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Commitbea3d7e

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Use MemoryContext API for regex memory management.
Previously, regex_t objects' memory was managed with malloc() and free()directly. Switch to palloc()-based memory management instead.Advantages: * memory used by cached regexes is now visible with MemoryContext observability tools * cleanup can be done automatically in certain failure modes (something that later commits will take advantage of) * cleanup can be done in bulkOn the downside, there may be more fragmentation (wasted memory) due toper-regex MemoryContext objects. This is a problem shared with othercached objects in PostgreSQL and can probably be improved with latertuning.Thanks to Noah Misch for suggesting this general approach, whichunblocks later work on interrupts.Suggested-by: Noah Misch <noah@leadboat.com>Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>Discussion:https://postgr.es/m/CA%2BhUKGK3PGKwcKqzoosamn36YW-fsuTdOPPF1i_rtEO%3DnEYKSg%40mail.gmail.com
1 parentfcd77d5 commitbea3d7e

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3 files changed

+45
-20
lines changed

3 files changed

+45
-20
lines changed

‎src/backend/regex/regprefix.c‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -32,7 +32,7 @@ static intfindprefix(struct cnfa *cnfa, struct colormap *cm,
3232
*REG_EXACT: all strings satisfying the regex must match the same string
3333
*or a REG_XXX error code
3434
*
35-
* In the non-failure cases, *string is set to amalloc'd string containing
35+
* In the non-failure cases, *string is set to apalloc'd string containing
3636
* the common prefix or exact value, of length *slength (measured in chrs
3737
* not bytes!).
3838
*

‎src/backend/utils/adt/regexp.c‎

Lines changed: 41 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -96,9 +96,13 @@ typedef struct regexp_matches_ctx
9696
#defineMAX_CACHED_RES32
9797
#endif
9898

99+
/* A parent memory context for regular expressions. */
100+
staticMemoryContextRegexpCacheMemoryContext;
101+
99102
/* this structure describes one cached regular expression */
100103
typedefstructcached_re_str
101104
{
105+
MemoryContextcre_context;/* memory context for this regexp */
102106
char*cre_pat;/* original RE (not null terminated!) */
103107
intcre_pat_len;/* length of original RE, in bytes */
104108
intcre_flags;/* compile flags: extended,icase etc */
@@ -145,6 +149,7 @@ RE_compile_and_cache(text *text_re, int cflags, Oid collation)
145149
intregcomp_result;
146150
cached_re_strre_temp;
147151
charerrMsg[100];
152+
MemoryContextoldcontext;
148153

149154
/*
150155
* Look for a match among previously compiled REs. Since the data
@@ -172,6 +177,13 @@ RE_compile_and_cache(text *text_re, int cflags, Oid collation)
172177
}
173178
}
174179

180+
/* Set up the cache memory on first go through. */
181+
if (unlikely(RegexpCacheMemoryContext==NULL))
182+
RegexpCacheMemoryContext=
183+
AllocSetContextCreate(TopMemoryContext,
184+
"RegexpCacheMemoryContext",
185+
ALLOCSET_SMALL_SIZES);
186+
175187
/*
176188
* Couldn't find it, so try to compile the new RE. To avoid leaking
177189
* resources on failure, we build into the re_temp local.
@@ -183,6 +195,18 @@ RE_compile_and_cache(text *text_re, int cflags, Oid collation)
183195
pattern,
184196
text_re_len);
185197

198+
/*
199+
* Make a memory context for this compiled regexp. This is initially a
200+
* child of the current memory context, so it will be cleaned up
201+
* automatically if compilation is interrupted and throws an ERROR. We'll
202+
* re-parent it under the longer lived cache context if we make it to the
203+
* bottom of this function.
204+
*/
205+
re_temp.cre_context=AllocSetContextCreate(CurrentMemoryContext,
206+
"RegexpMemoryContext",
207+
ALLOCSET_SMALL_SIZES);
208+
oldcontext=MemoryContextSwitchTo(re_temp.cre_context);
209+
186210
regcomp_result=pg_regcomp(&re_temp.cre_re,
187211
pattern,
188212
pattern_len,
@@ -209,21 +233,17 @@ RE_compile_and_cache(text *text_re, int cflags, Oid collation)
209233
errmsg("invalid regular expression: %s",errMsg)));
210234
}
211235

236+
/* Copy the pattern into the per-regexp memory context. */
237+
re_temp.cre_pat=palloc(text_re_len+1);
238+
memcpy(re_temp.cre_pat,text_re_val,text_re_len);
239+
212240
/*
213-
* We use malloc/free for the cre_pat field because the storage has to
214-
* persist across transactions, and because we want to get control back on
215-
* out-of-memory. The Max() is because some malloc implementations return
216-
* NULL for malloc(0).
241+
* NUL-terminate it only for the benefit of the identifier used for the
242+
* memory context, visible in the pg_backend_memory_contexts view.
217243
*/
218-
re_temp.cre_pat=malloc(Max(text_re_len,1));
219-
if (re_temp.cre_pat==NULL)
220-
{
221-
pg_regfree(&re_temp.cre_re);
222-
ereport(ERROR,
223-
(errcode(ERRCODE_OUT_OF_MEMORY),
224-
errmsg("out of memory")));
225-
}
226-
memcpy(re_temp.cre_pat,text_re_val,text_re_len);
244+
re_temp.cre_pat[text_re_len]=0;
245+
MemoryContextSetIdentifier(re_temp.cre_context,re_temp.cre_pat);
246+
227247
re_temp.cre_pat_len=text_re_len;
228248
re_temp.cre_flags=cflags;
229249
re_temp.cre_collation=collation;
@@ -236,16 +256,21 @@ RE_compile_and_cache(text *text_re, int cflags, Oid collation)
236256
{
237257
--num_res;
238258
Assert(num_res<MAX_CACHED_RES);
239-
pg_regfree(&re_array[num_res].cre_re);
240-
free(re_array[num_res].cre_pat);
259+
/* Delete the memory context holding the regexp and pattern. */
260+
MemoryContextDelete(re_array[num_res].cre_context);
241261
}
242262

263+
/* Re-parent the memory context to our long-lived cache context. */
264+
MemoryContextSetParent(re_temp.cre_context,RegexpCacheMemoryContext);
265+
243266
if (num_res>0)
244267
memmove(&re_array[1],&re_array[0],num_res*sizeof(cached_re_str));
245268

246269
re_array[0]=re_temp;
247270
num_res++;
248271

272+
MemoryContextSwitchTo(oldcontext);
273+
249274
return&re_array[0].cre_re;
250275
}
251276

@@ -1990,7 +2015,7 @@ regexp_fixed_prefix(text *text_re, bool case_insensitive, Oid collation,
19902015
slen=pg_wchar2mb_with_len(str,result,slen);
19912016
Assert(slen<maxlen);
19922017

1993-
free(str);
2018+
pfree(str);
19942019

19952020
returnresult;
19962021
}

‎src/include/regex/regcustom.h‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -49,9 +49,9 @@
4949

5050
/* overrides for regguts.h definitions, if any */
5151
#defineFUNCPTR(name,args) (*name) args
52-
#defineMALLOC(n)malloc(n)
53-
#defineFREE(p)free(VS(p))
54-
#defineREALLOC(p,n)realloc(VS(p),n)
52+
#defineMALLOC(n)palloc_extended((n), MCXT_ALLOC_NO_OOM)
53+
#defineFREE(p)pfree(VS(p))
54+
#defineREALLOC(p,n)repalloc_extended(VS(p),(n), MCXT_ALLOC_NO_OOM)
5555
#defineassert(x)Assert(x)
5656

5757
/* internal character type and related */

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