Re: Protect syscache from bloating with negative cache entries - Mailing list pgsql-hackers
| From | Kyotaro HORIGUCHI |
|---|---|
| Subject | Re: Protect syscache from bloating with negative cache entries |
| Date | |
| Msg-id | 20180315.141246.130742928.horiguchi.kyotaro@lab.ntt.co.jp Whole thread Raw |
| In response to | Re: Protect syscache from bloating with negative cache entries (Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>) |
| Responses |
Re: Re: Protect syscache from bloating with negative cache entries
(David Steele <david@pgmasters.net>)
Re: Protect syscache from bloating with negative cache entries (Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>) |
| List | pgsql-hackers |
At Mon, 12 Mar 2018 17:34:08 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote in
<20180312.173408.162882093.horiguchi.kyotaro@lab.ntt.co.jp>
> > > In short, it's not really apparent to me that negative syscache entries
> > > are the major problem of this kind. I'm afraid that you're drawing very
> > > large conclusions from a specific workload. Maybe we could fix that
> > > workload some other way.
> >
> > The current patch doesn't consider whether an entry is negative
> > or positive(?). Just clean up all entries based on time.
> >
> > If relation has to have the same characterictics to syscaches, it
> > might be better be on the catcache mechanism, instaed of adding
> > the same pruning mechanism to dynahash..
>
> For the moment, I added such feature to dynahash and let only
> relcache use it in this patch. Hash element has different shape
> in "prunable" hash and pruning is performed in a similar way
> sharing the setting with syscache. This seems working fine.
I gave consideration on plancache. The most different
characteristics from catcache and relcache is the fact that it is
not voluntarily removable since CachedPlanSource, the root struct
of a plan cache, holds some indispensable inforamtion. In regards
to prepared queries, even if we store the information into
another location, for example in "Prepred Queries" hash, it
merely moving a big data into another place.
Looking into CachedPlanSoruce, generic plan is a part that is
safely removable since it is rebuilt as necessary. Keeping "old"
plancache entries not holding a generic plan can reduce memory
usage.
For testing purpose, I made 50000 parepared statement like
"select sum(c) from p where e < $" on 100 partitions,
With disabling the feature (0004 patch) VSZ of the backend
exceeds 3GB (It is still increasing at the moment), while it
stops to increase at about 997MB for min_cached_plans = 1000 and
plancache_prune_min_age = '10s'.
# 10s is apparently short for acutual use, of course.
It is expected to be significant amount if the plan is large
enough but I'm still not sure it is worth doing, or is a right
way.
The attached is the patch set including this plancache stuff.
0001- catcache time-based expiration (The origin of this thread)
0002- introduces dynahash pruning feature
0003- implement relcache pruning using 0002
0004- (perhaps) independent from the three above. PoC of
plancache pruning. Details are shown above.
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
From 705b67a79ef7e27a450083944f8d970b7eb9e619 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Tue, 26 Dec 2017 17:43:09 +0900
Subject: [PATCH 1/4] Remove entries that haven't been used for a certain time
Catcache entries can be left alone for several reasons. It is not
desirable that they eat up memory. With this patch, This adds
consideration of removal of entries that haven't been used for a
certain time before enlarging the hash array.
---
doc/src/sgml/config.sgml | 38 +++++++
src/backend/access/transam/xact.c | 3 +
src/backend/utils/cache/catcache.c | 152 +++++++++++++++++++++++++-
src/backend/utils/misc/guc.c | 23 ++++
src/backend/utils/misc/postgresql.conf.sample | 2 +
src/include/utils/catcache.h | 19 ++++
6 files changed, 233 insertions(+), 4 deletions(-)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 3a8fc7d803..394e0703f8 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1557,6 +1557,44 @@ include_dir 'conf.d'
</listitem>
</varlistentry>
+ <varlistentry id="guc-syscache-memory-target" xreflabel="syscache_memory_target">
+ <term><varname>syscache_memory_target</varname> (<type>integer</type>)
+ <indexterm>
+ <primary><varname>syscache_memory_target</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Specifies the maximum amount of memory to which syscache is expanded
+ without pruning. The value defaults to 0, indicating that pruning is
+ always considered. After exceeding this size, syscache pruning is
+ considered according to
+ <xref linkend="guc-syscache-prune-min-age"/>. If you need to keep
+ certain amount of syscache entries with intermittent usage, try
+ increase this setting.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="guc-syscache-prune-min-age" xreflabel="syscache_prune_min_age">
+ <term><varname>syscache_prune_min_age</varname> (<type>integer</type>)
+ <indexterm>
+ <primary><varname>syscache_prune_min_age</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Specifies the minimum amount of unused time in seconds at which a
+ syscache entry is considered to be removed. -1 indicates that syscache
+ pruning is disabled at all. The value defaults to 600 seconds
+ (<literal>10 minutes</literal>). The syscache entries that are not
+ used for the duration can be removed to prevent syscache bloat. This
+ behavior is suppressed until the size of syscache exceeds
+ <xref linkend="guc-syscache-memory-target"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-max-stack-depth" xreflabel="max_stack_depth">
<term><varname>max_stack_depth</varname> (<type>integer</type>)
<indexterm>
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index dbaaf8e005..86d76917bb 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -733,6 +733,9 @@ void
SetCurrentStatementStartTimestamp(void)
{
stmtStartTimestamp = GetCurrentTimestamp();
+
+ /* Set this timestamp as aproximated current time */
+ SetCatCacheClock(stmtStartTimestamp);
}
/*
diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c
index 5ddbf6eab1..0236a05127 100644
--- a/src/backend/utils/cache/catcache.c
+++ b/src/backend/utils/cache/catcache.c
@@ -71,9 +71,23 @@
#define CACHE6_elog(a,b,c,d,e,f,g)
#endif
+/*
+ * GUC variable to define the minimum size of hash to cosider entry eviction.
+ * Let the name be the same with the guc variable name, not using 'catcache'.
+ */
+int syscache_memory_target = 0;
+
+/* GUC variable to define the minimum age of entries that will be cosidered
+ * to be evicted in seconds. Ditto for the name.
+ */
+int syscache_prune_min_age = 600;
+
/* Cache management header --- pointer is NULL until created */
static CatCacheHeader *CacheHdr = NULL;
+/* Timestamp used for any operation on caches. */
+TimestampTz catcacheclock = 0;
+
static inline HeapTuple SearchCatCacheInternal(CatCache *cache,
int nkeys,
Datum v1, Datum v2,
@@ -866,9 +880,130 @@ InitCatCache(int id,
*/
MemoryContextSwitchTo(oldcxt);
+ /* initilize catcache reference clock if haven't done yet */
+ if (catcacheclock == 0)
+ catcacheclock = GetCurrentTimestamp();
+
return cp;
}
+/*
+ * CatCacheCleanupOldEntries - Remove infrequently-used entries
+ *
+ * Catcache entries can be left alone for several reasons. We remove them if
+ * they not accessed for a certain time to prevent catcache from bloating. The
+ * eviction is performed with the similar algorithm with buffer eviction using
+ * access counter. Entries that are accessed several times can live longer
+ * than those that have had no access in the same duration.
+ */
+static bool
+CatCacheCleanupOldEntries(CatCache *cp)
+{
+ int i;
+ int nremoved = 0;
+ size_t hash_size;
+#ifdef CATCACHE_STATS
+ /* These variables are only for debugging purpose */
+ int ntotal = 0;
+ /*
+ * nth element in nentries stores the number of cache entries that have
+ * lived unaccessed for corresponding multiple in ageclass of
+ * syscache_prune_min_age. The index of nremoved_entry is the value of the
+ * clock-sweep counter, which takes from 0 up to 2.
+ */
+ double ageclass[] = {0.05, 0.1, 1.0, 2.0, 3.0, 0.0};
+ int nentries[] = {0, 0, 0, 0, 0, 0};
+ int nremoved_entry[3] = {0, 0, 0};
+ int j;
+#endif
+
+ /* Return immediately if no pruning is wanted */
+ if (syscache_prune_min_age < 0)
+ return false;
+
+ /*
+ * Return without pruning if the size of the hash is below the target.
+ * Since the area for bucket array is dominant, consider only it.
+ */
+ hash_size = cp->cc_nbuckets * sizeof(dlist_head);
+ if (hash_size < (Size) syscache_memory_target * 1024L)
+ return false;
+
+ /* Search the whole hash for entries to remove */
+ for (i = 0; i < cp->cc_nbuckets; i++)
+ {
+ dlist_mutable_iter iter;
+
+ dlist_foreach_modify(iter, &cp->cc_bucket[i])
+ {
+ CatCTup *ct = dlist_container(CatCTup, cache_elem, iter.cur);
+ long entry_age;
+ int us;
+
+
+ /*
+ * Calculate the duration from the time of the last access to the
+ * "current" time. Since catcacheclock is not advanced within a
+ * transaction, the entries that are accessed within the current
+ * transaction won't be pruned.
+ */
+ TimestampDifference(ct->lastaccess, catcacheclock, &entry_age, &us);
+
+#ifdef CATCACHE_STATS
+ /* count catcache entries for each age class */
+ ntotal++;
+ for (j = 0 ;
+ ageclass[j] != 0.0 &&
+ entry_age > syscache_prune_min_age * ageclass[j] ;
+ j++);
+ if (ageclass[j] == 0.0) j--;
+ nentries[j]++;
+#endif
+
+ /*
+ * Try to remove entries older than syscache_prune_min_age
+ * seconds. Entries that are not accessed after last pruning are
+ * removed in that seconds, and that has been accessed several
+ * times are removed after leaving alone for up to three times of
+ * the duration. We don't try shrink buckets since pruning
+ * effectively caps catcache expansion in the long term.
+ */
+ if (entry_age > syscache_prune_min_age)
+ {
+#ifdef CATCACHE_STATS
+ Assert (ct->naccess >= 0 && ct->naccess <= 2);
+ nremoved_entry[ct->naccess]++;
+#endif
+ if (ct->naccess > 0)
+ ct->naccess--;
+ else
+ {
+ if (!ct->c_list || ct->c_list->refcount == 0)
+ {
+ CatCacheRemoveCTup(cp, ct);
+ nremoved++;
+ }
+ }
+ }
+ }
+ }
+
+#ifdef CATCACHE_STATS
+ ereport(DEBUG1,
+ (errmsg ("removed %d/%d, age(-%.0fs:%d, -%.0fs:%d, *-%.0fs:%d, -%.0fs:%d, -%.0fs:%d) naccessed(0:%d, 1:%d,
2:%d)",
+ nremoved, ntotal,
+ ageclass[0] * syscache_prune_min_age, nentries[0],
+ ageclass[1] * syscache_prune_min_age, nentries[1],
+ ageclass[2] * syscache_prune_min_age, nentries[2],
+ ageclass[3] * syscache_prune_min_age, nentries[3],
+ ageclass[4] * syscache_prune_min_age, nentries[4],
+ nremoved_entry[0], nremoved_entry[1], nremoved_entry[2]),
+ errhidestmt(true)));
+#endif
+
+ return nremoved > 0;
+}
+
/*
* Enlarge a catcache, doubling the number of buckets.
*/
@@ -1282,6 +1417,11 @@ SearchCatCacheInternal(CatCache *cache,
*/
dlist_move_head(bucket, &ct->cache_elem);
+ /* Update access information for pruning */
+ if (ct->naccess < 2)
+ ct->naccess++;
+ ct->lastaccess = catcacheclock;
+
/*
* If it's a positive entry, bump its refcount and return it. If it's
* negative, we can report failure to the caller.
@@ -1813,7 +1953,6 @@ ReleaseCatCacheList(CatCList *list)
CatCacheRemoveCList(list->my_cache, list);
}
-
/*
* CatalogCacheCreateEntry
* Create a new CatCTup entry, copying the given HeapTuple and other
@@ -1906,6 +2045,8 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp, Datum *arguments,
ct->dead = false;
ct->negative = negative;
ct->hash_value = hashValue;
+ ct->naccess = 0;
+ ct->lastaccess = catcacheclock;
dlist_push_head(&cache->cc_bucket[hashIndex], &ct->cache_elem);
@@ -1913,10 +2054,13 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp, Datum *arguments,
CacheHdr->ch_ntup++;
/*
- * If the hash table has become too full, enlarge the buckets array. Quite
- * arbitrarily, we enlarge when fill factor > 2.
+ * If the hash table has become too full, try cleanup by removing
+ * infrequently used entries to make a room for the new entry. If it
+ * failed, enlarge the bucket array instead. Quite arbitrarily, we try
+ * this when fill factor > 2.
*/
- if (cache->cc_ntup > cache->cc_nbuckets * 2)
+ if (cache->cc_ntup > cache->cc_nbuckets * 2 &&
+ !CatCacheCleanupOldEntries(cache))
RehashCatCache(cache);
return ct;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index a4f9b3668e..5e0d18657f 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -78,6 +78,7 @@
#include "tsearch/ts_cache.h"
#include "utils/builtins.h"
#include "utils/bytea.h"
+#include "utils/catcache.h"
#include "utils/guc_tables.h"
#include "utils/memutils.h"
#include "utils/pg_locale.h"
@@ -1972,6 +1973,28 @@ static struct config_int ConfigureNamesInt[] =
NULL, NULL, NULL
},
+ {
+ {"syscache_memory_target", PGC_USERSET, RESOURCES_MEM,
+ gettext_noop("Sets the minimum syscache size to keep."),
+ gettext_noop("Syscache is not pruned before exceeding this size."),
+ GUC_UNIT_KB
+ },
+ &syscache_memory_target,
+ 0, 0, MAX_KILOBYTES,
+ NULL, NULL, NULL
+ },
+
+ {
+ {"syscache_prune_min_age", PGC_USERSET, RESOURCES_MEM,
+ gettext_noop("Sets the minimum duration of an unused syscache entry to remove."),
+ gettext_noop("Syscache entries that live unused for longer than this seconds are considered to be
removed."),
+ GUC_UNIT_S
+ },
+ &syscache_prune_min_age,
+ 600, -1, INT_MAX,
+ NULL, NULL, NULL
+ },
+
/*
* We use the hopefully-safely-small value of 100kB as the compiled-in
* default for max_stack_depth. InitializeGUCOptions will increase it if
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 39272925fb..5a5729a88f 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -124,6 +124,8 @@
#work_mem = 4MB # min 64kB
#maintenance_work_mem = 64MB # min 1MB
#autovacuum_work_mem = -1 # min 1MB, or -1 to use maintenance_work_mem
+#syscache_memory_target = 0kB # in kB. zero disables the feature
+#syscache_prune_min_age = 600s # -1 disables the feature
#max_stack_depth = 2MB # min 100kB
#dynamic_shared_memory_type = posix # the default is the first option
# supported by the operating system:
diff --git a/src/include/utils/catcache.h b/src/include/utils/catcache.h
index 7b22f9c7bc..c3c4d65998 100644
--- a/src/include/utils/catcache.h
+++ b/src/include/utils/catcache.h
@@ -22,6 +22,7 @@
#include "access/htup.h"
#include "access/skey.h"
+#include "datatype/timestamp.h"
#include "lib/ilist.h"
#include "utils/relcache.h"
@@ -119,6 +120,8 @@ typedef struct catctup
bool dead; /* dead but not yet removed? */
bool negative; /* negative cache entry? */
HeapTupleData tuple; /* tuple management header */
+ int naccess; /* # of access to this entry, up to 2 */
+ TimestampTz lastaccess; /* approx. timestamp of the last usage */
/*
* The tuple may also be a member of at most one CatCList. (If a single
@@ -189,6 +192,22 @@ typedef struct catcacheheader
/* this extern duplicates utils/memutils.h... */
extern PGDLLIMPORT MemoryContext CacheMemoryContext;
+/* for guc.c, not PGDLLPMPORT'ed */
+extern int syscache_prune_min_age;
+extern int syscache_memory_target;
+
+/* to use as access timestamp of catcache entries */
+extern TimestampTz catcacheclock;
+
+/*
+ * SetCatCacheClock - set timestamp for catcache access record
+ */
+static inline void
+SetCatCacheClock(TimestampTz ts)
+{
+ catcacheclock = ts;
+}
+
extern void CreateCacheMemoryContext(void);
extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
--
2.16.2
From 037f3534f5274eb7bcdb5adee262b5af624175e2 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Mon, 12 Mar 2018 15:52:18 +0900
Subject: [PATCH 2/4] introduce dynhash pruning
---
src/backend/utils/hash/dynahash.c | 169 +++++++++++++++++++++++++++++++++-----
src/include/utils/catcache.h | 12 +++
src/include/utils/hsearch.h | 21 ++++-
3 files changed, 182 insertions(+), 20 deletions(-)
diff --git a/src/backend/utils/hash/dynahash.c b/src/backend/utils/hash/dynahash.c
index 5281cd5410..a5b4979662 100644
--- a/src/backend/utils/hash/dynahash.c
+++ b/src/backend/utils/hash/dynahash.c
@@ -88,6 +88,7 @@
#include "access/xact.h"
#include "storage/shmem.h"
#include "storage/spin.h"
+#include "utils/catcache.h"
#include "utils/dynahash.h"
#include "utils/memutils.h"
@@ -184,6 +185,10 @@ struct HASHHDR
long ssize; /* segment size --- must be power of 2 */
int sshift; /* segment shift = log2(ssize) */
int nelem_alloc; /* number of entries to allocate at once */
+ bool prunable; /* true if prunable */
+ HASH_PRUNE_CB prune_cb; /* pruning callback. see above. */
+ int *memory_target; /* pointer to memory target */
+ int *prune_min_age; /* pointer to prune minimum age */
#ifdef HASH_STATISTICS
@@ -227,16 +232,18 @@ struct HTAB
int sshift; /* segment shift = log2(ssize) */
};
+#define HASHELEMENT_SIZE(ctlp) MAXALIGN(ctlp->prunable ? sizeof(PRUNABLE_HASHELEMENT) : sizeof(HASHELEMENT))
+
/*
* Key (also entry) part of a HASHELEMENT
*/
-#define ELEMENTKEY(helem) (((char *)(helem)) + MAXALIGN(sizeof(HASHELEMENT)))
+#define ELEMENTKEY(helem, ctlp) (((char *)(helem)) + HASHELEMENT_SIZE(ctlp))
/*
* Obtain element pointer given pointer to key
*/
-#define ELEMENT_FROM_KEY(key) \
- ((HASHELEMENT *) (((char *) (key)) - MAXALIGN(sizeof(HASHELEMENT))))
+#define ELEMENT_FROM_KEY(key, ctlp) \
+ ((HASHELEMENT *) (((char *) (key)) - HASHELEMENT_SIZE(ctlp)))
/*
* Fast MOD arithmetic, assuming that y is a power of 2 !
@@ -257,6 +264,7 @@ static HASHSEGMENT seg_alloc(HTAB *hashp);
static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx);
static bool dir_realloc(HTAB *hashp);
static bool expand_table(HTAB *hashp);
+static bool prune_entries(HTAB *hashp);
static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx);
static void hdefault(HTAB *hashp);
static int choose_nelem_alloc(Size entrysize);
@@ -497,6 +505,25 @@ hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
hctl->entrysize = info->entrysize;
}
+ /*
+ * hash table runs pruning
+ */
+ if (flags & HASH_PRUNABLE)
+ {
+ hctl->prunable = true;
+ hctl->prune_cb = info->prune_cb;
+ if (info->memory_target)
+ hctl->memory_target = info->memory_target;
+ else
+ hctl->memory_target = &syscache_memory_target;
+ if (info->prune_min_age)
+ hctl->prune_min_age = info->prune_min_age;
+ else
+ hctl->prune_min_age = &syscache_prune_min_age;
+ }
+ else
+ hctl->prunable = false;
+
/* make local copies of heavily-used constant fields */
hashp->keysize = hctl->keysize;
hashp->ssize = hctl->ssize;
@@ -982,7 +1009,7 @@ hash_search_with_hash_value(HTAB *hashp,
while (currBucket != NULL)
{
if (currBucket->hashvalue == hashvalue &&
- match(ELEMENTKEY(currBucket), keyPtr, keysize) == 0)
+ match(ELEMENTKEY(currBucket, hctl), keyPtr, keysize) == 0)
break;
prevBucketPtr = &(currBucket->link);
currBucket = *prevBucketPtr;
@@ -995,6 +1022,17 @@ hash_search_with_hash_value(HTAB *hashp,
if (foundPtr)
*foundPtr = (bool) (currBucket != NULL);
+ /* Update access counter if needed */
+ if (hctl->prunable && currBucket &&
+ (action == HASH_FIND || action == HASH_ENTER))
+ {
+ PRUNABLE_HASHELEMENT *prunable_elm =
+ (PRUNABLE_HASHELEMENT *) currBucket;
+ if (prunable_elm->naccess < 2)
+ prunable_elm->naccess++;
+ prunable_elm->last_access = GetCatCacheClock();
+ }
+
/*
* OK, now what?
*/
@@ -1002,7 +1040,8 @@ hash_search_with_hash_value(HTAB *hashp,
{
case HASH_FIND:
if (currBucket != NULL)
- return (void *) ELEMENTKEY(currBucket);
+ return (void *) ELEMENTKEY(currBucket, hctl);
+
return NULL;
case HASH_REMOVE:
@@ -1031,7 +1070,7 @@ hash_search_with_hash_value(HTAB *hashp,
* element, because someone else is going to reuse it the next
* time something is added to the table
*/
- return (void *) ELEMENTKEY(currBucket);
+ return (void *) ELEMENTKEY(currBucket, hctl);
}
return NULL;
@@ -1043,7 +1082,7 @@ hash_search_with_hash_value(HTAB *hashp,
case HASH_ENTER:
/* Return existing element if found, else create one */
if (currBucket != NULL)
- return (void *) ELEMENTKEY(currBucket);
+ return (void *) ELEMENTKEY(currBucket, hctl);
/* disallow inserts if frozen */
if (hashp->frozen)
@@ -1073,8 +1112,18 @@ hash_search_with_hash_value(HTAB *hashp,
/* copy key into record */
currBucket->hashvalue = hashvalue;
- hashp->keycopy(ELEMENTKEY(currBucket), keyPtr, keysize);
+ hashp->keycopy(ELEMENTKEY(currBucket, hctl), keyPtr, keysize);
+ /* set access counter */
+ if (hctl->prunable)
+ {
+ PRUNABLE_HASHELEMENT *prunable_elm =
+ (PRUNABLE_HASHELEMENT *) currBucket;
+ if (prunable_elm->naccess < 2)
+ prunable_elm->naccess++;
+ prunable_elm->last_access = GetCatCacheClock();
+ }
+
/*
* Caller is expected to fill the data field on return. DO NOT
* insert any code that could possibly throw error here, as doing
@@ -1082,7 +1131,7 @@ hash_search_with_hash_value(HTAB *hashp,
* caller's data structure.
*/
- return (void *) ELEMENTKEY(currBucket);
+ return (void *) ELEMENTKEY(currBucket, hctl);
}
elog(ERROR, "unrecognized hash action code: %d", (int) action);
@@ -1114,7 +1163,7 @@ hash_update_hash_key(HTAB *hashp,
void *existingEntry,
const void *newKeyPtr)
{
- HASHELEMENT *existingElement = ELEMENT_FROM_KEY(existingEntry);
+ HASHELEMENT *existingElement = ELEMENT_FROM_KEY(existingEntry, hashp->hctl);
HASHHDR *hctl = hashp->hctl;
uint32 newhashvalue;
Size keysize;
@@ -1198,7 +1247,7 @@ hash_update_hash_key(HTAB *hashp,
while (currBucket != NULL)
{
if (currBucket->hashvalue == newhashvalue &&
- match(ELEMENTKEY(currBucket), newKeyPtr, keysize) == 0)
+ match(ELEMENTKEY(currBucket, hctl), newKeyPtr, keysize) == 0)
break;
prevBucketPtr = &(currBucket->link);
currBucket = *prevBucketPtr;
@@ -1232,7 +1281,7 @@ hash_update_hash_key(HTAB *hashp,
/* copy new key into record */
currBucket->hashvalue = newhashvalue;
- hashp->keycopy(ELEMENTKEY(currBucket), newKeyPtr, keysize);
+ hashp->keycopy(ELEMENTKEY(currBucket, hctl), newKeyPtr, keysize);
/* rest of record is untouched */
@@ -1386,8 +1435,8 @@ hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp)
void *
hash_seq_search(HASH_SEQ_STATUS *status)
{
- HTAB *hashp;
- HASHHDR *hctl;
+ HTAB *hashp = status->hashp;
+ HASHHDR *hctl = hashp->hctl;
uint32 max_bucket;
long ssize;
long segment_num;
@@ -1402,15 +1451,13 @@ hash_seq_search(HASH_SEQ_STATUS *status)
status->curEntry = curElem->link;
if (status->curEntry == NULL) /* end of this bucket */
++status->curBucket;
- return (void *) ELEMENTKEY(curElem);
+ return (void *) ELEMENTKEY(curElem, hctl);
}
/*
* Search for next nonempty bucket starting at curBucket.
*/
curBucket = status->curBucket;
- hashp = status->hashp;
- hctl = hashp->hctl;
ssize = hashp->ssize;
max_bucket = hctl->max_bucket;
@@ -1456,7 +1503,7 @@ hash_seq_search(HASH_SEQ_STATUS *status)
if (status->curEntry == NULL) /* end of this bucket */
++curBucket;
status->curBucket = curBucket;
- return (void *) ELEMENTKEY(curElem);
+ return (void *) ELEMENTKEY(curElem, hctl);
}
void
@@ -1550,6 +1597,10 @@ expand_table(HTAB *hashp)
*/
if ((uint32) new_bucket > hctl->high_mask)
{
+ /* try pruning before expansion. return true on success */
+ if (hctl->prunable && prune_entries(hashp))
+ return true;
+
hctl->low_mask = hctl->high_mask;
hctl->high_mask = (uint32) new_bucket | hctl->low_mask;
}
@@ -1592,6 +1643,86 @@ expand_table(HTAB *hashp)
return true;
}
+static bool
+prune_entries(HTAB *hashp)
+{
+ HASHHDR *hctl = hashp->hctl;
+ HASH_SEQ_STATUS status;
+ void *elm;
+ TimestampTz currclock = GetCatCacheClock();
+ int nall = 0,
+ nremoved = 0;
+
+ Assert(hctl->prunable);
+
+ /* not called for frozen or under seqscan. see
+ * hash_search_with_hash_value. */
+ Assert(IS_PARTITIONED(hctl) ||
+ hashp->frozen ||
+ hctl->freeList[0].nentries / (long) (hctl->max_bucket + 1) <
+ hctl->ffactor ||
+ has_seq_scans(hashp));
+
+ /* This setting prevents pruning */
+ if (*hctl->prune_min_age < 0)
+ return false;
+
+ /*
+ * return false immediately if this hash is small enough. We only consider
+ * bucket array size since it is the significant part of memory usage.
+ * settings is shared with syscache
+ */
+ if (hctl->dsize * sizeof(HASHBUCKET) * hashp->ssize <
+ (Size) *hctl->memory_target * 1024L)
+ return false;
+
+ /*
+ * Ok, this hash can be pruned. start pruning. This function is called
+ * early enough for doing this via public API.
+ */
+ hash_seq_init(&status, hashp);
+ while ((elm = hash_seq_search(&status)) != NULL)
+ {
+ PRUNABLE_HASHELEMENT *helm =
+ (PRUNABLE_HASHELEMENT *)ELEMENT_FROM_KEY(elm, hctl);
+ long entry_age;
+ int us;
+
+ nall++;
+
+ TimestampDifference(helm->last_access, currclock, &entry_age, &us);
+
+ /* settings is shared with syscache */
+ if (entry_age > *hctl->prune_min_age)
+ {
+ /* Wait for the next chance if this is recently used */
+ if (helm->naccess > 0)
+ helm->naccess--;
+ else
+ {
+ /* just call it if callback is provided, remove otherwise */
+ if (hctl->prune_cb)
+ {
+ if (hctl->prune_cb(hashp, (void *)elm))
+ nremoved++;
+ }
+ else
+ {
+ bool found;
+
+ hash_search(hashp, elm, HASH_REMOVE, &found);
+ Assert(found);
+ nremoved++;
+ }
+ }
+ }
+ }
+
+ elog(DEBUG1, "removed %d/%d entries from hash \"%s\"",
+ nremoved, nall, hashp->tabname);
+
+ return nremoved > 0;
+}
static bool
dir_realloc(HTAB *hashp)
@@ -1665,7 +1796,7 @@ element_alloc(HTAB *hashp, int nelem, int freelist_idx)
return false;
/* Each element has a HASHELEMENT header plus user data. */
- elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(hctl->entrysize);
+ elementSize = HASHELEMENT_SIZE(hctl) + MAXALIGN(hctl->entrysize);
CurrentDynaHashCxt = hashp->hcxt;
firstElement = (HASHELEMENT *) hashp->alloc(nelem * elementSize);
diff --git a/src/include/utils/catcache.h b/src/include/utils/catcache.h
index c3c4d65998..fcc680bb82 100644
--- a/src/include/utils/catcache.h
+++ b/src/include/utils/catcache.h
@@ -208,6 +208,18 @@ SetCatCacheClock(TimestampTz ts)
catcacheclock = ts;
}
+/*
+ * GetCatCacheClock - get timestamp for catcache access record
+ *
+ * This clock is basically provided for catcache usage, but dynahash has a
+ * similar pruning mechanism and wants to use the same clock.
+ */
+static inline TimestampTz
+GetCatCacheClock(void)
+{
+ return catcacheclock;
+}
+
extern void CreateCacheMemoryContext(void);
extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
diff --git a/src/include/utils/hsearch.h b/src/include/utils/hsearch.h
index 8357faac5a..7ea3c75423 100644
--- a/src/include/utils/hsearch.h
+++ b/src/include/utils/hsearch.h
@@ -13,7 +13,7 @@
*/
#ifndef HSEARCH_H
#define HSEARCH_H
-
+#include "datatype/timestamp.h"
/*
* Hash functions must have this signature.
@@ -47,6 +47,7 @@ typedef void *(*HashAllocFunc) (Size request);
* HASHELEMENT is the private part of a hashtable entry. The caller's data
* follows the HASHELEMENT structure (on a MAXALIGN'd boundary). The hash key
* is expected to be at the start of the caller's hash entry data structure.
+ * If this hash is prunable, PRUNABLE_HASHELEMENT is used instead.
*/
typedef struct HASHELEMENT
{
@@ -54,12 +55,26 @@ typedef struct HASHELEMENT
uint32 hashvalue; /* hash function result for this entry */
} HASHELEMENT;
+typedef struct PRUNABLE_HASHELEMENT
+{
+ struct HASHELEMENT *link; /* link to next entry in same bucket */
+ uint32 hashvalue; /* hash function result for this entry */
+ TimestampTz last_access; /* timestamp of the last usage */
+ int naccess; /* takes 0 to 2, counted up when used */
+} PRUNABLE_HASHELEMENT;
+
/* Hash table header struct is an opaque type known only within dynahash.c */
typedef struct HASHHDR HASHHDR;
/* Hash table control struct is an opaque type known only within dynahash.c */
typedef struct HTAB HTAB;
+/*
+ * Hash pruning callback. This is called for the entries which is about to be
+ * removed without the owner's intention.
+ */
+typedef bool (*HASH_PRUNE_CB)(HTAB *hashp, void *ent);
+
/* Parameter data structure for hash_create */
/* Only those fields indicated by hash_flags need be set */
typedef struct HASHCTL
@@ -77,6 +92,9 @@ typedef struct HASHCTL
HashAllocFunc alloc; /* memory allocator */
MemoryContext hcxt; /* memory context to use for allocations */
HASHHDR *hctl; /* location of header in shared mem */
+ HASH_PRUNE_CB prune_cb; /* pruning callback. see above. */
+ int *memory_target; /* pointer to memory target */
+ int *prune_min_age; /* pointer to prune minimum age */
} HASHCTL;
/* Flags to indicate which parameters are supplied */
@@ -94,6 +112,7 @@ typedef struct HASHCTL
#define HASH_SHARED_MEM 0x0800 /* Hashtable is in shared memory */
#define HASH_ATTACH 0x1000 /* Do not initialize hctl */
#define HASH_FIXED_SIZE 0x2000 /* Initial size is a hard limit */
+#define HASH_PRUNABLE 0x4000 /* pruning setting */
/* max_dsize value to indicate expansible directory */
--
2.16.2
From 94c85baed46e1a8330af7d664c44289d97d6df26 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Mon, 12 Mar 2018 17:31:43 +0900
Subject: [PATCH 3/4] Apply purning to relcache
---
src/backend/utils/cache/relcache.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 9ee78f885f..da9ecee15b 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -3503,6 +3503,29 @@ RelationSetNewRelfilenode(Relation relation, char persistence,
#define INITRELCACHESIZE 400
+/* callback function for hash pruning */
+static bool
+relcache_prune_cb(HTAB *hashp, void *ent)
+{
+ RelIdCacheEnt *relent = (RelIdCacheEnt *) ent;
+ Relation relation;
+
+ /* this relation is requested to be removed. */
+ RelationIdCacheLookup(relent->reloid, relation);
+
+ /* but cannot remove cache entries currently in use */
+ if (!RelationHasReferenceCountZero(relation))
+ return false;
+
+ /*
+ * Otherwise we are allowd to forget it unconditionally. see
+ * RelationForgetRelation
+ */
+ RelationClearRelation(relation, false);
+
+ return true;
+}
+
void
RelationCacheInitialize(void)
{
@@ -3520,8 +3543,11 @@ RelationCacheInitialize(void)
MemSet(&ctl, 0, sizeof(ctl));
ctl.keysize = sizeof(Oid);
ctl.entrysize = sizeof(RelIdCacheEnt);
+
+ /* use the same setting with syscache */
+ ctl.prune_cb = relcache_prune_cb;
RelationIdCache = hash_create("Relcache by OID", INITRELCACHESIZE,
- &ctl, HASH_ELEM | HASH_BLOBS);
+ &ctl, HASH_ELEM | HASH_BLOBS | HASH_PRUNABLE);
/*
* relation mapper needs to be initialized too
--
2.16.2
From 89bb807c11ec411d1e25b0aa03792ae341435fec Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyotaro@lab.ntt.co.jp>
Date: Tue, 13 Mar 2018 17:29:32 +0900
Subject: [PATCH 4/4] PoC of generic plan removal of plancachesource.
---
src/backend/utils/cache/plancache.c | 157 ++++++++++++++++++++++++++++++++++++
src/backend/utils/hash/dynahash.c | 16 +++-
src/backend/utils/misc/guc.c | 21 +++++
src/backend/utils/mmgr/mcxt.c | 1 +
src/include/commands/prepare.h | 4 +
src/include/utils/hsearch.h | 2 +
src/include/utils/plancache.h | 14 +++-
7 files changed, 208 insertions(+), 7 deletions(-)
diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 8d7d8e04c9..9e34e4098e 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -63,12 +63,14 @@
#include "storage/lmgr.h"
#include "tcop/pquery.h"
#include "tcop/utility.h"
+#include "utils/catcache.h"
#include "utils/inval.h"
#include "utils/memutils.h"
#include "utils/resowner_private.h"
#include "utils/rls.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
+#include "utils/timestamp.h"
/*
@@ -86,6 +88,13 @@
* guarantee to save a CachedPlanSource without error.
*/
static CachedPlanSource *first_saved_plan = NULL;
+static CachedPlanSource *last_saved_plan = NULL;
+static int num_saved_plans = 0;
+static TimestampTz oldest_saved_plan = 0;
+
+/* GUC variables */
+int min_cached_plans = 1000;
+int plancache_prune_min_age = 600;
static void ReleaseGenericPlan(CachedPlanSource *plansource);
static List *RevalidateCachedQuery(CachedPlanSource *plansource,
@@ -105,6 +114,7 @@ static TupleDesc PlanCacheComputeResultDesc(List *stmt_list);
static void PlanCacheRelCallback(Datum arg, Oid relid);
static void PlanCacheFuncCallback(Datum arg, int cacheid, uint32 hashvalue);
static void PlanCacheSysCallback(Datum arg, int cacheid, uint32 hashvalue);
+static void PruneCachedPlan(void);
/*
@@ -207,6 +217,8 @@ CreateCachedPlan(RawStmt *raw_parse_tree,
plansource->generic_cost = -1;
plansource->total_custom_cost = 0;
plansource->num_custom_plans = 0;
+ plansource->last_access = GetCatCacheClock();
+
MemoryContextSwitchTo(oldcxt);
@@ -422,6 +434,28 @@ CompleteCachedPlan(CachedPlanSource *plansource,
plansource->is_valid = true;
}
+/* moves the plansource to the first in the list */
+static inline void
+MovePlansourceToFirst(CachedPlanSource *plansource)
+{
+ if (first_saved_plan != plansource)
+ {
+ /* delink this element */
+ if (plansource->next_saved)
+ plansource->next_saved->prev_saved = plansource->prev_saved;
+ if (plansource->prev_saved)
+ plansource->prev_saved->next_saved = plansource->next_saved;
+ if (last_saved_plan == plansource)
+ last_saved_plan = plansource->prev_saved;
+
+ /* insert at the beginning */
+ first_saved_plan->prev_saved = plansource;
+ plansource->next_saved = first_saved_plan;
+ plansource->prev_saved = NULL;
+ first_saved_plan = plansource;
+ }
+}
+
/*
* SaveCachedPlan: save a cached plan permanently
*
@@ -469,6 +503,11 @@ SaveCachedPlan(CachedPlanSource *plansource)
* Add the entry to the global list of cached plans.
*/
plansource->next_saved = first_saved_plan;
+ if (first_saved_plan)
+ first_saved_plan->prev_saved = plansource;
+ else
+ last_saved_plan = plansource;
+ plansource->prev_saved = NULL;
first_saved_plan = plansource;
plansource->is_saved = true;
@@ -491,7 +530,11 @@ DropCachedPlan(CachedPlanSource *plansource)
if (plansource->is_saved)
{
if (first_saved_plan == plansource)
+ {
first_saved_plan = plansource->next_saved;
+ if (first_saved_plan)
+ first_saved_plan->prev_saved = NULL;
+ }
else
{
CachedPlanSource *psrc;
@@ -501,10 +544,19 @@ DropCachedPlan(CachedPlanSource *plansource)
if (psrc->next_saved == plansource)
{
psrc->next_saved = plansource->next_saved;
+ if (psrc->next_saved)
+ psrc->next_saved->prev_saved = psrc;
break;
}
}
}
+
+ if (last_saved_plan == plansource)
+ {
+ last_saved_plan = plansource->prev_saved;
+ if (last_saved_plan)
+ last_saved_plan->next_saved = NULL;
+ }
plansource->is_saved = false;
}
@@ -536,6 +588,11 @@ ReleaseGenericPlan(CachedPlanSource *plansource)
Assert(plan->magic == CACHEDPLAN_MAGIC);
plansource->gplan = NULL;
ReleaseCachedPlan(plan, false);
+ if (plansource->is_saved)
+ {
+ Assert (num_saved_plans >= 1);
+ num_saved_plans--;
+ }
}
}
@@ -1146,6 +1203,15 @@ GetCachedPlan(CachedPlanSource *plansource, ParamListInfo boundParams,
if (useResOwner && !plansource->is_saved)
elog(ERROR, "cannot apply ResourceOwner to non-saved cached plan");
+ /* increment access counter and set timestamp */
+ if (plansource->is_saved)
+ {
+ plansource->last_access = GetCatCacheClock();
+
+ /* move this plan to the first of the list if needed */
+ MovePlansourceToFirst(plansource);
+ }
+
/* Make sure the querytree list is valid and we have parse-time locks */
qlist = RevalidateCachedQuery(plansource, queryEnv);
@@ -1154,6 +1220,11 @@ GetCachedPlan(CachedPlanSource *plansource, ParamListInfo boundParams,
if (!customplan)
{
+ /* Prune cached plans if needed */
+ if (plansource->is_saved &&
+ (min_cached_plans < 0 || num_saved_plans > min_cached_plans))
+ PruneCachedPlan();
+
if (CheckCachedPlan(plansource))
{
/* We want a generic plan, and we already have a valid one */
@@ -1166,6 +1237,12 @@ GetCachedPlan(CachedPlanSource *plansource, ParamListInfo boundParams,
plan = BuildCachedPlan(plansource, qlist, NULL, queryEnv);
/* Just make real sure plansource->gplan is clear */
ReleaseGenericPlan(plansource);
+
+
+ /* Prune cached plans if needed */
+ if (plansource->is_saved)
+ num_saved_plans++;
+
/* Link the new generic plan into the plansource */
plansource->gplan = plan;
plan->refcount++;
@@ -1853,6 +1930,86 @@ PlanCacheSysCallback(Datum arg, int cacheid, uint32 hashvalue)
ResetPlanCache();
}
+/*
+ * PrunePlanCache: invalidate "old" cached plans.
+ */
+static void
+PruneCachedPlan(void)
+{
+ CachedPlanSource *plansource;
+ TimestampTz currclock = GetCatCacheClock();
+ long age;
+ int us;
+ int nremoved = 0;
+
+ /* do nothing if not wanted */
+ if (plancache_prune_min_age < 0 || num_saved_plans <= min_cached_plans)
+ return;
+
+ /* Fast check for oldest cache */
+ if (oldest_saved_plan > 0)
+ {
+ TimestampDifference(oldest_saved_plan, currclock, &age, &us);
+ if (age < plancache_prune_min_age)
+ return;
+ }
+
+ /* last plan is the oldest. */
+ for (plansource = last_saved_plan; plansource; plansource = plansource->prev_saved)
+ {
+ long plan_age;
+ int us;
+
+ Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
+
+ /*
+ * No work if it already doesn't have gplan and move it to the
+ * beginning so that we don't see it at the next time
+ */
+ if (!plansource->gplan)
+ continue;
+
+ /*
+ * Check age for pruning. Can exit immediately when finding a
+ * not-older element.
+ */
+ TimestampDifference(plansource->last_access, currclock, &plan_age, &us);
+ if (plan_age <= plancache_prune_min_age)
+ {
+ /* this entry is the next oldest */
+ oldest_saved_plan = plansource->last_access;
+ break;
+ }
+
+ /*
+ * Here, remove generic plans of this plansrouceif it is not actually
+ * used and move it to the beginning of the list. Just update
+ * last_access and move it to the beginning if the plan is used.
+ */
+ if (plansource->gplan->refcount <= 1)
+ {
+ ReleaseGenericPlan(plansource);
+ nremoved++;
+ }
+
+ plansource->last_access = currclock;
+ }
+
+ /* move the "removed" plansrouces to the beginning of the list */
+ if (plansource != last_saved_plan && plansource)
+ {
+ plansource->next_saved->prev_saved = NULL;
+ first_saved_plan->prev_saved = last_saved_plan;
+ last_saved_plan->next_saved = first_saved_plan;
+ first_saved_plan = plansource->next_saved;
+ plansource->next_saved = NULL;
+ last_saved_plan = plansource;
+ }
+
+ if (nremoved > 0)
+ elog(DEBUG1, "plancache removed %d/%d", nremoved, num_saved_plans);
+}
+
/*
* ResetPlanCache: invalidate all cached plans.
*/
diff --git a/src/backend/utils/hash/dynahash.c b/src/backend/utils/hash/dynahash.c
index 5a8b15652a..a5b4979662 100644
--- a/src/backend/utils/hash/dynahash.c
+++ b/src/backend/utils/hash/dynahash.c
@@ -187,6 +187,8 @@ struct HASHHDR
int nelem_alloc; /* number of entries to allocate at once */
bool prunable; /* true if prunable */
HASH_PRUNE_CB prune_cb; /* pruning callback. see above. */
+ int *memory_target; /* pointer to memory target */
+ int *prune_min_age; /* pointer to prune minimum age */
#ifdef HASH_STATISTICS
@@ -510,6 +512,14 @@ hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
{
hctl->prunable = true;
hctl->prune_cb = info->prune_cb;
+ if (info->memory_target)
+ hctl->memory_target = info->memory_target;
+ else
+ hctl->memory_target = &syscache_memory_target;
+ if (info->prune_min_age)
+ hctl->prune_min_age = info->prune_min_age;
+ else
+ hctl->prune_min_age = &syscache_prune_min_age;
}
else
hctl->prunable = false;
@@ -1654,7 +1664,7 @@ prune_entries(HTAB *hashp)
has_seq_scans(hashp));
/* This setting prevents pruning */
- if (syscache_prune_min_age < 0)
+ if (*hctl->prune_min_age < 0)
return false;
/*
@@ -1663,7 +1673,7 @@ prune_entries(HTAB *hashp)
* settings is shared with syscache
*/
if (hctl->dsize * sizeof(HASHBUCKET) * hashp->ssize <
- (Size) syscache_memory_target * 1024L)
+ (Size) *hctl->memory_target * 1024L)
return false;
/*
@@ -1683,7 +1693,7 @@ prune_entries(HTAB *hashp)
TimestampDifference(helm->last_access, currclock, &entry_age, &us);
/* settings is shared with syscache */
- if (entry_age > syscache_prune_min_age)
+ if (entry_age > *hctl->prune_min_age)
{
/* Wait for the next chance if this is recently used */
if (helm->naccess > 0)
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 5e0d18657f..45aab61d62 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1995,6 +1995,27 @@ static struct config_int ConfigureNamesInt[] =
NULL, NULL, NULL
},
+ {
+ {"min_cached_plans", PGC_USERSET, RESOURCES_MEM,
+ gettext_noop("Sets the minimum number of cached plans kept on memory."),
+ gettext_noop("Timeout invalidation of plancache is not activated until the number of plancaches reaches
thisvalue. -1 means timeout invalidation is always active.")
+ },
+ &min_cached_plans,
+ 1000, -1, INT_MAX,
+ NULL, NULL, NULL
+ },
+
+ {
+ {"plancache_prune_min_age", PGC_USERSET, RESOURCES_MEM,
+ gettext_noop("Sets the minimum duration of plancache entries to remove."),
+ gettext_noop("Plancache items that live unused for loger than this seconds are considered to be
removed."),
+ GUC_UNIT_S
+ },
+ &plancache_prune_min_age,
+ 600, -1, INT_MAX,
+ NULL, NULL, NULL
+ },
+
/*
* We use the hopefully-safely-small value of 100kB as the compiled-in
* default for max_stack_depth. InitializeGUCOptions will increase it if
diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index d7baa54808..db225a06da 100644
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -194,6 +194,7 @@ MemoryContextResetChildren(MemoryContext context)
* but we have to recurse to handle the children.
* We must also delink the context from its parent, if it has one.
*/
+int hoge = 0;
void
MemoryContextDelete(MemoryContext context)
{
diff --git a/src/include/commands/prepare.h b/src/include/commands/prepare.h
index ffec029df4..1a8e8dd50e 100644
--- a/src/include/commands/prepare.h
+++ b/src/include/commands/prepare.h
@@ -31,6 +31,10 @@ typedef struct
CachedPlanSource *plansource; /* the actual cached plan */
bool from_sql; /* prepared via SQL, not FE/BE protocol? */
TimestampTz prepare_time; /* the time when the stmt was prepared */
+ RawStmt *raw_stmt;
+ int num_params;
+ Oid *param_types;
+ List *query_list;
} PreparedStatement;
diff --git a/src/include/utils/hsearch.h b/src/include/utils/hsearch.h
index df12352a46..7ea3c75423 100644
--- a/src/include/utils/hsearch.h
+++ b/src/include/utils/hsearch.h
@@ -93,6 +93,8 @@ typedef struct HASHCTL
MemoryContext hcxt; /* memory context to use for allocations */
HASHHDR *hctl; /* location of header in shared mem */
HASH_PRUNE_CB prune_cb; /* pruning callback. see above. */
+ int *memory_target; /* pointer to memory target */
+ int *prune_min_age; /* pointer to prune minimum age */
} HASHCTL;
/* Flags to indicate which parameters are supplied */
diff --git a/src/include/utils/plancache.h b/src/include/utils/plancache.h
index ab20aa04b0..b5d439985c 100644
--- a/src/include/utils/plancache.h
+++ b/src/include/utils/plancache.h
@@ -72,10 +72,11 @@ struct RawStmt;
* is no way to free memory short of clearing that entire context. A oneshot
* plan is always treated as unsaved.
*
- * Note: the string referenced by commandTag is not subsidiary storage;
- * it is assumed to be a compile-time-constant string. As with portals,
- * commandTag shall be NULL if and only if the original query string (before
- * rewriting) was an empty string.
+ * Note: the string referenced by commandTag is not subsidiary storage; it is
+ * assumed to be a compile-time-constant string. As with portals, commandTag
+ * shall be NULL if and only if the original query string (before rewriting)
+ * was an empty string. For memory-saving purpose, this struct is separated
+ * into to parts, the latter is removable in inactive state.
*/
typedef struct CachedPlanSource
{
@@ -110,11 +111,13 @@ typedef struct CachedPlanSource
bool is_valid; /* is the query_list currently valid? */
int generation; /* increments each time we create a plan */
/* If CachedPlanSource has been saved, it is a member of a global list */
+ struct CachedPlanSource *prev_saved; /* list link, if so */
struct CachedPlanSource *next_saved; /* list link, if so */
/* State kept to help decide whether to use custom or generic plans: */
double generic_cost; /* cost of generic plan, or -1 if not known */
double total_custom_cost; /* total cost of custom plans so far */
int num_custom_plans; /* number of plans included in total */
+ TimestampTz last_access; /* timestamp of the last usage */
} CachedPlanSource;
/*
@@ -143,6 +146,9 @@ typedef struct CachedPlan
MemoryContext context; /* context containing this CachedPlan */
} CachedPlan;
+/* GUC variables */
+extern int min_cached_plans;
+extern int plancache_prune_min_age;
extern void InitPlanCache(void);
extern void ResetPlanCache(void);
--
2.16.2
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