Add SQLite3.status to call sqlite3_status

CHANGELOG.md

@@ -15,6 +15,7 @@ This release drops support for Ruby 2.7. [#453] @flavorjones
 - Support the `SUPER_JOURNAL` flag which is an alias for `MASTER_JOURNAL` as of sqlite 3.33.0. [#467] @flavorjones
 - `Statement#stat` and `Statement#memused` introduced to report statistics. [#461] @fractaledmind
 - `Statement#sql` and `Statement#expanded_sql` introduced to retrieve the SQL statement associated with the `Statement` object. [#293, #498] @tenderlove
+- `SQLite3.status` introduced to return run-time status and reset high-water marks. See `SQLite3::Constants::Status` for details. [#520] @wjlroe
 
 
 ### Improved

ext/sqlite3/sqlite3.c

@@ -85,6 +85,42 @@ threadsafe_p(VALUE UNUSED(klass))
     return INT2NUM(sqlite3_threadsafe());
 }
 
+/*
+ * call-seq:
+ *   status(parameter) → Hash
+ *   status(parameter, reset_flag = false) → Hash
+ *
+ * Queries the SQLite3 library for run-time status information. Passing a truthy +reset_flag+ will
+ * reset the highwater mark to the current value.
+ *
+ * [Parameters]
+ * - +parameter+ (Integer, SQLite3::Constants::Status): The status parameter to query.
+ * - +reset_flag+ (Boolean): Whether to reset the highwater mark. (default is +false+)
+ *
+ * [Returns]
+ * A Hash containing +:current+ and +:highwater+ keys for integer values.
+ */
+static VALUE
+rb_sqlite3_status(int argc, VALUE *argv, VALUE klass)
+{
+    VALUE opArg, resetFlagArg;
+
+    rb_scan_args(argc, argv, "11", &opArg, &resetFlagArg);
+
+    int op = NUM2INT(opArg);
+    bool resetFlag = RTEST(resetFlagArg);
+
+    int pCurrent = 0;
+    int pHighwater = 0;
+    sqlite3_status(op, &pCurrent, &pHighwater, resetFlag);
+
+    VALUE hash = rb_hash_new();
+    rb_hash_aset(hash, ID2SYM(rb_intern("current")), INT2FIX(pCurrent));
+    rb_hash_aset(hash, ID2SYM(rb_intern("highwater")), INT2FIX(pHighwater));
+
+    return hash;
+}
+
 void
 init_sqlite3_constants(void)
 {
@@ -164,6 +200,7 @@ Init_sqlite3_native(void)
     rb_define_singleton_method(mSqlite3, "sqlcipher?", using_sqlcipher, 0);
     rb_define_singleton_method(mSqlite3, "libversion", libversion, 0);
     rb_define_singleton_method(mSqlite3, "threadsafe", threadsafe_p, 0);
+    rb_define_singleton_method(mSqlite3, "status", rb_sqlite3_status, -1);
     rb_define_const(mSqlite3, "SQLITE_VERSION", rb_str_new2(SQLITE_VERSION));
     rb_define_const(mSqlite3, "SQLITE_VERSION_NUMBER", INT2FIX(SQLITE_VERSION_NUMBER));
     rb_define_const(mSqlite3, "SQLITE_LOADED_VERSION", rb_str_new2(sqlite3_libversion()));

lib/sqlite3/constants.rb

@@ -116,5 +116,59 @@ module ErrorCode
       # sqlite_step() has finished executing
       DONE = 101
     end
+
+    #
+    # CAPI3REF: Status Parameters
+    #
+    # These integer constants designate various run-time status parameters
+    # that can be returned by SQLite3.status
+    #
+    module Status
+      # This parameter is the current amount of memory checked out using sqlite3_malloc(), either
+      # directly or indirectly. The figure includes calls made to sqlite3_malloc() by the
+      # application and internal memory usage by the SQLite library. Auxiliary page-cache memory
+      # controlled by SQLITE_CONFIG_PAGECACHE is not included in this parameter. The amount returned
+      # is the sum of the allocation sizes as reported by the xSize method in sqlite3_mem_methods.
+      MEMORY_USED = 0
+
+      # This parameter returns the number of pages used out of the pagecache memory allocator that
+      # was configured using SQLITE_CONFIG_PAGECACHE. The value returned is in pages, not in bytes.
+      PAGECACHE_USED = 1
+
+      # This parameter returns the number of bytes of page cache allocation which could not be
+      # satisfied by the SQLITE_CONFIG_PAGECACHE buffer and where forced to overflow to
+      # sqlite3_malloc(). The returned value includes allocations that overflowed because they where
+      # too large (they were larger than the "sz" parameter to SQLITE_CONFIG_PAGECACHE) and
+      # allocations that overflowed because no space was left in the page cache.
+      PAGECACHE_OVERFLOW = 2
+
+      # NOT USED
+      SCRATCH_USED = 3
+
+      # NOT USED
+      SCRATCH_OVERFLOW = 4
+
+      # This parameter records the largest memory allocation request handed to sqlite3_malloc() or
+      # sqlite3_realloc() (or their internal equivalents). Only the value returned in the
+      # *pHighwater parameter to sqlite3_status() is of interest. The value written into the
+      # *pCurrent parameter is undefined.
+      MALLOC_SIZE = 5
+
+      # The *pHighwater parameter records the deepest parser stack. The *pCurrent value is
+      # undefined. The *pHighwater value is only meaningful if SQLite is compiled with
+      # YYTRACKMAXSTACKDEPTH.
+      PARSER_STACK = 6
+
+      # This parameter records the largest memory allocation request handed to the pagecache memory
+      # allocator. Only the value returned in the *pHighwater parameter to sqlite3_status() is of
+      # interest. The value written into the *pCurrent parameter is undefined.
+      PAGECACHE_SIZE = 7
+
+      # NOT USED
+      SCRATCH_SIZE = 8
+
+      # This parameter records the number of separate memory allocations currently checked out.
+      MALLOC_COUNT = 9
+    end
   end
 end

test/test_sqlite3.rb

@@ -21,5 +21,21 @@ def test_threadsafe?
     def test_compiled_version_and_loaded_version
       assert_equal(SQLite3::SQLITE_VERSION, SQLite3::SQLITE_LOADED_VERSION)
     end
+
+    def test_status
+      status = SQLite3.status(SQLite3::Constants::Status::MEMORY_USED)
+      assert_operator(status.fetch(:current), :>=, 0)
+      assert_operator(status.fetch(:highwater), :>=, status.fetch(:current))
+    end
+
+    def test_status_reset_highwater_mark
+      status = SQLite3.status(SQLite3::Constants::Status::MEMORY_USED, false)
+      assert_operator(status.fetch(:current), :>=, 0)
+      assert_operator(status.fetch(:highwater), :>=, status.fetch(:current))
+
+      status = SQLite3.status(SQLite3::Constants::Status::MEMORY_USED, true)
+      assert_operator(status.fetch(:current), :>=, 0)
+      assert_operator(status.fetch(:highwater), :>=, status.fetch(:current))
+    end
   end
 end