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Some small fixes to the query cache.

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Docs/manual.texi:
  Some small changes to the MySQL-PostgreSQL comparison.
sql/item_timefunc.cc:
  Fixed typo.
sql/sql_cache.cc:
  More debugging
sql/sql_cache.h:
  More debugging
This commit is contained in:
unknown 2002-01-03 19:04:01 +02:00
parent b79170b7fd
commit 51a80eb212
4 changed files with 66 additions and 51 deletions
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66
Docs/manual.texi
View File

@ -4744,22 +4744,23 @@ MySQL Server offers the following advantages over PostgreSQL:
@itemize @bullet
@item
@code{MySQL} Server is generally much faster than PostgreSQL.
@code{MySQL} Server is generally much faster than PostgreSQL. MySQL
4.0.1 has also a query cache that can boost up the query speed for
mostly-read-only sites many times.
@item
MySQL has a much larger user base than PostgreSQL, therefore the
code is more tested and has historically proven more stable than
PostgreSQL. MySQL Server is the much more used in production
environments than PostgreSQL, mostly thanks to that MySQL AB,
formerly TCX DataKonsult AB, has provided top quality commercial support
for MySQL Server from the day it was released, whereas until recently
PostgreSQL was unsupported.
MySQL has a much larger user base than PostgreSQL, therefore the code is
more tested and has historically proven more stable than PostgreSQL.
MySQL Server is more used in production environments than PostgreSQL,
mostly thanks to that MySQL AB, formerly TCX DataKonsult AB, has
provided top quality commercial support for MySQL Server from the day it
was released, whereas until recently PostgreSQL was unsupported.
@item
MySQL Server works better on Windows than PostgreSQL does. MySQL Server runs as a
native Windows application (a service on NT/Win2000/WinXP), while
PostgreSQL is run under the @code{Cygwin} emulation. We have heard
that PostgreSQL is not yet that stable on Windows but we haven't
MySQL Server works better on Windows than PostgreSQL does. MySQL Server
runs as a native Windows application (a service on NT/Win2000/WinXP),
while PostgreSQL is run under the @code{Cygwin} emulation. We have
heard that PostgreSQL is not yet that stable on Windows but we haven't
been able to verify this ourselves.
@item
@ -4844,19 +4845,21 @@ You can access many databases from the same connection (depending of course
on your privileges).
@item
MySQL Server is coded from the start to be multi-threaded while PostgreSQL uses
processes. Context switching and access to common storage areas is much
faster between threads than between separate processes, this gives MySQL Server
a big speed advantage in multi-user applications and also makes it easier
for MySQL Server to take full advantage of symmetric multiprocessor (SMP) systems.
MySQL Server is coded from the start to be multi-threaded while
PostgreSQL uses processes. Context switching and access to common
storage areas is much faster between threads than between separate
processes, this gives MySQL Server a big speed advantage in multi-user
applications and also makes it easier for MySQL Server to take full
advantage of symmetric multiprocessor (SMP) systems.
@item
MySQL Server has a much more sophisticated privilege system than PostgreSQL.
While PostgreSQL only supports @code{INSERT}, @code{SELECT}, and
@code{UPDATE/DELETE} grants per user on a database or a table, MySQL Server allows
you to define a full set of different privileges on database, table and
column level. MySQL Server also allows you to specify the privilege on host and
user combinations. @xref{GRANT}.
MySQL Server has a much more sophisticated privilege system than
PostgreSQL. While PostgreSQL only supports @code{INSERT},
@code{SELECT}, and @code{UPDATE/DELETE} grants per user on a database or
a table, MySQL Server allows you to define a full set of different
privileges on database, table and column level. MySQL Server also
allows you to specify the privilege on host and user combinations.
@xref{GRANT}.
@item
MySQL Server supports a compressed client/server protocol which improves
@ -4880,16 +4883,17 @@ of a data file happens, usually from a hardware failure. It allows a
majority of the data to be recovered.
@item
Upgrading MySQL Server is painless. When you are upgrading MySQL Server, you don't need
to dump/restore your data, as you have to do with most PostgreSQL upgrades.
Upgrading MySQL Server is painless. When you are upgrading MySQL
Server, you don't need to dump/restore your data, as you have to do with
most PostgreSQL upgrades.
@end itemize
Drawbacks with MySQL Server compared to PostgreSQL:
@itemize @bullet
@item
The transaction support in MySQL Server is not yet as well tested as PostgreSQL's
system.
The transaction support in MySQL Server is not yet as well tested as
PostgreSQL's system.
@item
Because MySQL Server uses threads, which are not yet flawless on many OSes, one
@ -4914,10 +4918,10 @@ as in PostgreSQL. @xref{Adding functions}.
@item
Updates that run over multiple tables is harder to do in MySQL Server.
This will, however, be fixed in MySQL Server 4.0 with multi-table @code{UPDATE}
and in MySQL Server 4.1 with subselects.
In MySQL Server 4.0 one can use multi-table deletes to delete from many tables
at the same time. @xref{DELETE}.
This will, however, be fixed in MySQL Server 4.0.2 with multi-table
@code{UPDATE} and in MySQL Server 4.1 with subselects. In MySQL Server
4.0 one can use multi-table deletes to delete from many tables at the
same time. @xref{DELETE}.
@end itemize
PostgreSQL currently offers the following advantages over MySQL Server:

2
sql/item_timefunc.cc
View File

@ -1127,7 +1127,7 @@ longlong Item_extract::val_int()
void Item_typecast::print(String *str)
{
str->append("CASE(");
str->append("CAST(");
args[0]->print(str);
str->append(" AS ");
str->append(func_name());

45
sql/sql_cache.cc
View File

@ -344,7 +344,8 @@ inline Query_cache_block * Query_cache_block_table::block()
void Query_cache_block::init(ulong block_length)
{
DBUG_ENTER("Query_cache_block::init");
DBUG_PRINT("qcache", ("init block 0x%lx", (ulong) this));
DBUG_PRINT("qcache", ("init block 0x%lx length: %lu", (ulong) this,
block_length));
length = block_length;
used = 0;
type = Query_cache_block::FREE;
@ -587,7 +588,7 @@ void query_cache_insert(NET *net, const char *packet, ulong length)
}
else
STRUCT_UNLOCK(&query_cache.structure_guard_mutex);
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(););
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(0););
DBUG_VOID_RETURN;
}
@ -615,7 +616,7 @@ void query_cache_abort(NET *net)
}
net->query_cache_query=0;
STRUCT_UNLOCK(&query_cache.structure_guard_mutex);
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(););
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(0););
}
DBUG_VOID_RETURN;
}
@ -662,7 +663,7 @@ void query_cache_end_of_result(NET *net)
STRUCT_UNLOCK(&query_cache.structure_guard_mutex);
}
net->query_cache_query=0;
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(););
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(0););
}
DBUG_VOID_RETURN;
}
@ -670,7 +671,7 @@ void query_cache_end_of_result(NET *net)
void query_cache_invalidate_by_MyISAM_filename(const char *filename)
{
query_cache.invalidate_by_MyISAM_filename(filename);
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(););
DBUG_EXECUTE("check_querycache",query_cache.check_integrity(0););
}
@ -2482,6 +2483,7 @@ my_bool Query_cache::move_by_type(byte **border,
*pprev = block->pprev,
*pnext = block->pnext,
*new_block =(Query_cache_block *) *border;
uint tablename_offset = block->table()->table() - block->table()->db();
char *data = (char*) block->data();
byte *key;
uint key_length;
@ -2493,7 +2495,7 @@ my_bool Query_cache::move_by_type(byte **border,
new_block->type=Query_cache_block::TABLE;
new_block->used=used;
new_block->n_tables=1;
memcpy((char*) new_block->data(), data, len-new_block->headers_len());
memmove((char*) new_block->data(), data, len-new_block->headers_len());
relink(block, new_block, next, prev, pnext, pprev);
if (tables_blocks[new_block->table()->type()] == block)
tables_blocks[new_block->table()->type()] = new_block;
@ -2515,10 +2517,18 @@ my_bool Query_cache::move_by_type(byte **border,
nlist_root->prev = tnext;
tprev->next = nlist_root;
}
/*
Go through all queries that uses this table and change them to
point to the new table object
*/
Query_cache_table *new_block_table=new_block->table();
for (;tnext != nlist_root; tnext=tnext->next)
tnext->parent = new_block->table();
tnext->parent= new_block_table;
*border += len;
*before = new_block;
/* Fix pointer to table name */
new_block->table()->table(new_block->table()->db() + tablename_offset);
/* Fix hash to point at moved block */
hash_replace(&tables, tables.current_record, (byte*) new_block);
@ -2546,8 +2556,8 @@ my_bool Query_cache::move_by_type(byte **border,
uint key_length;
key=query_cache_query_get_key((byte*) block, &key_length, 0);
hash_search(&queries, (byte*) key, key_length);
memcpy((char*) new_block->table(0), (char*) block->table(0),
// Move table of used tables
memmove((char*) new_block->table(0), (char*) block->table(0),
ALIGN_SIZE(n_tables*sizeof(Query_cache_block_table)));
block->query()->unlock_n_destroy();
block->destroy();
@ -2555,7 +2565,7 @@ my_bool Query_cache::move_by_type(byte **border,
new_block->type=Query_cache_block::QUERY;
new_block->used=used;
new_block->n_tables=n_tables;
memcpy((char*) new_block->data(), data, len - new_block->headers_len());
memmove((char*) new_block->data(), data, len - new_block->headers_len());
relink(block, new_block, next, prev, pnext, pprev);
if (queries_blocks == block)
queries_blocks = new_block;
@ -2620,7 +2630,7 @@ my_bool Query_cache::move_by_type(byte **border,
new_block->init(len);
new_block->type=type;
new_block->used=used;
memcpy((char*) new_block->data(), data, len - new_block->headers_len());
memmove((char*) new_block->data(), data, len - new_block->headers_len());
relink(block, new_block, next, prev, pnext, pprev);
new_block->result()->parent(query_block);
Query_cache_query *query = query_block->query();
@ -2786,7 +2796,7 @@ void bins_dump() {}
void cache_dump() {}
void queries_dump() {}
void tables_dump() {}
my_bool check_integrity() { return 0; }
my_bool check_integrity(bool not_locked) { return 0; }
my_bool in_list(Query_cache_block * root, Query_cache_block * point,
const char *name) { return 0;}
my_bool in_blocks(Query_cache_block * point) { return 0; }
@ -2806,7 +2816,7 @@ void Query_cache::wreck(uint line, const char *message)
if (thd)
thd->killed = 1;
cache_dump();
/* check_integrity(); */ /* Can't call it here because of locks */
/* check_integrity(0); */ /* Can't call it here because of locks */
bins_dump();
DBUG_VOID_RETURN;
}
@ -2977,19 +2987,19 @@ void Query_cache::tables_dump()
}
my_bool Query_cache::check_integrity()
my_bool Query_cache::check_integrity(bool not_locked)
{
my_bool result = 0;
uint i;
STRUCT_LOCK(&structure_guard_mutex);
DBUG_ENTER("check_integrity");
if ( !initialized )
if (!initialized )
{
STRUCT_UNLOCK(&structure_guard_mutex);
DBUG_PRINT("qcache", ("Query Cache not initialized"));
DBUG_RETURN(0);
}
if (!not_locked)
STRUCT_LOCK(&structure_guard_mutex);
if (hash_check(&queries))
{
@ -3213,6 +3223,7 @@ my_bool Query_cache::check_integrity()
}
}
DBUG_ASSERT(result == 0);
if (!not_locked)
STRUCT_UNLOCK(&structure_guard_mutex);
DBUG_RETURN(result);
}

2
sql/sql_cache.h
View File

@ -391,7 +391,7 @@ protected:
void cache_dump();
void queries_dump();
void tables_dump();
my_bool check_integrity();
my_bool check_integrity(bool not_locked);
my_bool in_list(Query_cache_block * root, Query_cache_block * point,
const char *name);
my_bool in_blocks(Query_cache_block * point);