[tarantool-patches] Re: [PATCH v1 4/4] sql: move Triggers to server

[Kirill Shcherbatov <kshcherbatov@tarantool.org>]

I'll send 2.0 patchset,

> 1. It is not swap still. Swap of A and B means that before swap
> A == value1, B = value2. After swap A == value2, B == value1.
> Here you have done this:
> A == B.
> 
> Do you understand why exactly swap is needed here? Please, answer.
> Do not skip the question.
Yes, it is clear for me now: this function provides an ability to rollback.

diff --git a/src/box/alter.cc b/src/box/alter.cc
index 23cd4a3..03c2d91 100644
--- a/src/box/alter.cc
+++ b/src/box/alter.cc
@@ -552,7 +552,9 @@ space_swap_triggers(struct space *new_space, struct space *old_space)
        rlist_swap(&new_space->on_replace, &old_space->on_replace);
        rlist_swap(&new_space->on_stmt_begin, &old_space->on_stmt_begin);
        /** Copy SQL Triggers pointer. */
+       struct Trigger *old_value = new_space->sql_triggers;
        new_space->sql_triggers = old_space->sql_triggers;
+       old_space->sql_triggers = old_value;
 }


> 
> 2. Space->sql_triggers leaks when I drop a space via Lua.

I've reworked a tuple format in separate commit, I'll send a new patch set that includes it a bit later.

diff --git a/src/box/lua/schema.lua b/src/box/lua/schema.lua
index dd5ce0a..4996565 100644
--- a/src/box/lua/schema.lua
+++ b/src/box/lua/schema.lua
@@ -463,6 +463,7 @@ box.schema.space.drop = function(space_id, space_name, opts)
     check_param_table(opts, { if_exists = 'boolean' })
     local _space = box.space[box.schema.SPACE_ID]
     local _index = box.space[box.schema.INDEX_ID]
+    local _trigger = box.space[box.schema.TRIGGER_ID]
     local _vindex = box.space[box.schema.VINDEX_ID]
     local _truncate = box.space[box.schema.TRUNCATE_ID]
     local _space_sequence = box.space[box.schema.SPACE_SEQUENCE_ID]
@@ -471,6 +472,11 @@ box.schema.space.drop = function(space_id, space_name, opts)
         -- Delete automatically generated sequence.
         box.schema.sequence.drop(sequence_tuple[2])
     end
+    local triggers = _trigger.index["space_id"]:select({space_id})
+    for i = #triggers, 1, -1 do
+        local v = triggers[i]
+        _trigger:delete{v[1]}
+    end
     local keys = _vindex:select(space_id)
     for i = #keys, 1, -1 do
         local v = keys[i]
diff --git a/src/box/space.c b/src/box/space.c
index b370b7c..d2aeecf 100644
--- a/src/box/space.c
+++ b/src/box/space.c
@@ -209,6 +209,11 @@ space_delete(struct space *space)
        trigger_destroy(&space->on_replace);
        trigger_destroy(&space->on_stmt_begin);
        space_def_delete(space->def);
+       /*
+        * SQL Triggers should be deleted with on_replace_dd_trigger
+        * initiated in LUA schema:delete.
+        */
+       assert(space->sql_triggers == NULL);
        space->vtab->destroy(space);
 }
 


> 
> 3. After you fix the leak, try this test to simulate WAL error and you
> will see a crash:
> 
> 	box.cfg{}
> 	box.sql.execute("CREATE TABLE t1(id INTEGER PRIMARY KEY, a INTEGER);");
> 	box.sql.execute("CREATE TABLE t2(id INTEGER PRIMARY KEY, a INTEGER);");
> 	box.sql.execute("CREATE TRIGGER t1t INSERT ON t1 BEGIN INSERT INTO t2 VALUES (1, 1); END;")
> 	box.error.injection.set("ERRINJ_WAL_IO", true)
> 	box.sql.execute("CREATE INDEX t1a ON t1(a);")
> 	box.error.injection.set("ERRINJ_WAL_IO", false)
> 	box.sql.execute("INSERT INTO t1 VALUES (3, 3);")
> 
There is no crash for now, I've included this test case:

+-- test crash on error.injection
+box.sql.execute("CREATE TABLE t1(id INTEGER PRIMARY KEY, a INTEGER);");
 ---
 ...
+box.sql.execute("CREATE TABLE t2(id INTEGER PRIMARY KEY, a INTEGER);");
 ---
 ...
+box.sql.execute("CREATE TRIGGER t1t INSERT ON t1 BEGIN INSERT INTO t2 VALUES (1, 1); END;")
+---
+...
+box.error.injection.set("ERRINJ_WAL_IO", true)
+---
+- ok
+...
+box.sql.execute("CREATE INDEX t1a ON t1(a);")
+---
+- error: Failed to write to disk
+...
+box.error.injection.set("ERRINJ_WAL_IO", false)
+---
+- ok
+...
+box.sql.execute("INSERT INTO t1 VALUES (3, 3);")
+---
+...
+box.sql.execute("SELECT * from t1");
+---
+- - [3, 3]
+...
+box.sql.execute("SELECT * from t2");
+---
+- - [1, 1]
+...
+box.sql.execute("DROP TABLE t1;")
+---
+...
+box.sql.execute("DROP TABLE t2;")

> 4. Fits in 3 lines.
+               int rc = sql_trigger_replace(sql_get(),
+                                            sql_trigger_name(old_trigger),
+                                            NULL, &new_trigger);

> 5. Extra new line.
@@ -3131,7 +3130,6 @@ triggers_task_rollback(struct trigger *trigger, void *event)
        }
 }
 
-

> 6. Why do you need stmt and stmt->old_tuple here? As I see,
> old_trigger != NULL is the same as stmt->old_tuple != NULL.

 static void
 triggers_task_commit(struct trigger *trigger, void *event)
 {
-       struct txn_stmt *stmt = txn_last_stmt((struct txn*) event);
        struct Trigger *old_trigger = (struct Trigger *)trigger->data;
-
-       if (stmt->old_tuple != NULL) {
-               /* DELETE, REPLACE trigger. */
-               sql_trigger_delete(sql_get(), old_trigger);
-       }
+       /* DELETE, REPLACE trigger. */
+       sql_trigger_delete(sql_get(), old_trigger);
 }


> 7. Please, do not create two branches for each case. You can make this
> function more compact.
> 8. Two extra lines.


> 9. Const char *.
-char *
+const char *
 sql_trigger_name(struct Trigger *trigger);

> 10. Why?
> 11. Same.
Dropped.

> 12. Still is not fixed from the previous review. 'Error' is unused.
> And why do you need snprintf here?
char *error = tt_static_buf();
snprintf(error, TT_STATIC_BUF_LEN, "%s", sql_error);
diag_set(ClientError, ER_SQL, error);
sqlite3DbFree(db, sql_error);

I believe this should be like this.
Done same in other places.