[Tarantool-patches] [PATCH] sql: increase default cache size

[Leonid Vasiliev <lvasiliev@tarantool.org>]

Increase the maximum number of in-memory pages to use
for temporary tables.
(https://www.sqlite.org/compile.html#default_cache_size)

Part of #5609
---

Hi SQL team. It is a simplest part of #5609.
This patch increases the default SQL cache size by 10 times to 20 MB.
A similar experiment shows a 10% performance increase for some datasets.
(https://github.com/tarantool/tarantool/issues/5593#issuecomment-740044007).
Mons approved these changes. I haven't done any research to determine the
optimal value. So feel free to throw this patch away.

https://github.com/tarantool/tarantool/issues/5609
https://github.com/tarantool/tarantool/tree/lvasiliev/gh-5609-increase-default-sql-sort-cache-size

 src/box/CMakeLists.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
index 19203f7..7372179 100644
--- a/src/box/CMakeLists.txt
+++ b/src/box/CMakeLists.txt
@@ -218,6 +218,10 @@ if(CMAKE_BUILD_TYPE STREQUAL "Debug")
   add_definitions(-DSQL_DEBUG=1)
 endif()
 add_definitions(-DSQL_TEST=1)
+# Set the maximum number of in-memory pages to use for temporary tables.
+# 20000 * 1024 = 20480000 bytes.
+# (https://www.sqlite.org/compile.html#default_cache_size)
+add_definitions(-DSQL_DEFAULT_CACHE_SIZE=-20000)
 
 set(EXT_SRC_DIR ${CMAKE_SOURCE_DIR}/extra)
 set(EXT_BIN_DIR ${CMAKE_BINARY_DIR}/extra)
-- 
2.7.4