I have a linked server in SQL Server so when I query something, it has to be something like this:
SELECT * FROM [SERVERNAME].[DBNAME].[SCHEMA].[TABLE]
Now I have to implement this way of querying to an existing project with the servername, dbname and schema provided in my application.properties.
Is there any way to access these properties from my Mapper(xml)?
You can use properties.
With MyBatis-Spring-Boot, you can define properties in your application.properties with the prefix mybatis.configuration.variables. [1].
mybatis.configuration.variables.db_servername=YOUR_SERVER_NAME
mybatis.configuration.variables.db_dbname=YOUR_DB_NAME
mybatis.configuration.variables.db_schema=YOUR_SCHEMA
It is also possible to reference variables defined in the same application.properties.
mybatis.configuration.variables.db_servername=${servername}
mybatis.configuration.variables.db_dbname=${dbname}
mybatis.configuration.variables.db_schema=${schema}
Then you can use these variables in mappers using ${}.
SELECT * FROM [${db_servername}].[${db_dbname}].[${db_schema}].[TABLE]
Note: #{} won't work. See this FAQ entry for the difference.
[1] The doc says that the prefix is mybatis.configuration-properties., but I just tested it and it didn't work. It could be my mistake, though. I plan to investigate when I have some spare time.
Related
We're building dynamic data loading statements for Snowflake using the Python interface.
We want to create a stage at query runtime, and use that stage in a subsequent statement. Table and stage names are dynamic using bind variable.
Yet, it doens't seem like we can find the correct syntax as we tried everything on https://docs.snowflake.com/en/user-guide/python-connector-api.html
COPY INTO IDENTIFIER( %(table_name)s )(SRC, LOAD_TIME, ROW_HASH)
FROM (SELECT t.$1, CURRENT_TIMESTAMP(0), MD5(t.$1) FROM "'%(stage_name)s'" t)
PURGE = TRUE;
Is this even possible? Does it work for anyone?
Your code does not create stage as you mentioned, and you don't need create a stage, instead use table stage or user stage. The SQL below uses table stage.
You also need to change your syntax a little and use more pythonic way : f-strings
sql = f"""COPY INTO {table_name} (SRC, LOAD_TIME, ROW_HASH)
FROM (SELECT t.$1, CURRENT_TIMESTAMP(0), MD5(t.$1) FROM #%{table_name} t)
PURGE = TRUE"""
I'm trying to create a UUID id in a table with PostgreSQL. I tried with:
id uuid PRIMARY KEY DEFAULT uuid_generate_v4()
But I get:
ERROR: function uuid_generate_v4() does not exist
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
I tried with adding the schema like: id uuid PRIMARY KEY DEFAULT public.uuid_generate_v4() (as seen in a comment here)
I also checked if the extension is there (SELECT * FROM pg_available_extensions;), and yes I have it installed in the PostgreSQL database:
I read that if the Postgres is runing in --single mode, this may not work, but I don't know how to test it or if there is any way to do it.
Somebody knows how I can resolve the problem? Or any other option?
Is it a good idea to use like this:
SET DEFAULT uuid_in(md5(random()::text || now()::text)::cstring);
Because the function uuid_generate_v4 is not found, it suggests that the extension uuid-ossp is not loaded
pg_available_extensions lists the extensions available, but not necessarily loaded.
to see the list of loaded extensions query the view pg_extension as such:
select * from pg_extension;
To load the uuid-ossp extension run the following:
CREATE EXTENSION "uuid-ossp";
note: this will require super user privileges.
After the uuid-ossp extension is successfully loaded, you should see it in the pg_extension view & the function uuid_generate_v4 should be available.
In my case I needed to add the schema to the function call like this: app.uuid_generate_v4()
instead of this: uuid_generate_v4()
I found the schema for each extension by running this query:
SELECT
pge.extname,
pge.extversion,
pn.nspname AS schema
FROM pg_extension pge
JOIN pg_catalog.pg_namespace pn ON pge.extnamespace = pn."oid" ;
My code is simple:
app = Flask(__name__)
app.config.from_object('config')
db = SQLAlchemy(app)
db.metadata.reflect()
And it throws no errors. However, when I inspect the metadata after this reflection, it returns an empty immutabledict object.
The parameters in my connection string is 100% correct and the code works with non-RDS databases.
It seems to happen to others as well but I can't find a solution.
Also, I have tried to limit the reflection to specific tables using the "only" parameter in the metadata.reflect function, and this is the error I get:
sqlalchemy.exc.InvalidRequestError: Could not reflect: requested table(s) not available in mssql+pyodbc://{connection_string}: (users)
I've fixed it. The reflect() method of the SQLAlchemy class has a parameter named 'schema'. Setting this parameter, to "dbo" in my case, solved it.
I am using Flask-SQLAlchemy, which does not have the said parameter in its reflect() method. You can follow this post to gain access to that parameter and others, such as 'only'.
This error occurs when reflect is called without the schema name provided. For example, this will cause the error to happen:
metadata.reflect(only = [tableName])
It needs to be updated to use the schema of the table you are trying to reflect over like this:
metadata.reflect(schema=schemaName, only = [tableName])
You have to set schema='dbo' in parameter for reflect.
db.Model.metadata.reflect(bind=engine, schema='dbo', only=['User'])
and then create model of your table:
class User(db.Model):
__table__ = Base.metadata.tables['dbo.User']
and to access data from that table:
I'm using Cakephp 3 using sqlserver as datasource server. I am sure there's no problem with my database connection.. as home.ctp prompts that I am connected to my database.. and I'm as well using migrations plugin to create my tables.. it seems like there is no problem working with these tools. but after I bake my MVC, I only got page full of errors..
for example
$bin\cake bake all tests
there are no errors I found and MVC are in its specific folder, testController.php, testTable, etc.
and in browsers
localhost:8765\tests
but all I got is page of different errors.. Im seeing
Error: SQLSTATE[42000]: [Microsoft][SQL Server Native Client 11.0][SQL Server]Incorrect syntax near the keyword 'desc'.
SELECT * FROM (SELECT Tests.id AS [Tests__id], Tests.desc AS [Tests__desc], (ROW_NUMBER() OVER (ORDER BY (SELECT NULL))) AS [_cake_page_rownum_] FROM tests Tests) _cake_paging_ WHERE _cake_paging_._cake_page_rownum_ <= :c0
and more errors on the left side.
I assume this is because of controllers with wrong queries or queries generated by bake is for mysql only. I just wanna know how to deal with this. is there a setting I forgot to do? please advice. I am new to Cakephp, and English is not my native language, sorry if I can't explain my question properly. thanks in advance.
As already mentioned by Vishal Gajjar in the comments, you are using the reserved keyword desc for your column name, hence the error, it's not bakes fault, it's yours.
In order to be able to use such reserved words, the column name needs to be quoted properly, however CakePHP 3 doesn't auto-quote by default anymore, as it's an expensive operation.
If you insist on using reserved words, enable identifier quoting via the quoteIdentifiers option in your app.php config, or enable it manually using the autoQuoting() (enableAutoQuoting() as of CakePHP 3.4) method of the DB driver.
See also
Cookbook > Database Access & ORM > Database Basics > Identifier Quoting
Cookbook > 3.x Migration Guide > New ORM Upgrade Guide > Identifier Quoting Disabled by Default
API > \Cake\Database\Driver::autoQuoting()
API > \Cake\Database\Driver::enableAutoQuoting()
You can use this code before problematic query:
$this->Tests->connection()->driver()->autoQuoting(true);
and when you are finished you can turn auto quoting off:
$this->Tests->connection()->driver()->autoQuoting(false);
So bad performance would be only on problematic query.
Use this :
SELECT * FROM (SELECT Tests.id AS [Tests__id], Tests.[desc] AS [Tests__desc],
(ROW_NUMBER() OVER (ORDER BY (SELECT NULL))) AS [_cake_page_rownum_] FROM tests Tests) _cake_paging_
WHERE _cake_paging_._cake_page_rownum_ <= :c0
If you do use a keyword, use it in square braces [ ]
I'm a newbie to Django as well as neo4j. I'm using Django 1.4.5, neo4j 1.9.2 and neo4django 0.1.8
I've created NodeModel for a person node and indexed it on 'owner' and 'name' properties. Here is my models.py:
from neo4django.db import models as models2
class person_conns(models2.NodeModel):
owner = models2.StringProperty(max_length=30,indexed=True)
name = models2.StringProperty(max_length=30,indexed=True)
gender = models2.StringProperty(max_length=1)
parent = models2.Relationship('self',rel_type='parent_of',related_name='parents')
child = models2.Relationship('self',rel_type='child_of',related_name='children')
def __unicode__(self):
return self.name
Before I connected to Neo4j server, I set auto indexing to True and and gave indexable keys in conf/neo4j.properties file as follows:
# Autoindexing
# Enable auto-indexing for nodes, default is false
node_auto_indexing=true
# The node property keys to be auto-indexed, if enabled
node_keys_indexable=owner,name
# Enable auto-indexing for relationships, default is false
relationship_auto_indexing=true
# The relationship property keys to be auto-indexed, if enabled
relationship_keys_indexable=child_of,parent_of
I followed Neo4j: Step by Step to create an automatic index to update above file and manually create node_auto_index on neo4j server.
Below are the indexes created on neo4j server after executing syndb of django on neo4j database and manually creating auto indexes:
graph-person_conns lucene
{"to_lower_case":"true", "_blueprints:type":"MANUAL","type":"fulltext"}
node_auto_index lucene
{"_blueprints:type":"MANUAL", "type":"exact"}
As suggested in https://github.com/scholrly/neo4django/issues/123 I used connection.cypher(queries) to query the neo4j database
For Example:
listpar = connection.cypher("START no=node(*) RETURN no.owner?, no.name?",raw=True)
Above returns the owner and name of all nodes correctly. But when I try to query on indexed properties instead of 'number' or '*', as in case of:
listpar = connection.cypher("START no=node:node_auto_index(name='s2') RETURN no.owner?, no.name?",raw=True)
Above gives 0 rows.
listpar = connection.cypher("START no=node:graph-person_conns(name='s2') RETURN no.owner?, no.name?",raw=True)
Above gives
Exception Value:
Error [400]: Bad Request. Bad request syntax or unsupported method.
Invalid data sent: (' expected but-' found after graph
I tried other strings like name, person_conns instead of graph-person_conns but each time it gives error that the particular index does not exist. Am I doing a mistake while adding indexes?
My project mainly depends on filtering the nodes based on properties, so this part is really essential. Any pointers or suggestions would be appreciated. Thank you.
This is my first post on stackoverflow. So in case of any missing information or confusing statements please be patient. Thank you.
UPDATE:
Thank you for the help. For the benefit of others I would like to give example of how to use cypher queries to traverse/find shortest path between two nodes.
from neo4django.db import connection
results = connection.cypher("START source=node:`graph-person_conns`(person_name='s2sp1'),dest=node:`graph-person_conns`(person_name='s2c1') MATCH p=ShortestPath(source-[*]->dest) RETURN extract(i in nodes(p) : i.person_name), extract(j in rels(p) : type(j))")
This is to find shortest path between nodes named s2sp1 and s2c1 on the graph. Cypher queries are really cool and help traverse nodes limiting the hops, types of relations etc.
Can someone comment on the performance of this method? Also please suggest if there are any other efficient methods to access Neo4j from Django. Thank You :)
Hm, why are you using Cypher? neo4django QuerySets work just fine for the above if you set the properties to indexed=True (or not, it'll just be slower for those).
people = person_conns.objects.filter(name='n2')
The neo4django docs have some other querying examples, as do the Django docs. Neo4django executes those queries as Cypher on the backend- you really shouldn't need to drop down to writing the Cypher yourself unless you have a very particular traversal pattern or a performance issue.
Anyway, to more directly tackle your question- the last example you used needs backticks to escape the index name, like
listpar = connection.cypher("START no=node:`graph-person_conns`(name='s2') RETURN no.owner?, no.name?",raw=True)
The first example should work. One thought- did you flip the autoindexing on before or after saving the nodes you're searching for? If after, note that you'll have to manually reindex the nodes either using the Java API or by re-setting properties on the node, since it won't have been autoindexed.
HTH, and welcome to StackOverflow!