I have a case where I need to use conditional updates/inserts using peewee.
The query looks similar to what is shown here, conditional-duplicate-key-updates-with-mysql
As of now, what I'm doing is, do a get_or_create and then if it is not a create, check the condition in code and call and insert with on_conflict_replace.
But this is prone to race conditions, since the condition check happens back in web server, not in db server.
Is there a way to do the same with insert in peewee?
Using: AWS Aurora-MySQL-5.7
Yes, Peewee supports the ON DUPLICATE KEY UPDATE syntax. Here's an example from the docs:
class User(Model):
username = TextField(unique=True)
last_login = DateTimeField(null=True)
login_count = IntegerField()
# Insert a new user.
User.create(username='huey', login_count=0)
# Simulate the user logging in. The login count and timestamp will be
# either created or updated correctly.
now = datetime.now()
rowid = (User
.insert(username='huey', last_login=now, login_count=1)
.on_conflict(
preserve=[User.last_login], # Use the value we would have inserted.
update={User.login_count: User.login_count + 1})
.execute())
Doc link: http://docs.peewee-orm.com/en/latest/peewee/querying.html#upsert
The SQLite JSON1 extension has some really neat capabilities. However, I have not been able to figure out how I can update or insert individual JSON attribute values.
Here is an example
CREATE TABLE keywords
(
id INTEGER PRIMARY KEY,
lang INTEGER NOT NULL,
kwd TEXT NOT NULL,
locs TEXT NOT NULL DEFAULT '{}'
);
CREATE INDEX kwd ON keywords(lang,kwd);
I am using this table to store keyword searches and recording the locations from which the search was ininitated in the object locs. A sample entry in this database table would be like the one shown below
id:1,lang:1,kwd:'stackoverflow',locs:'{"1":1,"2":1,"5":1}'
The location object attributes here are indices to the actual locations stored elsewhere.
Now imagine the following scenarios
A search for stackoverflow is initiated from location index "2". In this case I simply want to increment the value at that index so that after the operation the corresponding row reads
id:1,lang:1,kwd:'stackoverflow',locs:'{"1":1,"2":2,"5":1}'
A search for stackoverflow is initiated from a previously unknown location index "7" in which case the corresponding row after the update would have to read
id:1,lang:1,kwd:'stackoverflow',locs:'{"1":1,"2":1,"5":1,"7":1}'
It is not clear to me that this can in fact be done. I tried something along the lines of
UPDATE keywords json_set(locs,'$.2','2') WHERE kwd = 'stackoverflow';
which gave the error message error near json_set. I'd be most obliged to anyone who might be able to tell me how/whether this should/can be done.
It is not necessary to create such complicated SQL with subqueries to do this.
The SQL below would solve your needs.
UPDATE keywords
SET locs = json_set(locs,'$.7', IFNULL(json_extract(locs, '$.7'), 0) + 1)
WHERE kwd = 'stackoverflow';
I know this is old, but it's like the first link when searching, it deserves a better solution.
I could have just deleted this question but given that the SQLite JSON1 extension appears to be relatively poorly understood I felt it would be more useful to provide an answer here for the benefit of others. What I have set out to do here is possible but the SQL syntax is rather more convoluted.
UPDATE keywords set locs =
(select json_set(json(keywords.locs),'$.**N**',
ifnull(
(select json_extract(keywords.locs,'$.**N**') from keywords where id = '1'),
0)
+ 1)
from keywords where id = '1')
where id = '1';
will accomplish both of the updates I have described in my original question above. Given how complicated this looks a few explanations are in order
The UPDATE keywords part does the actual updating, but it needs to know what to updatte
The SELECT json_set part is where we establish the value to be updated
If the relevant value does not exsit in the first place we do not want to do a + 1 on a null value so we do an IFNULL TEST
The WHERE id = bits ensure that we target the right row
Having now worked with JSON1 in SQLite for a while I have a tip to share with others going down the same road. It is easy to waste your time writing extremely convoluted and hard to maintain SQL in an effort to perform in-place JSON manipulation. Consider using SQLite in memory tables - CREATE TEMP TABLE... to store intermediate results and write a sequence of SQL statements instead. This makes the code a whole lot eaiser to understand and to maintain.
I have a problem inserting a related row through Entity Framework 5. I'm using it with RIA Services and .NET Framework version 4.5. The database system is MySQL 5.6. The connector version is 6.6.5.
It raises a Foreign Key constraint exception.
I've chosen to simplify the model to expose my issue.
LDM
Provider(id, name, address)
Article(id, name, price)
LinkToProvider(provider_id, article_id, provider_price)
// Id's are auto_increment columns.
First I create a new instance of Article. I add an instance of LinkToProvider to the LinkProvider collection of the article. In this LinkToProvider object the product itself is referenced. An existing provider is also referenced.
Then I submit the changes.
Sample code from the DataViewModel
this.CurrentArticle = new Article();
...
this.CurrentArticle.LinkToProvider.Add(
new LinkToProvider { Article = this.CurrentArticle, Provider =
this.ProviderCollection.CurrentItem }
);
...
this.DomainContext.articles.Add(this.CurrentArticle);
this.DomainContext.SubmitChanges();
NOTE :
At the begining Entity Framework inserts the product well. Then it fails because it tries to insert a row in the LinkToPrivder table with an unkown product id like the following.
INSERT
INTO LinkToProvider
VALUES(5, 0, 1.2)
It puts 0 instead of the generated id.
But if I insert a product alone without any relations the product id is generated in the database correctly.
Any help will be much appreciated !
Thank you.
I found the answer.
You need to bind the result from the stored procedure to the id column in the edmx model
So I have to modify my stored procedure to add an instruction to show the last instered id for the article table on the standard output.
SELECT LAST_INSERT_ID() AS NewArticleId;
Then I added the binding with the name of the column name returned by the stored procedure. Here it's NewArticleId.
It's explained here : http://learnentityframework.com/LearnEntityFramework/tutorials/using-stored-procedures-for-insert-update-amp-delete-in-an-entity-data-model/.
I'm trying to update the column visited to give it the value 1. I use MySQL workbench, and I'm writing the statement in the SQL editor from inside the workbench. I'm writing the following command:
UPDATE tablename SET columnname=1;
It gives me the following error:
You are using safe update mode and you tried to update a table without
a WHERE that uses a KEY column To disable safe mode, toggle the option
....
I followed the instructions, and I unchecked the safe update option from the Edit menu then Preferences then SQL Editor. The same error still appear & I'm not able to update this value. Please, tell me what is wrong?
It looks like your MySql session has the safe-updates option set. This means that you can't update or delete records without specifying a key (ex. primary key) in the where clause.
Try:
SET SQL_SAFE_UPDATES = 0;
Or you can modify your query to follow the rule (use primary key in where clause).
Follow the following steps before executing the UPDATE command:
In MySQL Workbench
Go to Edit --> Preferences
Click "SQL Editor" tab and uncheck "Safe Updates" check box
Query --> Reconnect to Server // logout and then login
Now execute your SQL query
p.s., No need to restart the MySQL daemon!
SET SQL_SAFE_UPDATES = 0;
# your code SQL here
SET SQL_SAFE_UPDATES = 1;
SET SQL_SAFE_UPDATES=0;
UPDATE tablename SET columnname=1;
SET SQL_SAFE_UPDATES=1;
No need to set SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way. SAFE_UPDATES is by default on for a REASON. You can drive a car without safety belts and other things if you know what I mean ;)
Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:
UPDATE customers SET countryCode = 'USA'
WHERE country = 'USA'; -- which gives the error, you just write:
UPDATE customers SET countryCode = 'USA'
WHERE (country = 'USA' AND customerNumber <> 0); -- Because customerNumber is a primary key you got no error 1175 any more.
Now you can be assured every record is (ALWAYS) updated as you expect.
Error Code: 1175. You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column To disable safe mode, toggle the option in Preferences -> SQL Editor and reconnect.
Turn OFF "Safe Update Mode" temporary
SET SQL_SAFE_UPDATES = 0;
UPDATE options SET title= 'kiemvieclam24h' WHERE url = 'http://kiemvieclam24h.net';
SET SQL_SAFE_UPDATES = 1;
Turn OFF "Safe Update Mode" forever
Mysql workbench 8.0:
MySQL Workbench => [ Edit ] => [ Preferences ] -> [ SQL Editor ] -> Uncheck "Safe Updates"
Old version can:
MySQL Workbench => [Edit] => [Preferences] => [SQL Queries]
Preferences...
"Safe Updates"...
Restart server
SET SQL_SAFE_UPDATES=0;
OR
Go to Edit --> Preferences
Click SQL Queries tab and uncheck Safe Updates check box
Query --> Reconnect to Server
Now execute your sql query
If you are in a safe mode, you need to provide id in where clause. So something like this should work!
UPDATE tablename SET columnname=1 where id>0
On WorkBench I resolved it By deactivating the safe update mode:
-Edit -> Preferences -> Sql Editor then uncheck Safe update.
The simplest solution is to define the row limit and execute. This is done for safety purposes.
I found the answer. The problem was that I have to precede the table name with the schema name. i.e, the command should be:
UPDATE schemaname.tablename SET columnname=1;
Thanks all.
In the MySQL Workbech version 6.2 don't exits the PreferenceSQLQueriesoptions.
In this case it's possible use: SET SQL_SAFE_UPDATES=0;
Since the question was answered and had nothing to do with safe updates, this might be the wrong place; I'll post just to add information.
I tried to be a good citizen and modified the query to use a temp table of ids that would get updated:
create temporary table ids ( id int )
select id from prime_table where condition = true;
update prime_table set field1 = '' where id in (select id from ids);
Failure. Modified the update to:
update prime_table set field1 = '' where id <> 0 and id in (select id from ids);
That worked. Well golly -- if I am always adding where key <> 0 to get around the safe update check, or even set SQL_SAFE_UPDATE=0, then I've lost the 'check' on my query. I might as well just turn off the option permanently. I suppose it makes deleting and updating a two step process instead of one.. but if you type fast enough and stop thinking about the key being special but rather as just a nuisance..
I too got the same issue but when I off 'safe updates' in Edit ->
Preferences -> SQL Editor -> Safe Updates, still I use to face the
error as "Error code 1175 disable safe mode"
My solution for this error is just given the primary key to the table if not given and update the column using those primary key value.
Eg: UPDATE [table name] SET Empty_Column = 'Value' WHERE
[primary key column name] = value;
True, this is pointless for the most examples. But finally, I came to the following statement and it works fine:
update tablename set column1 = '' where tablename .id = (select id from tablename2 where tablename2.column2 = 'xyz');
This is for Mac, but must be same for other OS except the location of the preferences.
The error we get when we try an unsafe DELETE operation
On the new window, uncheck the option Safe updates
Then close and reopen the connection. No need to restart the service.
Now we are going to try the DELETE again with successful results.
So what is all about this safe updates? It is not an evil thing. This is what MySql says about it.
Using the --safe-updates Option
For beginners, a useful startup option is --safe-updates (or
--i-am-a-dummy, which has the same effect). It is helpful for cases when you might have issued a DELETE FROM tbl_name statement but
forgotten the WHERE clause. Normally, such a statement deletes all
rows from the table. With --safe-updates, you can delete rows only by
specifying the key values that identify them. This helps prevent
accidents.
When you use the --safe-updates option, mysql issues the following
statement when it connects to the MySQL server:
SET sql_safe_updates=1, sql_select_limit=1000, sql_max_join_size=1000000;
It is safe to turn on this option while you deal with production database. Otherwise, you must be very careful not accidentally deleting important data.
just type SET SQL_SAFE_UPDATES = 0; before the delete or update and set to 1 again
SET SQL_SAFE_UPDATES = 1
If you're having this problem in a stored procedure and you aren't able to use the key in the WHERE clause, you can solve this by declaring a variable that will hold the limit of the rows that should be updated and then use it in the update/delete query.
DELIMITER $
CREATE PROCEDURE myProcedure()
BEGIN
DECLARE the_limit INT;
SELECT COUNT(*) INTO the_limit
FROM my_table
WHERE my_column IS NULL;
UPDATE my_table
SET my_column = true
WHERE my_column IS NULL
LIMIT the_limit;
END$
As stated in previous posts, changing the default settings of the database server will result in undesired modification of existing data due to an incorrect query on the data in a published project. Therefore, to implement such commands as stated in previous posts, it is necessary to run them in a test environment on sample data and then execute them after testing them correctly.
My suggestion is to write a WHERE conditional statement that will loop through all the rows in all conditions if an update should work for all rows in a table. For example, if the table contains an ID value, the condition ID > 0 can be used to select all rows:
/**
* For successful result, "id" column must be "Not Null (NN)" and defined in
* INT data type. In addition, the "id" column in the table must have PK, UQ
* and AI attributes.
*/
UPDATE schema_name.table_name
SET first_column_name = first_value, second_column_name = second_value, ...
WHERE id > 0;
If the table does not contain an id column, the update operation can be run on all rows by checking a column that cannot be null:
/**
* "first_column_name" column must be "Not Null (NN)" for successful result.
*/
UPDATE schema_name.table_name
SET first_column_name = first_value, second_column_name = second_value, ...
WHERE table_name.first_column_name IS NOT NULL;
MySql workbench gave me the same error, after I unchecked safe mode , I then reconnected the server and the update function worked.
Go to Query in the menu bar and reconnect the server
Query Menu -> Reconnect to Server
You can enable and disable safe update option by following commands.
To Disable,
SET SQL_SAFE_UPDATES=0;
or
SET SQL_SAFE_UPDATES=OFF;
To Enable,
SET SQL_SAFE_UPDATES=1;
or
SET SQL_SAFE_UPDATES=ON;
First:
Please make sure you want to update all records in that table because without the where clause it is dangerous to update all records in that table. It's rare time you want to update all records in the table.
most of the time you want to update specific records which should include where cluase if again you want to update all records open MySQL workbench> Edit> Preference>SQL Editor > scroll down at right and uncheck the "Safe Updates(rejects UPDATEs and DELETEs with no restrictions)".
It is for safe updates.
If you uncheck the above said then there are chances that you update all records instead of one record which leads to a database backup restore. there is no rollback.
I've just added COMMIT; in the end
You can enable and disable safe update option by following commands.
SET SQL_SAFE_UPDATES=1;
How can I ensure that if user-a manually updates some of his information when user-b is accessing user-a's data, that user-b accessing the information gets the correct updated information and not the old stale data for user-a.
I understand transaction are good and row level locking, I just want to make sure I am doing it correct!
When updating user-a's information I am using,
$dbc -> beginTransaction();
$dbc -> query("SELECT id FROM accounts WHERE id = " . $user['id'] . " FOR UPDATE LIMIT 1");
$q = $dbc -> prepare("UPDATE accounts SET name = ?");
$q -> execute(array($_POST['name']));
$dbc -> commit();
Using the above does this lock the user-a's data so that when user-b gets his data for user-a using,
$q = $dbc -> ("SELECT * FROM accounts WHERE id = ?");
$q -> execute(array($_GET['id']));
He will get the correct updated data? Or do I need to use a transaction when getting user-a's data for user-b??
I am a little confused by all this locking and stuff, as you can probably tell?!?
Thanks
To handle concurrency in a web site, where there is a disconnect between the client & database, it is common practice to have a column on each record that allows you to check it has not been updated since you last got it.
Either a last update date column or (my preference) an autoincremented version number (implemented via a trigger), you then simply need to check in your WHERE clause that the value you got matched the value in the record e.g:
UPDATE accounts SET name = ?, lastupdate=sysdate WHERE id = ? AND lastupdate = ?
If the lastupdate value does not match, and therfore you can't update the record, you can assume the data has been updated by someone else and handle the exception accordingly.
This works well for systems where ovelapping updates are rare.
I prefer to use triggers, as the concurrency value is maintened for you.
(the only downside is you have to requery the data if you want to re-update the same record, that is until mysql implements the RETURNING clause)
see: Handling the concurrent request while persisting in oracle database?