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Commit19f6e9e

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Fix typos, add comments, rename couple of variables
1 parent410aa2d commit19f6e9e

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3 files changed

+134
-57
lines changed

3 files changed

+134
-57
lines changed

‎src/backend/storage/file/cfs.c

Lines changed: 118 additions & 51 deletions
Original file line numberDiff line numberDiff line change
@@ -11,13 +11,16 @@
1111
*
1212
* NOTES:
1313
*
14-
* This fileimplemets compression of file pages.
14+
* This fileimplements compression of file pages.
1515
* Updated compressed pages are always appended to the end of file segment.
16-
* Garbage collector is used to shrink files when them become tool large.
17-
* GC is spawned as one or more background workers. Them recursively traverse all tablespace directories,
18-
* find out *.cfm files are if logical size of the file is twice larger than physical size of the file
19-
* performs compactification. Locking implemented using atomic operations is used to eliminate race
20-
* conditions.
16+
* Garbage collector is used to reclaim storage occupied by outdated versions of pages.
17+
* GC runs one or more background workers which recursively traverse all tablespace
18+
* directories. If worker finds out that logical size of the file is twice as large as
19+
* physical size of the file, it performs compactification.
20+
* To eliminate race conditions, files are locked during compacification.
21+
* Locks are implemented with atomic operations.
22+
*
23+
* TODO Write a note about *.cfm files.
2124
*/
2225

2326
#include"postgres.h"
@@ -51,13 +54,37 @@
5154
#include"utils/resowner_private.h"
5255
#include"postmaster/bgworker.h"
5356

57+
/*
58+
* GUC variable that defines compression level.
59+
* 0 - no compression, 1 - max speed,
60+
* other possible values depend on the specific algorithm.
61+
* Default value is 1.
62+
*/
63+
intcfs_level;
64+
/*
65+
* GUC variable that defines if encryption of compressed pages is enabled.
66+
* Default value is false.
67+
*/
68+
boolcfs_encryption;
69+
/*
70+
* GUC variable - Verify correctness of data written by GC.
71+
* TODO add description and documentation.
72+
*/
73+
boolcfs_gc_verify_file;
74+
75+
/* GUC variable - Number of garbage collection background workers. Default = 1 */
5476
intcfs_gc_workers;
77+
/*
78+
* GUC variable - Specifies the minimum percent of garbage blocks
79+
* needed to trigger a GC of the file. Default = 50
80+
*/
5581
intcfs_gc_threshold;
82+
/* GUC variable - Time to sleep between GC runs in milliseconds. Default = 5000 */
5683
intcfs_gc_period;
84+
/* GUC variable - Delay in milliseconds between files defragmentation. Default = 0
85+
* TODO What is the purpose of this variable?
86+
*/
5787
intcfs_gc_delay;
58-
intcfs_level;
59-
boolcfs_encryption;
60-
boolcfs_gc_verify_file;
6188

6289
staticboolcfs_read_file(intfd,void*data,uint32size);
6390
staticboolcfs_write_file(intfd,voidconst*data,uint32size);
@@ -68,90 +95,109 @@ CfsState* cfs_state;
6895
staticboolcfs_stop;
6996
staticintcfs_processed_segments;
7097

71-
#ifCFS_COMPRESSOR==SNAPPY_COMPRESSOR
7298

73-
#include<snappy-c.h>
99+
/* ----------------------------------------------------------------
100+
*Section 1: Various compression algorithms.
101+
* CFS_COMPRESSOR variable can be set at compile time.
102+
* One should define CFS_COMPRESSOR in cfs.h
103+
* Availiable options are:
104+
* - LZ_COMPRESSOR // FIXME. No actual implementation.
105+
* - ZLIB_COMPRESSOR
106+
* - LZ4_COMPRESSOR
107+
* - SNAPPY_COMPRESSOR
108+
* - LCFSE_COMPRESSOR
109+
* - ZSTD_COMPRESSOR
110+
*
111+
* If none of options is chosen, use standard pglz_compress FIXME?, which is
112+
* slow and non-efficient in comparison with others, but doesn't requre
113+
* any extra libraries.
114+
* ----------------------------------------------------------------
115+
*/
116+
117+
#ifCFS_COMPRESSOR==ZLIB_COMPRESSOR
118+
119+
#include<zlib.h>
74120

75121
size_tcfs_compress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
76122
{
77-
returnsnappy_compress(src,src_size,dst,&dst_size)==SNAPPY_OK ?dst_size :0;
123+
uLongfcompressed_size=dst_size;
124+
intrc=compress2(dst,&compressed_size,src,src_size,cfs_level);
125+
returnrc==Z_OK ?compressed_size :rc;
78126
}
79127

80128
size_tcfs_decompress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
81129
{
82-
returnsnappy_uncompress(src,src_size,dst,&dst_size)==SNAPPY_OK ?dst_size :0;
130+
uLongfdest_len=dst_size;
131+
intrc=uncompress(dst,&dest_len,src,src_size);
132+
returnrc==Z_OK ?dest_len :rc;
83133
}
84134

85135
charconst*cfs_algorithm()
86136
{
87-
return"snappy";
137+
return"zlib";
88138
}
89139

90-
#elifCFS_COMPRESSOR==LCFSE_COMPRESSOR
140+
#elifCFS_COMPRESSOR==LZ4_COMPRESSOR
91141

92-
#include<lcfse.h>
142+
#include<lz4.h>
93143

94144
size_tcfs_compress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
95145
{
96-
char*scratch_buf=palloc(lcfse_encode_scratch_size());
97-
size_trc=lcfse_encode_buffer(dst,dst_size,src,src_size,scratch_buf);
98-
pfree(scratch_buf);
99-
returnrc;
146+
returnLZ4_compress(src,dst,src_size);
100147
}
101148

102149
size_tcfs_decompress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
103150
{
104-
char*scratch_buf=palloc(lcfse_encode_scratch_size());
105-
size_trc=lcfse_decode_buffer(dst,dst_size,src,src_size,scratch_buf);
106-
pfree(scratch_buf);
107-
returnrc;
151+
returnLZ4_decompress_safe(src,dst,src_size,dst_size);
108152
}
109153

110154
charconst*cfs_algorithm()
111155
{
112-
return"lcfse";
156+
return"lz4";
113157
}
114158

115-
#elifCFS_COMPRESSOR==LZ4_COMPRESSOR
159+
#elifCFS_COMPRESSOR==SNAPPY_COMPRESSOR
116160

117-
#include<lz4.h>
161+
#include<snappy-c.h>
118162

119163
size_tcfs_compress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
120164
{
121-
returnLZ4_compress(src,dst,src_size);
165+
returnsnappy_compress(src,src_size,dst,&dst_size)==SNAPPY_OK ?dst_size :0;
122166
}
123167

124168
size_tcfs_decompress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
125169
{
126-
returnLZ4_decompress_safe(src,dst,src_size,dst_size);
170+
returnsnappy_uncompress(src,src_size,dst,&dst_size)==SNAPPY_OK ?dst_size :0;
127171
}
128172

129173
charconst*cfs_algorithm()
130174
{
131-
return"lz4";
175+
return"snappy";
132176
}
133177

134-
#elifCFS_COMPRESSOR==ZLIB_COMPRESSOR
178+
#elifCFS_COMPRESSOR==LCFSE_COMPRESSOR
135179

136-
#include<zlib.h>
180+
#include<lcfse.h>
137181

138182
size_tcfs_compress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
139183
{
140-
uLongfcompressed_size=dst_size;
141-
intrc=compress2(dst,&compressed_size,src,src_size,cfs_level);
142-
returnrc==Z_OK ?compressed_size :rc;
184+
char*scratch_buf=palloc(lcfse_encode_scratch_size());
185+
size_trc=lcfse_encode_buffer(dst,dst_size,src,src_size,scratch_buf);
186+
pfree(scratch_buf);
187+
returnrc;
143188
}
144189

145190
size_tcfs_decompress(void*dst,size_tdst_size,voidconst*src,size_tsrc_size)
146191
{
147-
uLongfdest_len=dst_size;
148-
intrc=uncompress(dst,&dest_len,src,src_size);
149-
returnrc==Z_OK ?dest_len :rc;
192+
char*scratch_buf=palloc(lcfse_encode_scratch_size());
193+
size_trc=lcfse_decode_buffer(dst,dst_size,src,src_size,scratch_buf);
194+
pfree(scratch_buf);
195+
returnrc;
150196
}
151197

152198
charconst*cfs_algorithm()
153199
{
154-
return"zlib";
200+
return"lcfse";
155201
}
156202

157203
#elifCFS_COMPRESSOR==ZSTD_COMPRESSOR
@@ -195,6 +241,15 @@ char const* cfs_algorithm()
195241
#endif
196242

197243

244+
/* ----------------------------------------------------------------
245+
*Section 2: Encryption related functionality.
246+
*
247+
* TODO
248+
* - replace rc4 algrithm with something more appropriate
249+
* - add more comments
250+
* - what does 'offs' variable for?
251+
* ----------------------------------------------------------------
252+
*/
198253
staticvoidcfs_rc4_encrypt_block(void*block,uint32offs,uint32block_size)
199254
{
200255
uint32i;
@@ -205,7 +260,7 @@ static void cfs_rc4_encrypt_block(void* block, uint32 offs, uint32 block_size)
205260
intx=0,y=0;
206261
uint32skip= (offs /BLCKSZ+block_size) %CFS_CIPHER_KEY_SIZE;
207262

208-
memcpy(state,cfs_state->rc4_init_state,CFS_CIPHER_KEY_SIZE);
263+
memcpy(state,cfs_state->cipher_key,CFS_CIPHER_KEY_SIZE);
209264
for (i=0;i<skip;i++) {
210265
x= (x+1) %CFS_CIPHER_KEY_SIZE;
211266
y= (y+state[x]) %CFS_CIPHER_KEY_SIZE;
@@ -224,7 +279,12 @@ static void cfs_rc4_encrypt_block(void* block, uint32 offs, uint32 block_size)
224279
}
225280
}
226281

227-
staticvoidcfs_rc4_init(void)
282+
/*
283+
* Get env variable PG_CIPHER_KEY and initialize encryption state.
284+
* Unset variable afterward.
285+
* Now implements cf4.
286+
*/
287+
staticvoidcfs_encrypt_init(void)
228288
{
229289
intindex1=0;
230290
intindex2=0;
@@ -233,13 +293,13 @@ static void cfs_rc4_init(void)
233293
intkey_length;
234294
intx=0,y=0;
235295
char*cipher_key;
236-
uint8*rc4_init_state=cfs_state->rc4_init_state;
296+
uint8*rc4_init_state=cfs_state->cipher_key;
237297

238298
cipher_key=getenv("PG_CIPHER_KEY");
239299
if (cipher_key==NULL) {
240300
elog(ERROR,"PG_CIPHER_KEY environment variable is not set");
241301
}
242-
unsetenv("PG_CIPHER_KEY");/*make it not possible to inspectthis environment variable through plperl */
302+
unsetenv("PG_CIPHER_KEY");/*disable inspection ofthis environment variable */
243303
key_length=strlen(cipher_key);
244304
for (i=0;i<CFS_CIPHER_KEY_SIZE;++i) {
245305
rc4_init_state[i]= (uint8)i;
@@ -263,20 +323,21 @@ static void cfs_rc4_init(void)
263323
voidcfs_encrypt(void*block,uint32offs,uint32size)
264324
{
265325
if (cfs_encryption)
266-
{
267326
cfs_rc4_encrypt_block(block,offs,size);
268-
}
269327
}
270328

271329
voidcfs_decrypt(void*block,uint32offs,uint32size)
272330
{
273331
if (cfs_encryption)
274-
{
275332
cfs_rc4_encrypt_block(block,offs,size);
276-
}
277333
}
278334

279-
335+
/* ----------------------------------------------------------------
336+
*Section 3: Compression implementation.
337+
*
338+
* TODO add description
339+
* ----------------------------------------------------------------
340+
*/
280341
voidcfs_initialize()
281342
{
282343
cfs_state= (CfsState*)ShmemAlloc(sizeof(CfsState));
@@ -287,9 +348,9 @@ void cfs_initialize()
287348
cfs_state->gc_enabled= true;
288349
cfs_state->max_iterations=0;
289350

290-
if (cfs_encryption) {
291-
cfs_rc4_init();
292-
}
351+
if (cfs_encryption)
352+
cfs_encrypt_init();
353+
293354
elog(LOG,"Start CFS version %s compression algorithm %s encryption %s",
294355
CFS_VERSION,cfs_algorithm(),cfs_encryption ?"enabled" :"disabled");
295356
}
@@ -463,6 +524,12 @@ static int cfs_cmp_page_offs(void const* p1, void const* p2)
463524
returno1<o2 ?-1 :o1==o2 ?0 :1;
464525
}
465526

527+
/* ----------------------------------------------------------------
528+
*Section 4: Garbage collection functionality.
529+
*
530+
* TODO add description. reorder functions.
531+
* ----------------------------------------------------------------
532+
*/
466533
/*
467534
* Perform garbage collection (if required) of file
468535
* @param map_path path to file map file (*.cfm).

‎src/backend/utils/misc/guc.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2825,7 +2825,7 @@ static struct config_int ConfigureNamesInt[] =
28252825

28262826
{
28272827
{"cfs_gc_threshold",PGC_USERSET,UNGROUPED,
2828-
gettext_noop("Percentof garbage in fileafter file is comactified"),
2828+
gettext_noop("Minimum percentof garbageblocksinthefileprior to garbage collection"),
28292829
NULL,
28302830
0
28312831
},
@@ -2837,7 +2837,7 @@ static struct config_int ConfigureNamesInt[] =
28372837

28382838
{
28392839
{"cfs_gc_period",PGC_USERSET,UNGROUPED,
2840-
gettext_noop("Interval in milliseconds betweenCFS garbage collection iterations"),
2840+
gettext_noop("Time to sleep betweenGC runs in milliseconds"),
28412841
NULL,
28422842
GUC_UNIT_MS
28432843
},

‎src/include/storage/cfs.h

Lines changed: 14 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -17,17 +17,25 @@
1717
#defineCFS_MAX_COMPRESSED_SIZE(size) ((size)*2)
1818
#defineCFS_MIN_COMPRESSED_SIZE(size) ((size)*2/3)
1919

20+
/*
21+
* FIXME
22+
*/
2023
#defineLZ_COMPRESSOR 1
2124
#defineZLIB_COMPRESSOR 2
2225
#defineLZ4_COMPRESSOR 3
2326
#defineSNAPPY_COMPRESSOR 4
2427
#defineLCFSE_COMPRESSOR 5
2528
#defineZSTD_COMPRESSOR 6
2629

30+
/*
31+
* Set CFS_COMPRESSOR to one of the names above
32+
* to compile postgres with chosen compression algorithm
33+
*/
2734
#ifndefCFS_COMPRESSOR
2835
#defineCFS_COMPRESSOR ZLIB_COMPRESSOR
2936
#endif
3037

38+
/* Encryption related variables*/
3139
#defineCFS_RC4_DROP_N 3072
3240
#defineCFS_CIPHER_KEY_SIZE 256
3341

@@ -54,6 +62,7 @@ typedef struct
5462
uint64processedBytes;
5563
}CfsStatistic;
5664

65+
/* TODO Add comments */
5766
typedefstruct
5867
{
5968
pg_atomic_flaggc_started;
@@ -62,7 +71,7 @@ typedef struct
6271
intmax_iterations;
6372
boolgc_enabled;
6473
CfsStatisticgc_stat;
65-
uint8rc4_init_state[CFS_CIPHER_KEY_SIZE];
74+
uint8cipher_key[CFS_CIPHER_KEY_SIZE];/* FIXME Is it the key itself? Or some modification?*/
6675
}CfsState;
6776

6877
typedefstruct
@@ -91,13 +100,14 @@ void cfs_decrypt(void* block, uint32 offs, uint32 size);
91100

92101
externCfsState*cfs_state;
93102

103+
externintcfs_level;
104+
externboolcfs_encryption;
105+
externboolcfs_gc_verify_file;
106+
94107
externintcfs_gc_delay;
95108
externintcfs_gc_period;
96109
externintcfs_gc_workers;
97110
externintcfs_gc_threshold;
98-
externintcfs_level;
99-
externboolcfs_gc_verify_file;
100-
externboolcfs_encryption;
101111
#endif
102112

103113

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