diff --git a/src/backend/access/common/detoast.c b/src/backend/access/common/detoast.c index 3547cdba56e..5049410e81f 100644 --- a/src/backend/access/common/detoast.c +++ b/src/backend/access/common/detoast.c @@ -20,6 +20,8 @@ #include "common/int.h" #include "common/pg_lzcompress.h" #include "utils/expandeddatum.h" +#include "utils/hsearch.h" +#include "utils/memutils.h" #include "utils/rel.h" static struct varlena *toast_fetch_datum(struct varlena *attr); @@ -29,6 +31,30 @@ static struct varlena *toast_fetch_datum_slice(struct varlena *attr, static struct varlena *toast_decompress_datum(struct varlena *attr); static struct varlena *toast_decompress_datum_slice(struct varlena *attr, int32 slicelength); +bool enable_toast_cache = false; + +HTAB *toastCache = NULL; +MemoryContext ToastCacheContext = NULL; + +static uint64 toast_cache_hits = 0; +static uint64 toast_cache_misses = 0; + +typedef struct toast_cache_key { + Oid toastrelid; + Oid valueid; +} toast_cache_key; + +typedef struct toast_cache_entry { + toast_cache_key key; + int32 size; + void *data; +} toast_cache_entry; + +static toast_cache_entry *toast_cache_lookup(Oid toastrelid, Oid valueid); +static void toast_cache_add_entry(Oid toastrelid, Oid valueid, struct varlena *attr); +static struct varlena *toast_cache_lookup_datum(toast_cache_key key); +static void toast_cache_store_datum(toast_cache_key key, struct varlena *attr); + /* ---------- * detoast_external_attr - * @@ -117,6 +143,28 @@ detoast_attr(struct varlena *attr) { if (VARATT_IS_EXTERNAL_ONDISK(attr)) { + struct varlena *result; + toast_cache_key key; + + /* calculate the cache key */ + { + struct varatt_external toast_pointer; + + /* Must copy to access aligned fields */ + VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); + + /* try lookup in the toast cache */ + key.toastrelid = toast_pointer.va_toastrelid; + key.valueid = toast_pointer.va_valueid; + } + + /* first try to lookup in the toast cache */ + result = toast_cache_lookup_datum(key); + + /* cache hit, we're done */ + if (result) + return result; + /* * This is an externally stored datum --- fetch it back from there */ @@ -129,6 +177,8 @@ detoast_attr(struct varlena *attr) attr = toast_decompress_datum(tmp); pfree(tmp); } + + toast_cache_store_datum(key, attr); } else if (VARATT_IS_EXTERNAL_INDIRECT(attr)) { @@ -644,3 +694,130 @@ toast_datum_size(Datum value) } return result; } + +static bool +toast_cache_init(void) +{ + HASHCTL ctl; + + if (!enable_toast_cache) + return false; + + /* already initialized */ + if (toastCache) + return true; + + toast_cache_hits = 0; + toast_cache_misses = 0; + + /* FIXME should really be per query */ + ToastCacheContext = AllocSetContextCreate(TopMemoryContext, + "TOAST cache context", + ALLOCSET_DEFAULT_SIZES); + + /* Make a new hash table for the cache */ + ctl.keysize = sizeof(toast_cache_key); + ctl.entrysize = sizeof(toast_cache_entry); + ctl.hcxt = ToastCacheContext; + + toastCache = hash_create("TOAST cache", + 128, &ctl, + HASH_ELEM | HASH_CONTEXT | HASH_BLOBS); + + return true; +} + +static toast_cache_entry * +toast_cache_lookup(Oid toastrelid, Oid valueid) +{ + toast_cache_key key; + toast_cache_entry *entry; + + /* make sure cache initialized */ + if (!toast_cache_init()) + return NULL; + + key.toastrelid = toastrelid; + key.valueid = valueid; + + entry = (toast_cache_entry *) hash_search(toastCache, &key, + HASH_FIND, NULL); + + if (entry) + toast_cache_hits++; + else + toast_cache_misses++; + + return entry; +} + +static void +toast_cache_add_entry(Oid toastrelid, Oid valueid, struct varlena *attr) +{ + bool found = false; + toast_cache_key key; + toast_cache_entry *entry; + + /* make sure cache initialized */ + if (!toast_cache_init()) + return; + + key.toastrelid = toastrelid; + key.valueid = valueid; + + entry = (toast_cache_entry *) hash_search(toastCache, &key, + HASH_ENTER, &found); + + Assert(!found); + + entry->size = VARSIZE_ANY_EXHDR(attr); + entry->data = MemoryContextAlloc(ToastCacheContext, entry->size); + memcpy(entry->data, VARDATA_ANY(attr), entry->size); +} + +static void +toast_cache_destroy(void) +{ + if (!toastCache) + return; + + elog(LOG, "AtEOXact_ToastCache hits %ld misses %ld ratio %.2f%%", + toast_cache_hits, toast_cache_misses, + (toast_cache_hits * 100.0) / Max(1, toast_cache_hits + toast_cache_misses)); + + MemoryContextDelete(ToastCacheContext); + + toastCache = NULL; + ToastCacheContext = NULL; +} + +void +AtEOXact_ToastCache(void) +{ + toast_cache_destroy(); +} + +static struct varlena * +toast_cache_lookup_datum(toast_cache_key key) +{ + toast_cache_entry *entry; + struct varlena *result = NULL; + + entry = toast_cache_lookup(key.toastrelid, key.valueid); + + if (!entry) + return NULL; + + result = (struct varlena *) palloc(entry->size + VARHDRSZ); + SET_VARSIZE(result, entry->size + VARHDRSZ); + + memcpy(VARDATA(result), entry->data, entry->size); + + return result; +} + +static void +toast_cache_store_datum(toast_cache_key key, struct varlena *attr) +{ + toast_cache_add_entry(key.toastrelid, key.valueid, attr); +} diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 70ab6e27a13..2cae3582026 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -21,6 +21,7 @@ #include #include "access/commit_ts.h" +#include "access/detoast.h" #include "access/multixact.h" #include "access/parallel.h" #include "access/subtrans.h" @@ -2381,6 +2382,7 @@ CommitTransaction(void) AtEOXact_Snapshot(true, false); AtEOXact_ApplyLauncher(true); AtEOXact_LogicalRepWorkers(true); + AtEOXact_ToastCache(); pgstat_report_xact_timestamp(0); ResourceOwnerDelete(TopTransactionResourceOwner); @@ -2671,6 +2673,7 @@ PrepareTransaction(void) /* we treat PREPARE as ROLLBACK so far as waking workers goes */ AtEOXact_ApplyLauncher(false); AtEOXact_LogicalRepWorkers(false); + AtEOXact_ToastCache(); pgstat_report_xact_timestamp(0); CurrentResourceOwner = NULL; @@ -2888,6 +2891,7 @@ AbortTransaction(void) AtEOXact_PgStat(false, is_parallel_worker); AtEOXact_ApplyLauncher(false); AtEOXact_LogicalRepWorkers(false); + AtEOXact_ToastCache(); pgstat_report_xact_timestamp(0); } diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c index 93ded31ed92..ceb3d3b953c 100644 --- a/src/backend/utils/misc/guc_tables.c +++ b/src/backend/utils/misc/guc_tables.c @@ -27,6 +27,7 @@ #endif #include "access/commit_ts.h" +#include "access/detoast.h" #include "access/gin.h" #include "access/slru.h" #include "access/toast_compression.h" @@ -1015,6 +1016,16 @@ struct config_bool ConfigureNamesBool[] = true, NULL, NULL, NULL }, + { + {"enable_toast_cache", PGC_USERSET, QUERY_TUNING_METHOD, + gettext_noop("Enables caching of detoasted values."), + NULL, + GUC_EXPLAIN + }, + &enable_toast_cache, + false, + NULL, NULL, NULL + }, { {"geqo", PGC_USERSET, QUERY_TUNING_GEQO, gettext_noop("Enables genetic query optimization."), diff --git a/src/include/access/detoast.h b/src/include/access/detoast.h index 12d8cdb356a..1a662c81388 100644 --- a/src/include/access/detoast.h +++ b/src/include/access/detoast.h @@ -79,4 +79,7 @@ extern Size toast_raw_datum_size(Datum value); */ extern Size toast_datum_size(Datum value); +extern PGDLLIMPORT bool enable_toast_cache; +extern void AtEOXact_ToastCache(void); + #endif /* DETOAST_H */