's session. For now this
|
|
* manages state that applies to parallel query, but it principle it could
|
|
* include other things that are currently global variables.
|
|
*/
|
|
typedef struct Session
|
|
{
|
|
dsm_segment *segment; /* The session-scoped DSM segment. */
|
|
dsa_area *area; /* The session-scoped DSA area. */
|
|
|
|
/* State managed by typcache.c. */
|
|
SharedRecordTypmodRegistry *shared_typmod_registry;
|
|
dshash_table *shared_record_table;
|
|
dshash_table *shared_typmod_table;
|
|
} Session;
|
|
|
|
extern void InitializeSession(void);
|
|
extern dsm_handle GetSessionDsmHandle(void);
|
|
extern void AttachSession(dsm_handle handle);
|
|
extern void DetachSession(void);
|
|
|
|
/* The current session, or NULL for none. */
|
|
extern Session *CurrentSession;
|
|
|
|
#endif /* SESSION_H */
|