Julian Foad wrote on Fri, Feb 11, 2022 at 14:48:28 +0000: > On 'pristines-on-demand-on-mwf': ⋮ > I could do with some help on a SQL test FAIL, when testing against the > older WC format, in wc-queries-test 3: test_query_expectations(). It > looks like this: > > $ (SRC_DIR=$PWD; cd obj-dir/subversion/tests/libsvn_wc && > ./wc-queries-test --cleanup > --config-file=$SRC_DIR/subversion/tests/tests.conf > --srcdir=$SRC_DIR/subversion/tests/libsvn_wc --wc-format-version=1.14 3 > | sed "s#$SRC_DIR/##") > > subversion/tests/libsvn_wc/wc-queries-test.c:815: > (apr_err=SVN_ERR_TEST_FAILED) > svn_tests: E200006: STMT_SELECT_UNREFERENCED_PRISTINES: Uses pristine with > only 0 index component: ((null)) > SELECT checksum FROM pristine WHERE refcount = 0 > subversion/tests/libsvn_wc/wc-queries-test.c:868: > (apr_err=SVN_ERR_COMPOSED_ERROR) > svn_tests: E200042: Additional errors: > subversion/tests/libsvn_wc/wc-queries-test.c:868: > (apr_err=SVN_ERR_SQLITE_CONSTRAINT) > svn_tests: E200035: |SCAN TABLE pristine > FAIL: wc-queries-test 3: test query expectations > > The failure is within: > if (item->search > && ((item->expression_vars < 2 && is_node_table(item->table)) > || (item->expression_vars < 1)) > && !is_result_table(item->table)) > > I have taken a look and cannot work out what it means.
In short, it's checking whether SQLite is using sufficiently many index columns. STMT_SELECT_UNREFERENCED_PRISTINES does a table scan without using an index, meaning that query does O(N) work where N is the number of rows in the table. To confirm that, does the test pass if you do «CREATE INDEX foo ON pristine(refcount)» when creating the SQLite database the test runs on? I haven't looked to see whether that's the right fix. That would depend on whether STMT_SELECT_UNREFERENCED_PRISTINES needs to be performant, and if it does, on what kind of index would best serve it without affecting other queries (e.g., INSERTs and DELETEs to that table). > Maybe the statement needs to be made to match the exception clause > "in_list(primary_key_statements, i)", but that's just a semi-educated guess. The statements in that list both have «LIMIT 1» on them. That'd be why they're exempted from the "all queries must use an index" check. > Excuse brevity. Daniel
