sqlite: Use SQLite's API for getting per-database page pools.
Chrome currently carries a SQLite patch at
0002-Use-seperate-page-cache-pools-for-each-sqlite-connec.patch
which forces per-database (technically, per-connection) page cache
pools. Asides from adding to our maintenance burden, the patch breaks an
assert() in SQLite's code, suggesting that it doesn't work as intended
anymore.
Fortunately, SQLite has a few supported ways of specifying whether
database connections use private page cache pools or a central pool. The
most convenient method for Chrome is the SQLITE_OPEN_PRIVATECACHE flag
on sqlite3_open_v2() [1].
This CL does the following:
1) Removes the SQLITE_SEPARATE_CACHE_POOLS build flag, which activates
Chrome's page cache pool patch. The patch (which becomes inert when
this CL lands) shall be removed from our SQLite version in a
follow-up CL, after this CL sticks.
2) Removes the SQLITE_ENABLE_MEMORY_MANAGEMENT build flag. This flag is
incompatible with private page cache pools, because it enables the
sqlite3_release_memory() function [2], which assumes a centralized
(shared) page cache pool [3]. Chrome doesn't use
sqlite3_release_memory() today, so the flag is unnecessary. If we
want to trim SQLite caches in response to memory pressure, we can
still use sqlite3_db_release_memory() [4] and track all the open
connections ourselves.
3) Adds the SQLITE_OPEN_PRIVATECACHE flag to our invocation of
sqlite3_open_v2().
[1] https://www.sqlite.org/c3ref/open.html
[2] https://www.sqlite.org/c3ref/release_memory.html
[3] https://www.sqlite.org/sharedcache.html
[4] https://www.sqlite.org/c3ref/db_release_memory.html
Bug: 906396
Change-Id: Ib3b08b26364ad86d173111fc4e554bd07bd91aa1
Reviewed-on: https://chromium-review.googlesource.com/c/1343789
Reviewed-by: Joshua Bell <[email protected]>
Commit-Queue: Victor Costan <[email protected]>
Cr-Commit-Position: refs/heads/master@{#609754}diff --git a/sql/database.cc b/sql/database.cc
index b1a7cdc5..a88e25a 100644
--- a/sql/database.cc
+++ b/sql/database.cc
@@ -1612,9 +1612,17 @@
// Custom memory-mapping VFS which reads pages using regular I/O on first hit.
sqlite3_vfs* vfs = VFSWrapper();
const char* vfs_name = (vfs ? vfs->zName : nullptr);
- int err =
- sqlite3_open_v2(file_name.c_str(), &db_,
- SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, vfs_name);
+
+ // The flags are documented at https://www.sqlite.org/c3ref/open.html.
+ //
+ // Chrome uses SQLITE_OPEN_PRIVATECACHE because SQLite is used by many
+ // disparate features with their own databases, and having separate page
+ // caches makes it easier to reason about each feature's performance in
+ // isolation.
+ int err = sqlite3_open_v2(
+ file_name.c_str(), &db_,
+ SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_PRIVATECACHE,
+ vfs_name);
if (err != SQLITE_OK) {
// Extended error codes cannot be enabled until a handle is
// available, fetch manually.
