Hello
I would like to continue discussion regarding changing calling
convention for ShmemInitHash procedure:
http://www.postgresql.org/message-id/CA+TgmoZm=uowt8a_xasfoogwufeelj861ntadiceopyfehv...@mail.gmail.com
Currently this procedure has two arguments --- init_size and max_size.
But since shared hash tables have fixed size there is little sense to
pass two arguments. In fact currently ShmemInitHash is always called
with init_size == max_size with only one exception, InitLocks procedure
(see lock.c), which I believe is actually a bug.
Patch is attached.
What do you think?
--
Best regards,
Aleksander Alekseev
http://eax.me/
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 3d9b8e4..4213c3a 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -495,7 +495,7 @@ pgss_shmem_startup(void)
info.hash = pgss_hash_fn;
info.match = pgss_match_fn;
pgss_hash = ShmemInitHash("pg_stat_statements hash",
- pgss_max, pgss_max,
+ pgss_max,
&info,
HASH_ELEM | HASH_FUNCTION | HASH_COMPARE);
diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c
index 39e8baf..dd5acb7 100644
--- a/src/backend/storage/buffer/buf_table.c
+++ b/src/backend/storage/buffer/buf_table.c
@@ -62,7 +62,7 @@ InitBufTable(int size)
info.num_partitions = NUM_BUFFER_PARTITIONS;
SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table",
- size, size,
+ size,
&info,
HASH_ELEM | HASH_BLOBS | HASH_PARTITION);
}
diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index 81506ea..9df73b1 100644
--- a/src/backend/storage/ipc/shmem.c
+++ b/src/backend/storage/ipc/shmem.c
@@ -237,7 +237,7 @@ InitShmemIndex(void)
hash_flags = HASH_ELEM;
ShmemIndex = ShmemInitHash("ShmemIndex",
- SHMEM_INDEX_SIZE, SHMEM_INDEX_SIZE,
+ SHMEM_INDEX_SIZE,
&info, hash_flags);
}
@@ -250,14 +250,7 @@ InitShmemIndex(void)
* table at once. (In practice, all creations are done in the postmaster
* process; child processes should always be attaching to existing tables.)
*
- * max_size is the estimated maximum number of hashtable entries. This is
- * not a hard limit, but the access efficiency will degrade if it is
- * exceeded substantially (since it's used to compute directory size and
- * the hash table buckets will get overfull).
- *
- * init_size is the number of hashtable entries to preallocate. For a table
- * whose maximum size is certain, this should be equal to max_size; that
- * ensures that no run-time out-of-shared-memory failures can occur.
+ * max_size is the estimated maximum number of hashtable entries.
*
* Note: before Postgres 9.0, this function returned NULL for some failure
* cases. Now, it always throws error instead, so callers need not check
@@ -265,7 +258,6 @@ InitShmemIndex(void)
*/
HTAB *
ShmemInitHash(const char *name, /* table string name for shmem index */
- long init_size, /* initial table size */
long max_size, /* max size of the table */
HASHCTL *infoP, /* info about key and bucket size */
int hash_flags) /* info about infoP */
@@ -299,7 +291,7 @@ ShmemInitHash(const char *name, /* table string name for shmem index */
/* Pass location of hashtable header to hash_create */
infoP->hctl = (HASHHDR *) location;
- return hash_create(name, init_size, infoP, hash_flags);
+ return hash_create(name, max_size, infoP, hash_flags);
}
/*
diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c
index b30b7b1..df41b29 100644
--- a/src/backend/storage/lmgr/lock.c
+++ b/src/backend/storage/lmgr/lock.c
@@ -377,8 +377,7 @@ void
InitLocks(void)
{
HASHCTL info;
- long init_table_size,
- max_table_size;
+ long max_table_size;
bool found;
/*
@@ -386,7 +385,6 @@ InitLocks(void)
* calculations must agree with LockShmemSize!
*/
max_table_size = NLOCKENTS();
- init_table_size = max_table_size / 2;
/*
* Allocate hash table for LOCK structs. This stores per-locked-object
@@ -398,14 +396,12 @@ InitLocks(void)
info.num_partitions = NUM_LOCK_PARTITIONS;
LockMethodLockHash = ShmemInitHash("LOCK hash",
- init_table_size,
max_table_size,
&info,
HASH_ELEM | HASH_BLOBS | HASH_PARTITION);
/* Assume an average of 2 holders per lock */
max_table_size *= 2;
- init_table_size *= 2;
/*
* Allocate hash table for PROCLOCK structs. This stores
@@ -417,7 +413,6 @@ InitLocks(void)
info.num_partitions = NUM_LOCK_PARTITIONS;
LockMethodProcLockHash = ShmemInitHash("PROCLOCK hash",
- init_table_size,
max_table_size,
&info,
HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index 026d2b9..be73a60 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -1117,7 +1117,6 @@ InitPredicateLocks(void)
PredicateLockTargetHash = ShmemInitHash("PREDICATELOCKTARGET hash",
max_table_size,
- max_table_size,
&info,
HASH_ELEM | HASH_BLOBS |
HASH_PARTITION | HASH_FIXED_SIZE);
@@ -1145,7 +1144,6 @@ InitPredicateLocks(void)
PredicateLockHash = ShmemInitHash("PREDICATELOCK hash",
max_table_size,
- max_table_size,
&info,
HASH_ELEM | HASH_FUNCTION |
HASH_PARTITION | HASH_FIXED_SIZE);
@@ -1226,7 +1224,6 @@ InitPredicateLocks(void)
SerializableXidHash = ShmemInitHash("SERIALIZABLEXID hash",
max_table_size,
- max_table_size,
&info,
HASH_ELEM | HASH_BLOBS |
HASH_FIXED_SIZE);
diff --git a/src/include/storage/shmem.h b/src/include/storage/shmem.h
index 6468e66..50cf928 100644
--- a/src/include/storage/shmem.h
+++ b/src/include/storage/shmem.h
@@ -37,7 +37,7 @@ extern void InitShmemAllocation(void);
extern void *ShmemAlloc(Size size);
extern bool ShmemAddrIsValid(const void *addr);
extern void InitShmemIndex(void);
-extern HTAB *ShmemInitHash(const char *name, long init_size, long max_size,
+extern HTAB *ShmemInitHash(const char *name, long max_size,
HASHCTL *infoP, int hash_flags);
extern void *ShmemInitStruct(const char *name, Size size, bool *foundPtr);
extern Size add_size(Size s1, Size s2);
--
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