[sql] SQLite patch to implement "smart" auto-vacuum.
SQLITE_FCNTL_CHUNK_SIZE can advise the VFS to resize files in quantum
amounts, to reduce fragmentation from tiny appends. This change allows
a new PRAGMA auto_vacuum_slack_pages to provide auto_vacuum with a hint
to only rearrange pages when an entire quantum can be released.
BUG=698010
Review-Url: https://codereview.chromium.org/2732553002
Cr-Commit-Position: refs/heads/master@{#459847}
diff --git a/sql/sqlite_features_unittest.cc b/sql/sqlite_features_unittest.cc
index 6ddcc61..0f124af 100644
--- a/sql/sqlite_features_unittest.cc
+++ b/sql/sqlite_features_unittest.cc
@@ -361,4 +361,96 @@
}
#endif
+#if !defined(USE_SYSTEM_SQLITE)
+// Test that Chromium's patch to make auto_vacuum integrate with
+// SQLITE_FCNTL_CHUNK_SIZE is working.
+TEST_F(SQLiteFeaturesTest, SmartAutoVacuum) {
+ // Turn on auto_vacuum, and set the page size low to make results obvious.
+ // These settings require re-writing the database, which VACUUM does.
+ ASSERT_TRUE(db().Execute("PRAGMA auto_vacuum = FULL"));
+ ASSERT_TRUE(db().Execute("PRAGMA page_size = 1024"));
+ ASSERT_TRUE(db().Execute("VACUUM"));
+
+ // Code-coverage of the PRAGMA set/get implementation.
+ const char kPragmaSql[] = "PRAGMA auto_vacuum_slack_pages";
+ ASSERT_EQ("0", sql::test::ExecuteWithResult(&db(), kPragmaSql));
+ ASSERT_TRUE(db().Execute("PRAGMA auto_vacuum_slack_pages = 4"));
+ ASSERT_EQ("4", sql::test::ExecuteWithResult(&db(), kPragmaSql));
+ // Max out at 255.
+ ASSERT_TRUE(db().Execute("PRAGMA auto_vacuum_slack_pages = 1000"));
+ ASSERT_EQ("255", sql::test::ExecuteWithResult(&db(), kPragmaSql));
+ ASSERT_TRUE(db().Execute("PRAGMA auto_vacuum_slack_pages = 0"));
+
+ // With page_size=1024, the following will insert rows which take up an
+ // overflow page, plus a small header in a b-tree node. An empty table takes
+ // a single page, so for small row counts each insert will add one page, and
+ // each delete will remove one page.
+ const char kCreateSql[] = "CREATE TABLE t (id INTEGER PRIMARY KEY, value)";
+ const char kInsertSql[] = "INSERT INTO t (value) VALUES (randomblob(980))";
+#if !defined(OS_WIN)
+ const char kDeleteSql[] = "DELETE FROM t WHERE id = (SELECT MIN(id) FROM t)";
+#endif
+
+ // This database will be 34 overflow pages plus the table's root page plus the
+ // SQLite header page plus the freelist page.
+ ASSERT_TRUE(db().Execute(kCreateSql));
+ {
+ sql::Statement s(db().GetUniqueStatement(kInsertSql));
+ for (int i = 0; i < 34; ++i) {
+ s.Reset(true);
+ ASSERT_TRUE(s.Run());
+ }
+ }
+ ASSERT_EQ("37", sql::test::ExecuteWithResult(&db(), "PRAGMA page_count"));
+
+ // http://sqlite.org/mmap.html indicates that Windows will silently fail when
+ // truncating a memory-mapped file. That pretty much invalidates these tests
+ // against the actual file size.
+#if !defined(OS_WIN)
+ // Each delete will delete a single page, including crossing a
+ // multiple-of-four boundary.
+ {
+ sql::Statement s(db().GetUniqueStatement(kDeleteSql));
+ for (int i = 0; i < 5; ++i) {
+ int64_t file_size_before, file_size_after;
+ ASSERT_TRUE(base::GetFileSize(db_path(), &file_size_before));
+
+ s.Reset(true);
+ ASSERT_TRUE(s.Run());
+
+ ASSERT_TRUE(base::GetFileSize(db_path(), &file_size_after));
+ ASSERT_EQ(file_size_after, file_size_before - 1024);
+ }
+ }
+
+ // Turn on "smart" auto-vacuum to remove 4 pages at a time.
+ ASSERT_TRUE(db().Execute("PRAGMA auto_vacuum_slack_pages = 4"));
+
+ // No pages removed, then four deleted at once.
+ {
+ sql::Statement s(db().GetUniqueStatement(kDeleteSql));
+ for (int i = 0; i < 3; ++i) {
+ int64_t file_size_before, file_size_after;
+ ASSERT_TRUE(base::GetFileSize(db_path(), &file_size_before));
+
+ s.Reset(true);
+ ASSERT_TRUE(s.Run());
+
+ ASSERT_TRUE(base::GetFileSize(db_path(), &file_size_after));
+ ASSERT_EQ(file_size_after, file_size_before);
+ }
+
+ int64_t file_size_before, file_size_after;
+ ASSERT_TRUE(base::GetFileSize(db_path(), &file_size_before));
+
+ s.Reset(true);
+ ASSERT_TRUE(s.Run());
+
+ ASSERT_TRUE(base::GetFileSize(db_path(), &file_size_after));
+ ASSERT_EQ(file_size_after, file_size_before - 4096);
+ }
+#endif
+}
+#endif // !defined(USE_SYSTEM_SQLITE)
+
} // namespace
