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/**
* @file veil_config.c
* \code
* Author: Marc Munro
* Copyright (c) 2006-2011 Marc Munro
* License: BSD
*
* \endcode
* @brief
* Code for setting and reading configuration data.
*
*/
#include "postgres.h"
#include "storage/fd.h"
#include "utils/guc.h"
#include "veil_version.h"
#include "veil_funcs.h"
/**
* The number of buckets to create in the hash for shared variables.
* This defaults to 32 and may be defined in postgresql.conf using eg:
* "veil.shared_hash_elems = 64"
*/
static int shared_hash_elems = 32;
/**
* The number of databases within the db cluster that will use veil.
* Every veil-using database within the cluster will get the same
* allocation of shared memory.
*/
static int dbs_in_cluster = 2;
/**
* The size in KBytes, of each of Veil's shared memory contexts. Veil
* will pre-allocate (from Postgres 8.2 onwards) twice this amount of
* shared memory, one for each context area.
* The default is 16384 Bytes and may be defined in postgresql.conf
* using eg: "veil.shmem_context_size = 8192"
*/
static int shmem_context_size = 16384;
/**
* Return the number of databases, within the database cluster, that
* will use Veil. Each such database will be allocated 2 chunks of
* shared memory (of shmem_context_size), and a single LWLock.
* It defaults to 1 and may be defined in postgresql.conf using eg:
* "veil.dbs_in_cluster = 2"
*/
int
veil_dbs_in_cluster()
{
veil_load_config();
return dbs_in_cluster;
}
/**
* Return the number of entries that should be allocated for shared
* variables in our shared hashes. This defaults to 32 and may be
* defined in postgresql.conf using eg:
* "veil.shared_hash_elems = 64"
*/
int
veil_shared_hash_elems()
{
veil_load_config();
return shared_hash_elems;
}
/**
* Return the amount of shared memory to be requested for each of the
* two shared memory contexts. This variable has no effect unless
* shared_preload_libraries has been defined in postgresql.conf to load
* the Veil shared library
* Note that this must be large enough to allocate at least one chunk of
* memory for each veil-using database in the Postgres cluster. It
* defaults to 16K and may be defined in postgresql.conf using eg:
* "veil.shmem_context_size = 16384"
*/
int
veil_shmem_context_size()
{
veil_load_config();
return shmem_context_size;
}
/**
* Initialise Veil's use of GUC variables.
*/
void
veil_config_init()
{
static bool first_time = true;
if (!first_time) {
return;
}
DefineCustomIntVariable("veil.dbs_in_cluster",
"The number of databases within the cluster "
"that will be using veil (1)",
NULL,
&dbs_in_cluster,
1, 1, 16,
PGC_USERSET,
0, NULL, NULL, NULL);
DefineCustomIntVariable("veil.shared_hash_elems",
"The number of entries for shared variables in "
"each shared memory context (32)",
NULL,
&shared_hash_elems,
32, 32, 8192,
PGC_USERSET,
0, NULL, NULL, NULL);
DefineCustomIntVariable("veil.shmem_context_size",
"Size of each shared memory context",
"Size of each shared memory context in bytes. "
"This cannot be increased without stopping "
"and restarting the database cluster.",
&shmem_context_size,
4096, 4096, 104857600,
PGC_USERSET,
0, NULL, NULL, NULL);
first_time = false;
}
/**
* Retrieve Veil's GUC variables for this session.
*/
void
veil_load_config()
{
static bool first_time = true;
if (!first_time) {
return;
}
dbs_in_cluster = atoi(GetConfigOption("veil.dbs_in_cluster", FALSE, FALSE));
shared_hash_elems = atoi(GetConfigOption("veil.shared_hash_elems",
FALSE, FALSE));
shmem_context_size = atoi(GetConfigOption("veil.shmem_context_size",
FALSE, FALSE));
first_time = false;
}
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