[Tarantool-patches] [PATCH v3 17/20] sql: introduce holder for prepared statemets
Sergey Ostanevich
sergos at tarantool.org
Mon Dec 23 23:54:29 MSK 2019
Hi!
Thank you for the patch! Below are two questions I have.
Thanks,
Sergos
On 20 Dec 15:47, Nikita Pettik wrote:
> This patch introduces holder (as data structure) to handle prepared
> statements and a set of interface functions (insert, delete, find) to
> operate on it. Holder under the hood is implemented as a global hash
> (keys are values of hash function applied to the original string containing
> SQL query; values are pointer to wrappers around compiled VDBE objects) and
> GC queue. Each entry in hash has reference counter. When it reaches 0
> value, entry is moved to GC queue. In case prepared statements holder is
> out of memory, it launches GC process: each entry in GC queue is deleted
> and all resources are released. Such approach allows to avoid workload
> spikes on session's disconnect (since on such event all statements must
> be deallocated).
> Each session is extended with local hash to map statement ids available
> for it. That is, session is allowed to execute and deallocate only
> statements which are previously prepared in scope of this session.
> On the other hand, global hash makes it possible to share same prepared
> statement object among different sessions.
> Size of cache is regulated via box.cfg{sql_cache_size} parameter.
>
> Part of #2592
> ---
> src/box/CMakeLists.txt | 1 +
> src/box/box.cc | 26 ++++
> src/box/box.h | 3 +
> src/box/errcode.h | 1 +
> src/box/lua/cfg.cc | 9 ++
> src/box/lua/load_cfg.lua | 3 +
> src/box/session.cc | 35 +++++
> src/box/session.h | 17 +++
> src/box/sql.c | 3 +
> src/box/sql_stmt_cache.c | 289 ++++++++++++++++++++++++++++++++++++++++
> src/box/sql_stmt_cache.h | 145 ++++++++++++++++++++
> test/app-tap/init_script.result | 37 ++---
> test/box/admin.result | 2 +
> test/box/cfg.result | 7 +
> test/box/cfg.test.lua | 1 +
> test/box/misc.result | 1 +
> 16 files changed, 562 insertions(+), 18 deletions(-)
> create mode 100644 src/box/sql_stmt_cache.c
> create mode 100644 src/box/sql_stmt_cache.h
>
> diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
> index 5cd5cba81..763bc3a4c 100644
> --- a/src/box/CMakeLists.txt
> +++ b/src/box/CMakeLists.txt
> @@ -126,6 +126,7 @@ add_library(box STATIC
> sql.c
> bind.c
> execute.c
> + sql_stmt_cache.c
> wal.c
> call.c
> merger.c
> diff --git a/src/box/box.cc b/src/box/box.cc
> index b119c927b..2b0cfa32d 100644
> --- a/src/box/box.cc
> +++ b/src/box/box.cc
> @@ -74,6 +74,7 @@
> #include "call.h"
> #include "func.h"
> #include "sequence.h"
> +#include "sql_stmt_cache.h"
>
> static char status[64] = "unknown";
>
> @@ -599,6 +600,17 @@ box_check_vinyl_options(void)
> }
> }
>
> +static int
> +box_check_sql_cache_size(int size)
> +{
> + if (size < 0) {
> + diag_set(ClientError, ER_CFG, "sql_cache_size",
> + "must be non-negative");
> + return -1;
> + }
> + return 0;
> +}
> +
> void
> box_check_config()
> {
> @@ -620,6 +632,7 @@ box_check_config()
> box_check_memtx_memory(cfg_geti64("memtx_memory"));
> box_check_memtx_min_tuple_size(cfg_geti64("memtx_min_tuple_size"));
> box_check_vinyl_options();
> + box_check_sql_cache_size(cfg_geti("sql_cache_size"));
> }
>
> /*
> @@ -886,6 +899,17 @@ box_set_net_msg_max(void)
> IPROTO_FIBER_POOL_SIZE_FACTOR);
> }
>
> +int
> +box_set_prepared_stmt_cache_size(void)
> +{
> + int cache_sz = cfg_geti("sql_cache_size");
> + if (box_check_sql_cache_size(cache_sz) != 0)
> + return -1;
> + if (sql_stmt_cache_set_size(cache_sz) != 0)
> + return -1;
> + return 0;
> +}
> +
> /* }}} configuration bindings */
>
> /**
> @@ -2096,6 +2120,8 @@ box_cfg_xc(void)
> box_check_instance_uuid(&instance_uuid);
> box_check_replicaset_uuid(&replicaset_uuid);
>
> + if (box_set_prepared_stmt_cache_size() != 0)
> + diag_raise();
> box_set_net_msg_max();
> box_set_readahead();
> box_set_too_long_threshold();
> diff --git a/src/box/box.h b/src/box/box.h
> index ccd527bd5..6806f1fc2 100644
> --- a/src/box/box.h
> +++ b/src/box/box.h
> @@ -236,6 +236,9 @@ void box_set_replication_sync_timeout(void);
> void box_set_replication_skip_conflict(void);
> void box_set_net_msg_max(void);
>
> +int
> +box_set_prepared_stmt_cache_size(void);
> +
> extern "C" {
> #endif /* defined(__cplusplus) */
>
> diff --git a/src/box/errcode.h b/src/box/errcode.h
> index c660b1c70..ee44f61b3 100644
> --- a/src/box/errcode.h
> +++ b/src/box/errcode.h
> @@ -258,6 +258,7 @@ struct errcode_record {
> /*203 */_(ER_BOOTSTRAP_READONLY, "Trying to bootstrap a local read-only instance as master") \
> /*204 */_(ER_SQL_FUNC_WRONG_RET_COUNT, "SQL expects exactly one argument returned from %s, got %d")\
> /*205 */_(ER_FUNC_INVALID_RETURN_TYPE, "Function '%s' returned value of invalid type: expected %s got %s") \
> + /*206 */_(ER_SQL_PREPARE, "Failed to prepare SQL statement: %s") \
>
> /*
> * !IMPORTANT! Please follow instructions at start of the file
> diff --git a/src/box/lua/cfg.cc b/src/box/lua/cfg.cc
> index 4884ce013..439af3cf9 100644
> --- a/src/box/lua/cfg.cc
> +++ b/src/box/lua/cfg.cc
> @@ -274,6 +274,14 @@ lbox_cfg_set_net_msg_max(struct lua_State *L)
> return 0;
> }
>
> +static int
> +lbox_set_prepared_stmt_cache_size(struct lua_State *L)
> +{
> + if (box_set_prepared_stmt_cache_size() != 0)
> + luaT_error(L);
> + return 0;
> +}
> +
> static int
> lbox_cfg_set_worker_pool_threads(struct lua_State *L)
> {
> @@ -378,6 +386,7 @@ box_lua_cfg_init(struct lua_State *L)
> {"cfg_set_replication_sync_timeout", lbox_cfg_set_replication_sync_timeout},
> {"cfg_set_replication_skip_conflict", lbox_cfg_set_replication_skip_conflict},
> {"cfg_set_net_msg_max", lbox_cfg_set_net_msg_max},
> + {"cfg_set_sql_cache_size", lbox_set_prepared_stmt_cache_size},
> {NULL, NULL}
> };
>
> diff --git a/src/box/lua/load_cfg.lua b/src/box/lua/load_cfg.lua
> index 85617c8f0..4463f989c 100644
> --- a/src/box/lua/load_cfg.lua
> +++ b/src/box/lua/load_cfg.lua
> @@ -81,6 +81,7 @@ local default_cfg = {
> feedback_host = "https://feedback.tarantool.io",
> feedback_interval = 3600,
> net_msg_max = 768,
> + sql_cache_size = 5 * 1024 * 1024,
> }
>
> -- types of available options
> @@ -144,6 +145,7 @@ local template_cfg = {
> feedback_host = 'string',
> feedback_interval = 'number',
> net_msg_max = 'number',
> + sql_cache_size = 'number',
> }
>
> local function normalize_uri(port)
> @@ -250,6 +252,7 @@ local dynamic_cfg = {
> instance_uuid = check_instance_uuid,
> replicaset_uuid = check_replicaset_uuid,
> net_msg_max = private.cfg_set_net_msg_max,
> + sql_cache_size = private.cfg_set_sql_cache_size,
> }
>
> --
> diff --git a/src/box/session.cc b/src/box/session.cc
> index 461d1cf25..881318252 100644
> --- a/src/box/session.cc
> +++ b/src/box/session.cc
> @@ -36,6 +36,7 @@
> #include "user.h"
> #include "error.h"
> #include "tt_static.h"
> +#include "sql_stmt_cache.h"
>
> const char *session_type_strs[] = {
> "background",
> @@ -141,6 +142,7 @@ session_create(enum session_type type)
> session_set_type(session, type);
> session->sql_flags = default_flags;
> session->sql_default_engine = SQL_STORAGE_ENGINE_MEMTX;
> + session->sql_stmts = NULL;
>
> /* For on_connect triggers. */
> credentials_create(&session->credentials, guest_user);
> @@ -178,6 +180,38 @@ session_create_on_demand()
> return s;
> }
>
> +bool
> +session_check_stmt_id(struct session *session, uint32_t stmt_id)
> +{
> + if (session->sql_stmts == NULL)
> + return false;
> + mh_int_t i = mh_i32ptr_find(session->sql_stmts, stmt_id, NULL);
> + return i != mh_end(session->sql_stmts);
> +}
> +
> +int
> +session_add_stmt_id(struct session *session, uint32_t id)
> +{
> + if (session->sql_stmts == NULL) {
> + session->sql_stmts = mh_i32ptr_new();
> + if (session->sql_stmts == NULL) {
> + diag_set(OutOfMemory, 0, "mh_i32ptr_new",
> + "session stmt hash");
> + return -1;
> + }
> + }
> + return sql_session_stmt_hash_add_id(session->sql_stmts, id);
> +}
> +
> +void
> +session_remove_stmt_id(struct session *session, uint32_t stmt_id)
> +{
> + assert(session->sql_stmts != NULL);
> + mh_int_t i = mh_i32ptr_find(session->sql_stmts, stmt_id, NULL);
> + assert(i != mh_end(session->sql_stmts));
> + mh_i32ptr_del(session->sql_stmts, i, NULL);
> +}
> +
> /**
> * To quickly switch to admin user when executing
> * on_connect/on_disconnect triggers in iproto.
> @@ -227,6 +261,7 @@ session_destroy(struct session *session)
> struct mh_i64ptr_node_t node = { session->id, NULL };
> mh_i64ptr_remove(session_registry, &node, NULL);
> credentials_destroy(&session->credentials);
> + sql_session_stmt_hash_erase(session->sql_stmts);
> mempool_free(&session_pool, session);
> }
>
> diff --git a/src/box/session.h b/src/box/session.h
> index eff3d7a67..6dfc7cba5 100644
> --- a/src/box/session.h
> +++ b/src/box/session.h
> @@ -101,6 +101,11 @@ struct session {
> const struct session_vtab *vtab;
> /** Session metadata. */
> union session_meta meta;
> + /**
> + * ID of statements prepared in current session.
> + * This map is allocated on demand.
> + */
> + struct mh_i32ptr_t *sql_stmts;
> /** Session user id and global grants */
> struct credentials credentials;
> /** Trigger for fiber on_stop to cleanup created on-demand session */
> @@ -267,6 +272,18 @@ session_storage_cleanup(int sid);
> struct session *
> session_create(enum session_type type);
>
> +/** Return true if given statement id belongs to the session. */
> +bool
> +session_check_stmt_id(struct session *session, uint32_t stmt_id);
> +
> +/** Add prepared statement ID to the session hash. */
> +int
> +session_add_stmt_id(struct session *session, uint32_t stmt_id);
> +
> +/** Remove prepared statement ID from the session hash. */
> +void
> +session_remove_stmt_id(struct session *session, uint32_t stmt_id);
> +
> /**
> * Destroy a session.
> * Must be called by the networking layer on disconnect.
> diff --git a/src/box/sql.c b/src/box/sql.c
> index f1df55571..455fabeef 100644
> --- a/src/box/sql.c
> +++ b/src/box/sql.c
> @@ -54,6 +54,7 @@
> #include "iproto_constants.h"
> #include "fk_constraint.h"
> #include "mpstream.h"
> +#include "sql_stmt_cache.h"
>
> static sql *db = NULL;
>
> @@ -74,6 +75,8 @@ sql_init()
> if (sql_init_db(&db) != 0)
> panic("failed to initialize SQL subsystem");
>
> + sql_stmt_cache_init();
> +
> assert(db != NULL);
> }
>
> diff --git a/src/box/sql_stmt_cache.c b/src/box/sql_stmt_cache.c
> new file mode 100644
> index 000000000..742e4135c
> --- /dev/null
> +++ b/src/box/sql_stmt_cache.c
> @@ -0,0 +1,289 @@
> +/*
> + * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
> + *
> + * Redistribution and use in source and binary forms, with or
> + * without modification, are permitted provided that the following
> + * conditions are met:
> + *
> + * 1. Redistributions of source code must retain the above
> + * copyright notice, this list of conditions and the
> + * following disclaimer.
> + *
> + * 2. Redistributions in binary form must reproduce the above
> + * copyright notice, this list of conditions and the following
> + * disclaimer in the documentation and/or other materials
> + * provided with the distribution.
> + *
> + * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
> + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
> + * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
> + * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
> + * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
> + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
> + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
> + * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
> + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
> + * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> + * SUCH DAMAGE.
> + */
> +#include "sql_stmt_cache.h"
> +
> +#include "assoc.h"
> +#include "error.h"
> +#include "execute.h"
> +#include "diag.h"
> +
> +static struct sql_stmt_cache sql_stmt_cache;
> +
> +void
> +sql_stmt_cache_init()
> +{
> + sql_stmt_cache.hash = mh_i32ptr_new();
> + if (sql_stmt_cache.hash == NULL)
> + panic("out of memory");
> + sql_stmt_cache.mem_quota = 0;
> + sql_stmt_cache.mem_used = 0;
> + rlist_create(&sql_stmt_cache.gc_queue);
> +}
> +
> +static size_t
> +sql_cache_entry_sizeof(struct sql_stmt *stmt)
> +{
> + return sql_stmt_est_size(stmt) + sizeof(struct stmt_cache_entry);
> +}
> +
> +static void
> +sql_cache_entry_delete(struct stmt_cache_entry *entry)
> +{
> + assert(entry->refs == 0);
> + assert(! sql_stmt_busy(entry->stmt));
> + sql_stmt_finalize(entry->stmt);
> + TRASH(entry);
> + free(entry);
> +}
> +
> +/**
> + * Remove statement entry from cache: firstly delete from hash,
> + * than remove from LRU list and account cache size changes,
> + * finally release occupied memory.
> + */
> +static void
> +sql_stmt_cache_delete(struct stmt_cache_entry *entry)
> +{
> + if (sql_stmt_cache.last_found == entry)
> + sql_stmt_cache.last_found = NULL;
> + rlist_del(&entry->link);
> + sql_stmt_cache.mem_used -= sql_cache_entry_sizeof(entry->stmt);
> + sql_cache_entry_delete(entry);
> +}
> +
> +static struct stmt_cache_entry *
> +stmt_cache_find_entry(uint32_t stmt_id)
> +{
> + if (sql_stmt_cache.last_found != NULL) {
> + const char *sql_str =
> + sql_stmt_query_str(sql_stmt_cache.last_found->stmt);
> + uint32_t last_stmt_id = sql_stmt_calculate_id(sql_str,
> + strlen(sql_str));
> + if (last_stmt_id == stmt_id)
> + return sql_stmt_cache.last_found;
> + /* Fallthrough to slow hash search. */
> + }
> + struct mh_i32ptr_t *hash = sql_stmt_cache.hash;
> + mh_int_t stmt = mh_i32ptr_find(hash, stmt_id, NULL);
> + if (stmt == mh_end(hash))
> + return NULL;
> + struct stmt_cache_entry *entry = mh_i32ptr_node(hash, stmt)->val;
> + if (entry == NULL)
> + return NULL;
> + sql_stmt_cache.last_found = entry;
> + return entry;
> +}
> +
> +static void
> +sql_stmt_cache_gc()
> +{
> + struct stmt_cache_entry *entry, *next;
> + rlist_foreach_entry_safe(entry, &sql_stmt_cache.gc_queue, link, next)
> + sql_stmt_cache_delete(entry);
> + assert(rlist_empty(&sql_stmt_cache.gc_queue));
> +}
> +
> +/**
> + * Allocate new cache entry containing given prepared statement.
> + * Add it to the LRU cache list. Account cache size enlargement.
> + */
> +static struct stmt_cache_entry *
> +sql_cache_entry_new(struct sql_stmt *stmt)
> +{
> + struct stmt_cache_entry *entry = malloc(sizeof(*entry));
> + if (entry == NULL) {
> + diag_set(OutOfMemory, sizeof(*entry), "malloc",
> + "struct stmt_cache_entry");
> + return NULL;
> + }
> + entry->stmt = stmt;
> + entry->refs = 0;
> + return entry;
> +}
> +
> +/**
> + * Return true if used memory (accounting new entry) for SQL
> + * prepared statement cache does not exceed the limit.
> + */
> +static bool
> +sql_cache_check_new_entry_size(size_t size)
> +{
> + return (sql_stmt_cache.mem_used + size <= sql_stmt_cache.mem_quota);
> +}
> +
> +static void
> +sql_stmt_cache_entry_unref(struct stmt_cache_entry *entry)
> +{
> + assert((int64_t)entry->refs - 1 >= 0);
> + if (--entry->refs == 0) {
> + /*
> + * Remove entry from hash and add it to gc queue.
> + * Resources are to be released in the nearest
> + * GC cycle (see sql_stmt_cache_insert()).
> + */
> + struct sql_stmt_cache *cache = &sql_stmt_cache;
> + const char *sql_str = sql_stmt_query_str(entry->stmt);
> + uint32_t stmt_id = sql_stmt_calculate_id(sql_str,
> + strlen(sql_str));
> + mh_int_t i = mh_i32ptr_find(cache->hash, stmt_id, NULL);
> + assert(i != mh_end(cache->hash));
> + mh_i32ptr_del(cache->hash, i, NULL);
> + rlist_add(&sql_stmt_cache.gc_queue, &entry->link);
> + if (sql_stmt_cache.last_found == entry)
> + sql_stmt_cache.last_found = NULL;
> + }
> +}
> +
> +void
> +sql_session_stmt_hash_erase(struct mh_i32ptr_t *hash)
> +{
> + if (hash == NULL)
> + return;
> + mh_int_t i;
> + struct stmt_cache_entry *entry;
> + mh_foreach(hash, i) {
> + entry = (struct stmt_cache_entry *)
> + mh_i32ptr_node(hash, i)->val;
> + sql_stmt_cache_entry_unref(entry);
> + }
> + mh_i32ptr_delete(hash);
> +}
> +
> +int
> +sql_session_stmt_hash_add_id(struct mh_i32ptr_t *hash, uint32_t stmt_id)
> +{
> + struct stmt_cache_entry *entry = stmt_cache_find_entry(stmt_id);
> + const struct mh_i32ptr_node_t id_node = { stmt_id, entry };
> + struct mh_i32ptr_node_t *old_node = NULL;
> + mh_int_t i = mh_i32ptr_put(hash, &id_node, &old_node, NULL);
> + if (i == mh_end(hash)) {
> + diag_set(OutOfMemory, 0, "mh_i32ptr_put", "mh_i32ptr_node");
> + return -1;
> + }
> + assert(old_node == NULL);
> + entry->refs++;
> + return 0;
> +}
> +
> +uint32_t
> +sql_stmt_calculate_id(const char *sql_str, size_t len)
> +{
> + return mh_strn_hash(sql_str, len);
> +}
> +
> +void
> +sql_stmt_unref(uint32_t stmt_id)
> +{
> + struct stmt_cache_entry *entry = stmt_cache_find_entry(stmt_id);
> + assert(entry != NULL);
> + sql_stmt_cache_entry_unref(entry);
> +}
> +
> +int
> +sql_stmt_cache_update(struct sql_stmt *old_stmt, struct sql_stmt *new_stmt)
> +{
> + const char *sql_str = sql_stmt_query_str(old_stmt);
> + uint32_t stmt_id = sql_stmt_calculate_id(sql_str, strlen(sql_str));
> + struct stmt_cache_entry *entry = stmt_cache_find_entry(stmt_id);
> + uint32_t ref_count = entry->refs;
Does this update can happen is such a way that statement can be
substituted by a different one, still with the same hash? In such a case
users of 'old_stmt' can see surprising results...
> + sql_stmt_cache_delete(entry);
> + if (sql_stmt_cache_insert(new_stmt) != 0) {
> + sql_stmt_finalize(new_stmt);
> + return -1;
> + }
> + /* Restore reference counter. */
> + entry = stmt_cache_find_entry(stmt_id);
> + entry->refs = ref_count;
> + return 0;
> +}
> +
> +int
> +sql_stmt_cache_insert(struct sql_stmt *stmt)
> +{
> + assert(stmt != NULL);
> + struct sql_stmt_cache *cache = &sql_stmt_cache;
> + size_t new_entry_size = sql_cache_entry_sizeof(stmt);
> +
> + if (! sql_cache_check_new_entry_size(new_entry_size))
> + sql_stmt_cache_gc();
> + /*
> + * Test memory limit again. Raise an error if it is
> + * still overcrowded.
> + */
> + if (! sql_cache_check_new_entry_size(new_entry_size)) {
> + diag_set(ClientError, ER_SQL_PREPARE, "Memory limit for SQL "\
> + "prepared statements has been reached. Please, deallocate "\
> + "active statements or increase SQL cache size.");
> + return -1;
> + }
> + struct mh_i32ptr_t *hash = cache->hash;
> + struct stmt_cache_entry *entry = sql_cache_entry_new(stmt);
> + if (entry == NULL)
> + return -1;
> + const char *sql_str = sql_stmt_query_str(stmt);
> + uint32_t stmt_id = sql_stmt_calculate_id(sql_str, strlen(sql_str));
> + assert(sql_stmt_cache_find(stmt_id) == NULL);
Good for debug, but what will we have in release, consider we will never
have a chance to test all possible statements?
> + const struct mh_i32ptr_node_t id_node = { stmt_id, entry };
> + struct mh_i32ptr_node_t *old_node = NULL;
> + mh_int_t i = mh_i32ptr_put(hash, &id_node, &old_node, NULL);
> + if (i == mh_end(hash)) {
> + sql_cache_entry_delete(entry);
> + diag_set(OutOfMemory, 0, "mh_i32ptr_put", "mh_i32ptr_node");
> + return -1;
> + }
> + assert(old_node == NULL);
> + sql_stmt_cache.mem_used += sql_cache_entry_sizeof(stmt);
> + return 0;
> +}
> +
> +struct sql_stmt *
> +sql_stmt_cache_find(uint32_t stmt_id)
> +{
> + struct stmt_cache_entry *entry = stmt_cache_find_entry(stmt_id);
> + if (entry == NULL)
> + return NULL;
> + return entry->stmt;
> +}
> +
> +int
> +sql_stmt_cache_set_size(size_t size)
> +{
> + if (sql_stmt_cache.mem_used > size)
> + sql_stmt_cache_gc();
> + if (sql_stmt_cache.mem_used > size) {
> + diag_set(ClientError, ER_SQL_PREPARE, "Can't reduce memory "\
> + "limit for SQL prepared statements: please, deallocate "\
> + "active statements");
> + return -1;
> + }
> + sql_stmt_cache.mem_quota = size;
> + return 0;
> +}
> diff --git a/src/box/sql_stmt_cache.h b/src/box/sql_stmt_cache.h
> new file mode 100644
> index 000000000..f3935a27f
> --- /dev/null
> +++ b/src/box/sql_stmt_cache.h
> @@ -0,0 +1,145 @@
> +#ifndef INCLUDES_PREP_STMT_H
> +#define INCLUDES_PREP_STMT_H
> +/*
> + * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
> + *
> + * Redistribution and use in source and binary forms, with or
> + * without modification, are permitted provided that the following
> + * conditions are met:
> + *
> + * 1. Redistributions of source code must retain the above
> + * copyright notice, this list of conditions and the
> + * following disclaimer.
> + *
> + * 2. Redistributions in binary form must reproduce the above
> + * copyright notice, this list of conditions and the following
> + * disclaimer in the documentation and/or other materials
> + * provided with the distribution.
> + *
> + * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
> + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
> + * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
> + * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
> + * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
> + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
> + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
> + * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
> + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
> + * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> + * SUCH DAMAGE.
> + */
> +#include <stdint.h>
> +#include <stdio.h>
> +
> +#include "small/rlist.h"
> +
> +#if defined(__cplusplus)
> +extern "C" {
> +#endif
> +
> +struct sql_stmt;
> +struct mh_i64ptr_t;
> +
> +struct stmt_cache_entry {
> + /** Prepared statement itself. */
> + struct sql_stmt *stmt;
> + /**
> + * Link to the next entry. All statements are to be
> + * evicted on the next gc cycle.
> + */
> + struct rlist link;
> + /**
> + * Reference counter. If it is == 0, entry gets
> + * into GC queue.
> + */
> + uint32_t refs;
> +};
> +
> +/**
> + * Global prepared statements holder.
> + */
> +struct sql_stmt_cache {
> + /** Size of memory currently occupied by prepared statements. */
> + size_t mem_used;
> + /** Max memory size that can be used for cache. */
> + size_t mem_quota;
> + /** Query id -> struct stmt_cahce_entry hash.*/
> + struct mh_i32ptr_t *hash;
> + /**
> + * After deallocation statements are not deleted, but
> + * moved to this list. GC process is triggered only
> + * when memory limit has reached. It allows to reduce
> + * workload on session's disconnect.
> + */
> + struct rlist gc_queue;
> + /**
> + * Last result of sql_stmt_cache_find() invocation.
> + * Since during processing prepared statement it
> + * may require to find the same statement several
> + * times.
> + */
> + struct stmt_cache_entry *last_found;
> +};
> +
> +/**
> + * Initialize global cache for prepared statements. Called once
> + * during database setup (in sql_init()).
> + */
> +void
> +sql_stmt_cache_init();
> +
> +/**
> + * Erase session local hash: unref statements belong to this
> + * session and deallocate hash itself.
> + * @hash is assumed to be member of struct session @sql_stmts.
> + */
> +void
> +sql_session_stmt_hash_erase(struct mh_i32ptr_t *hash);
> +
> +/**
> + * Add entry corresponding to prepared statement with given ID
> + * to session-local hash and increase its ref counter.
> + * @hash is assumed to be member of struct session @sql_stmts.
> + */
> +int
> +sql_session_stmt_hash_add_id(struct mh_i32ptr_t *hash, uint32_t stmt_id);
> +
> +/**
> + * Prepared statement ID is supposed to be hash value
> + * of the original SQL query string.
> + */
> +uint32_t
> +sql_stmt_calculate_id(const char *sql_str, size_t len);
> +
> +/** Unref prepared statement entry in global holder. */
> +void
> +sql_stmt_unref(uint32_t stmt_id);
> +
> +int
> +sql_stmt_cache_update(struct sql_stmt *old_stmt, struct sql_stmt *new_stmt);
> +
> +/**
> + * Save prepared statement to the prepared statement cache.
> + * Account cache size change. If the cache is full (i.e. memory
> + * quota is exceeded) diag error is raised. In case of success
> + * return id of prepared statement via output parameter @id.
> + */
> +int
> +sql_stmt_cache_insert(struct sql_stmt *stmt);
> +
> +/** Find entry by SQL string. In case of search fails it returns NULL. */
> +struct sql_stmt *
> +sql_stmt_cache_find(uint32_t stmt_id);
> +
> +
> +/** Set prepared cache size limit. */
> +int
> +sql_stmt_cache_set_size(size_t size);
> +
> +#if defined(__cplusplus)
> +} /* extern "C" { */
> +#endif
> +
> +#endif
> diff --git a/test/app-tap/init_script.result b/test/app-tap/init_script.result
> index 799297ba0..551a0bbeb 100644
> --- a/test/app-tap/init_script.result
> +++ b/test/app-tap/init_script.result
> @@ -31,24 +31,25 @@ box.cfg
> 26 replication_sync_timeout:300
> 27 replication_timeout:1
> 28 slab_alloc_factor:1.05
> -29 strip_core:true
> -30 too_long_threshold:0.5
> -31 vinyl_bloom_fpr:0.05
> -32 vinyl_cache:134217728
> -33 vinyl_dir:.
> -34 vinyl_max_tuple_size:1048576
> -35 vinyl_memory:134217728
> -36 vinyl_page_size:8192
> -37 vinyl_read_threads:1
> -38 vinyl_run_count_per_level:2
> -39 vinyl_run_size_ratio:3.5
> -40 vinyl_timeout:60
> -41 vinyl_write_threads:4
> -42 wal_dir:.
> -43 wal_dir_rescan_delay:2
> -44 wal_max_size:268435456
> -45 wal_mode:write
> -46 worker_pool_threads:4
> +29 sql_cache_size:5242880
> +30 strip_core:true
> +31 too_long_threshold:0.5
> +32 vinyl_bloom_fpr:0.05
> +33 vinyl_cache:134217728
> +34 vinyl_dir:.
> +35 vinyl_max_tuple_size:1048576
> +36 vinyl_memory:134217728
> +37 vinyl_page_size:8192
> +38 vinyl_read_threads:1
> +39 vinyl_run_count_per_level:2
> +40 vinyl_run_size_ratio:3.5
> +41 vinyl_timeout:60
> +42 vinyl_write_threads:4
> +43 wal_dir:.
> +44 wal_dir_rescan_delay:2
> +45 wal_max_size:268435456
> +46 wal_mode:write
> +47 worker_pool_threads:4
> --
> -- Test insert from detached fiber
> --
> diff --git a/test/box/admin.result b/test/box/admin.result
> index 6126f3a97..852c1cde8 100644
> --- a/test/box/admin.result
> +++ b/test/box/admin.result
> @@ -83,6 +83,8 @@ cfg_filter(box.cfg)
> - 1
> - - slab_alloc_factor
> - 1.05
> + - - sql_cache_size
> + - 5242880
> - - strip_core
> - true
> - - too_long_threshold
> diff --git a/test/box/cfg.result b/test/box/cfg.result
> index 5370bb870..331f5e986 100644
> --- a/test/box/cfg.result
> +++ b/test/box/cfg.result
> @@ -71,6 +71,8 @@ cfg_filter(box.cfg)
> | - 1
> | - - slab_alloc_factor
> | - 1.05
> + | - - sql_cache_size
> + | - 5242880
> | - - strip_core
> | - true
> | - - too_long_threshold
> @@ -170,6 +172,8 @@ cfg_filter(box.cfg)
> | - 1
> | - - slab_alloc_factor
> | - 1.05
> + | - - sql_cache_size
> + | - 5242880
> | - - strip_core
> | - true
> | - - too_long_threshold
> @@ -315,6 +319,9 @@ box.cfg{memtx_memory = box.cfg.memtx_memory}
> box.cfg{vinyl_memory = box.cfg.vinyl_memory}
> | ---
> | ...
> +box.cfg{sql_cache_size = box.cfg.sql_cache_size}
> + | ---
> + | ...
>
> --------------------------------------------------------------------------------
> -- Test of default cfg options
> diff --git a/test/box/cfg.test.lua b/test/box/cfg.test.lua
> index 56ccb6767..e6a90d770 100644
> --- a/test/box/cfg.test.lua
> +++ b/test/box/cfg.test.lua
> @@ -51,6 +51,7 @@ box.cfg{replicaset_uuid = '12345678-0123-5678-1234-abcdefabcdef'}
>
> box.cfg{memtx_memory = box.cfg.memtx_memory}
> box.cfg{vinyl_memory = box.cfg.vinyl_memory}
> +box.cfg{sql_cache_size = box.cfg.sql_cache_size}
>
> --------------------------------------------------------------------------------
> -- Test of default cfg options
> diff --git a/test/box/misc.result b/test/box/misc.result
> index d2a20307a..7e5d28b70 100644
> --- a/test/box/misc.result
> +++ b/test/box/misc.result
> @@ -554,6 +554,7 @@ t;
> 203: box.error.BOOTSTRAP_READONLY
> 204: box.error.SQL_FUNC_WRONG_RET_COUNT
> 205: box.error.FUNC_INVALID_RETURN_TYPE
> + 206: box.error.SQL_PREPARE
> ...
> test_run:cmd("setopt delimiter ''");
> ---
> --
> 2.15.1
>
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