Skip to content

Commit 2159e69

Browse files
kvapkvap
committed
Implement a key-value table in shared memory with getter, setter and list methods.
1 parent 8f21156 commit 2159e69

File tree

6 files changed

+269
-0
lines changed

6 files changed

+269
-0
lines changed

‎contrib/raftable/Makefile

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,14 @@
1+
MODULES = raftable
2+
EXTENSION = raftable
3+
DATA = raftable--1.0.sql
4+
5+
ifdef USE_PGXS
6+
PG_CONFIG = pg_config
7+
PGXS := $(shell $(PG_CONFIG) --pgxs)
8+
include $(PGXS)
9+
else
10+
subdir = contrib/raftable
11+
top_builddir = ../..
12+
include $(top_builddir)/src/Makefile.global
13+
include $(top_srcdir)/contrib/contrib-global.mk
14+
endif

‎contrib/raftable/README

Lines changed: 28 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,28 @@
1+
This extension allows you to have a key-value table replicated between several
2+
Postgres instances over Raft protocol.
3+
4+
C API:
5+
/* Gets value by key. Returns the value or NULL if not found. */
6+
char *raftable_get(int key);
7+
8+
/*
9+
* Adds/updates value by key. Returns when the value gets replicated.
10+
* Storing NULL will delete the item from the table.
11+
*/
12+
void raftable_set(int key, char *value);
13+
14+
/*
15+
* Iterates over all items in the table, calling func(key, value, arg)
16+
* for each of them.
17+
*/
18+
void raftable_every(void (*func)(int, char *, void *), void *arg);
19+
20+
SQL API:
21+
-- set
22+
raftable(key int, value text);
23+
24+
-- get
25+
raftable(key int) returns text;
26+
27+
-- list
28+
raftable() returns table (key int, value text);

‎contrib/raftable/raftable--1.0.sql

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
2+
\echo Use "CREATE EXTENSION raftable" to load this file. \quit
3+
4+
-- get
5+
CREATE FUNCTION raftable(key int)
6+
RETURNS text
7+
AS 'MODULE_PATHNAME','raftable_sql_get'
8+
LANGUAGE C;
9+
10+
-- set
11+
CREATE FUNCTION raftable(key int, value text)
12+
RETURNS void
13+
AS 'MODULE_PATHNAME','raftable_sql_set'
14+
LANGUAGE C;
15+
16+
-- list
17+
CREATE FUNCTION raftable()
18+
RETURNS table (key int, value text)
19+
AS 'MODULE_PATHNAME','raftable_sql_list'
20+
LANGUAGE C;

‎contrib/raftable/raftable.c

Lines changed: 184 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,184 @@
1+
/*
2+
* raftable.c
3+
*
4+
* A key-value table replicated over Raft.
5+
*
6+
*/
7+
8+
#include "postgres.h"
9+
#include "utils/builtins.h"
10+
#include "utils/hsearch.h"
11+
#include "storage/lwlock.h"
12+
#include "storage/ipc.h"
13+
#include "funcapi.h"
14+
#include "access/htup_details.h"
15+
#include "miscadmin.h"
16+
17+
#include "raftable.h"
18+
19+
#define RAFTABLE_SHMEM_SIZE (16 * 1024)
20+
#define RAFTABLE_HASH_SIZE (127)
21+
#define RAFTABLE_VALUE_LEN 64
22+
23+
void _PG_init(void);
24+
void _PG_fini(void);
25+
26+
PG_MODULE_MAGIC;
27+
28+
PG_FUNCTION_INFO_V1(raftable_sql_get);
29+
PG_FUNCTION_INFO_V1(raftable_sql_set);
30+
PG_FUNCTION_INFO_V1(raftable_sql_list);
31+
32+
static HTAB *data;
33+
static LWLockId datalock;
34+
static shmem_startup_hook_type PreviousShmemStartupHook;
35+
36+
typedef struct RaftableEntry
37+
{
38+
int key;
39+
char value[RAFTABLE_VALUE_LEN];
40+
} RaftableEntry;
41+
42+
Datum
43+
raftable_sql_get(PG_FUNCTION_ARGS)
44+
{
45+
RaftableEntry *entry;
46+
int key = PG_GETARG_INT32(0);
47+
48+
LWLockAcquire(datalock, LW_SHARED);
49+
entry = hash_search(data, &key, HASH_FIND, NULL);
50+
51+
if (entry)
52+
{
53+
text *t = cstring_to_text(entry->value);
54+
LWLockRelease(datalock);
55+
PG_RETURN_TEXT_P(t);
56+
}
57+
else
58+
{
59+
LWLockRelease(datalock);
60+
PG_RETURN_NULL();
61+
}
62+
}
63+
64+
Datum
65+
raftable_sql_set(PG_FUNCTION_ARGS)
66+
{
67+
int key = PG_GETARG_INT32(0);
68+
69+
LWLockAcquire(datalock, LW_EXCLUSIVE);
70+
if (PG_ARGISNULL(1))
71+
hash_search(data, &key, HASH_REMOVE, NULL);
72+
else
73+
{
74+
RaftableEntry *entry = hash_search(data, &key, HASH_ENTER, NULL);
75+
entry->key = key;
76+
text_to_cstring_buffer(PG_GETARG_TEXT_P(1), entry->value, sizeof(entry->value));
77+
}
78+
LWLockRelease(datalock);
79+
80+
PG_RETURN_VOID();
81+
}
82+
83+
Datum
84+
raftable_sql_list(PG_FUNCTION_ARGS)
85+
{
86+
FuncCallContext *funcctx;
87+
MemoryContext oldcontext;
88+
HASH_SEQ_STATUS *scan;
89+
RaftableEntry *entry;
90+
91+
if (SRF_IS_FIRSTCALL())
92+
{
93+
TypeFuncClass tfc;
94+
funcctx = SRF_FIRSTCALL_INIT();
95+
96+
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
97+
98+
tfc = get_call_result_type(fcinfo, NULL, &funcctx->tuple_desc);
99+
Assert(tfc == TYPEFUNC_COMPOSITE);
100+
funcctx->tuple_desc = BlessTupleDesc(funcctx->tuple_desc);
101+
102+
scan = (HASH_SEQ_STATUS *)palloc(sizeof(HASH_SEQ_STATUS));
103+
LWLockAcquire(datalock, LW_SHARED);
104+
hash_seq_init(scan, data);
105+
106+
MemoryContextSwitchTo(oldcontext);
107+
108+
funcctx->user_fctx = scan;
109+
}
110+
111+
funcctx = SRF_PERCALL_SETUP();
112+
scan = funcctx->user_fctx;
113+
114+
if ((entry = (RaftableEntry *)hash_seq_search(scan)))
115+
{
116+
HeapTuple tuple;
117+
Datum vals[2];
118+
bool isnull[2];
119+
120+
vals[0] = Int32GetDatum(entry->key);
121+
vals[1] = CStringGetTextDatum(entry->value);
122+
isnull[0] = isnull[1] = false;
123+
124+
tuple = heap_form_tuple(funcctx->tuple_desc, vals, isnull);
125+
SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
126+
}
127+
else
128+
{
129+
LWLockRelease(datalock);
130+
SRF_RETURN_DONE(funcctx);
131+
}
132+
133+
}
134+
135+
static uint32 raftable_hash_fn(const void *key, Size keysize)
136+
{
137+
return (uint32)*(int*)key;
138+
}
139+
140+
static int raftable_match_fn(const void *key1, const void *key2, Size keysize)
141+
{
142+
return *(int*)key1 != *(int*)key2;
143+
}
144+
145+
static void startup_shmem(void)
146+
{
147+
HASHCTL info;
148+
149+
if (PreviousShmemStartupHook){
150+
PreviousShmemStartupHook();
151+
}
152+
153+
datalock = LWLockAssign();
154+
155+
info.keysize = sizeof(int);
156+
info.entrysize = sizeof(RaftableEntry);
157+
info.hash = raftable_hash_fn;
158+
info.match = raftable_match_fn;
159+
160+
data = ShmemInitHash(
161+
"raftable",
162+
RAFTABLE_HASH_SIZE, RAFTABLE_HASH_SIZE,
163+
&info,
164+
HASH_ELEM | HASH_FUNCTION | HASH_COMPARE
165+
);
166+
}
167+
168+
void
169+
_PG_init(void)
170+
{
171+
if (!process_shared_preload_libraries_in_progress)
172+
elog(ERROR, "please add 'raftable' to shared_preload_libraries list");
173+
RequestAddinShmemSpace(RAFTABLE_SHMEM_SIZE);
174+
RequestAddinLWLocks(1);
175+
176+
PreviousShmemStartupHook = shmem_startup_hook;
177+
shmem_startup_hook = startup_shmem;
178+
}
179+
180+
void
181+
_PG_fini(void)
182+
{
183+
shmem_startup_hook = PreviousShmemStartupHook;
184+
}

‎contrib/raftable/raftable.control

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,4 @@
1+
comment = 'Raftable'
2+
default_version = '1.0'
3+
module_pathname = '$libdir/raftable'
4+
relocatable = true

‎contrib/raftable/raftable.h

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
#ifndef __RAFTABLE_H__
2+
#define __RAFTABLE_H__
3+
4+
/* Gets value by key. Returns the value or NULL if not found. */
5+
char *raftable_get(int key);
6+
7+
/*
8+
* Adds/updates value by key. Returns when the value gets replicated.
9+
* Storing NULL will delete the item from the table.
10+
*/
11+
void raftable_set(int key, char *value);
12+
13+
/*
14+
* Iterates over all items in the table, calling func(key, value, arg)
15+
* for each of them.
16+
*/
17+
void raftable_every(void (*func)(int, char *, void *), void *arg);
18+
19+
#endif

0 commit comments

Comments
 (0)
pFad - Phonifier reborn

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.


Alternative Proxies:

Alternative Proxy

pFad Proxy

pFad v3 Proxy

pFad v4 Proxy