prefect_snowflake.database
¶
Module for querying against Snowflake databases.
SnowflakeConnector
¶
Bases: DatabaseBlock
Block used to manage connections with Snowflake.
Upon instantiating, a connection is created and maintained for the life of the object until the close method is called.
It is recommended to use this block as a context manager, which will automatically close the engine and its connections when the context is exited.
It is also recommended that this block is loaded and consumed within a single task or flow because if the block is passed across separate tasks and flows, the state of the block's connection and cursor will be lost.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
credentials |
The credentials to authenticate with Snowflake. |
required | |
database |
The name of the default database to use. |
required | |
warehouse |
The name of the default warehouse to use. |
required | |
schema |
The name of the default schema to use;
this attribute is accessible through |
required | |
fetch_size |
The number of rows to fetch at a time. |
required | |
poll_frequency_s |
The number of seconds before checking query. |
required |
Examples:
Load stored Snowflake connector as a context manager:
from prefect_snowflake.database import SnowflakeConnector
snowflake_connector = SnowflakeConnector.load("BLOCK_NAME")
Insert data into database and fetch results.
from prefect_snowflake.database import SnowflakeConnector
with SnowflakeConnector.load("BLOCK_NAME") as conn:
conn.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);"
)
conn.execute_many(
"INSERT INTO customers (name, address) VALUES (%(name)s, %(address)s);",
seq_of_parameters=[
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
{"name": "Me", "address": "Myway 88"},
],
)
results = conn.fetch_all(
"SELECT * FROM customers WHERE address = %(address)s",
parameters={"address": "Space"}
)
print(results)
Source code in prefect_snowflake/database.py
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|
close
¶
Closes connection and its cursors.
Source code in prefect_snowflake/database.py
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|
execute
async
¶
Executes an operation on the database. This method is intended to be used for operations that do not return data, such as INSERT, UPDATE, or DELETE. Unlike the fetch methods, this method will always execute the operation upon calling.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
operation |
str
|
The SQL query or other operation to be executed. |
required |
parameters |
Optional[Dict[str, Any]]
|
The parameters for the operation. |
None
|
cursor_type |
Type[SnowflakeCursor]
|
The class of the cursor to use when creating a Snowflake cursor. |
SnowflakeCursor
|
**execute_kwargs |
Any
|
Additional options to pass to |
{}
|
Examples:
Create table named customers with two columns, name and address.
from prefect_snowflake.database import SnowflakeConnector
with SnowflakeConnector.load("BLOCK_NAME") as conn:
conn.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);"
)
Source code in prefect_snowflake/database.py
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|
execute_many
async
¶
Executes many operations on the database. This method is intended to be used for operations that do not return data, such as INSERT, UPDATE, or DELETE. Unlike the fetch methods, this method will always execute the operations upon calling.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
operation |
str
|
The SQL query or other operation to be executed. |
required |
seq_of_parameters |
List[Dict[str, Any]]
|
The sequence of parameters for the operation. |
required |
Examples:
Create table and insert three rows into it.
from prefect_snowflake.database import SnowflakeConnector
with SnowflakeConnector.load("BLOCK_NAME") as conn:
conn.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);"
)
conn.execute_many(
"INSERT INTO customers (name, address) VALUES (%(name)s, %(address)s);",
seq_of_parameters=[
{"name": "Marvin", "address": "Highway 42"},
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
],
)
Source code in prefect_snowflake/database.py
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|
fetch_all
async
¶
Fetch all results from the database. Repeated calls using the same inputs to any of the fetch methods of this block will skip executing the operation again, and instead, return the next set of results from the previous execution, until the reset_cursors method is called.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
operation |
str
|
The SQL query or other operation to be executed. |
required |
parameters |
Optional[Dict[str, Any]]
|
The parameters for the operation. |
None
|
cursor_type |
Type[SnowflakeCursor]
|
The class of the cursor to use when creating a Snowflake cursor. |
SnowflakeCursor
|
**execute_kwargs |
Any
|
Additional options to pass to |
{}
|
Returns:
Type | Description |
---|---|
List[Tuple[Any]]
|
A list of tuples containing the data returned by the database, where each row is a tuple and each column is a value in the tuple. |
Examples:
Fetch all rows from the database where address is Highway 42.
from prefect_snowflake.database import SnowflakeConnector
with SnowflakeConnector.load("BLOCK_NAME") as conn:
conn.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);"
)
conn.execute_many(
"INSERT INTO customers (name, address) VALUES (%(name)s, %(address)s);",
seq_of_parameters=[
{"name": "Marvin", "address": "Highway 42"},
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Highway 42"},
{"name": "Me", "address": "Myway 88"},
],
)
result = conn.fetch_all(
"SELECT * FROM customers WHERE address = %(address)s",
parameters={"address": "Highway 42"},
)
print(result) # Marvin, Ford, Unknown
Source code in prefect_snowflake/database.py
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|
fetch_many
async
¶
Fetch a limited number of results from the database. Repeated calls using the same inputs to any of the fetch methods of this block will skip executing the operation again, and instead, return the next set of results from the previous execution, until the reset_cursors method is called.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
operation |
str
|
The SQL query or other operation to be executed. |
required |
parameters |
Optional[Dict[str, Any]]
|
The parameters for the operation. |
None
|
size |
Optional[int]
|
The number of results to return; if None or 0, uses the value of
|
None
|
cursor_type |
Type[SnowflakeCursor]
|
The class of the cursor to use when creating a Snowflake cursor. |
SnowflakeCursor
|
**execute_kwargs |
Any
|
Additional options to pass to |
{}
|
Returns:
Type | Description |
---|---|
List[Tuple[Any]]
|
A list of tuples containing the data returned by the database, where each row is a tuple and each column is a value in the tuple. |
Examples:
Repeatedly fetch two rows from the database where address is Highway 42.
from prefect_snowflake.database import SnowflakeConnector
with SnowflakeConnector.load("BLOCK_NAME") as conn:
conn.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);"
)
conn.execute_many(
"INSERT INTO customers (name, address) VALUES (%(name)s, %(address)s);",
seq_of_parameters=[
{"name": "Marvin", "address": "Highway 42"},
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Highway 42"},
{"name": "Me", "address": "Highway 42"},
],
)
result = conn.fetch_many(
"SELECT * FROM customers WHERE address = %(address)s",
parameters={"address": "Highway 42"},
size=2
)
print(result) # Marvin, Ford
result = conn.fetch_many(
"SELECT * FROM customers WHERE address = %(address)s",
parameters={"address": "Highway 42"},
size=2
)
print(result) # Unknown, Me
Source code in prefect_snowflake/database.py
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|
fetch_one
async
¶
Fetch a single result from the database. Repeated calls using the same inputs to any of the fetch methods of this block will skip executing the operation again, and instead, return the next set of results from the previous execution, until the reset_cursors method is called.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
operation |
str
|
The SQL query or other operation to be executed. |
required |
parameters |
Optional[Dict[str, Any]]
|
The parameters for the operation. |
None
|
cursor_type |
Type[SnowflakeCursor]
|
The class of the cursor to use when creating a Snowflake cursor. |
SnowflakeCursor
|
**execute_kwargs |
Any
|
Additional options to pass to |
{}
|
Returns:
Type | Description |
---|---|
Tuple[Any]
|
A tuple containing the data returned by the database, where each row is a tuple and each column is a value in the tuple. |
Examples:
Fetch one row from the database where address is Space.
from prefect_snowflake.database import SnowflakeConnector
with SnowflakeConnector.load("BLOCK_NAME") as conn:
conn.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);"
)
conn.execute_many(
"INSERT INTO customers (name, address) VALUES (%(name)s, %(address)s);",
seq_of_parameters=[
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
{"name": "Me", "address": "Myway 88"},
],
)
result = conn.fetch_one(
"SELECT * FROM customers WHERE address = %(address)s",
parameters={"address": "Space"}
)
print(result)
Source code in prefect_snowflake/database.py
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|
get_connection
¶
Returns an authenticated connection that can be used to query from Snowflake databases.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
**connect_kwargs |
Any
|
Additional arguments to pass to
|
{}
|
Returns:
Type | Description |
---|---|
SnowflakeConnection
|
The authenticated SnowflakeConnection. |
Examples:
from prefect_snowflake.credentials import SnowflakeCredentials
from prefect_snowflake.database import SnowflakeConnector
snowflake_credentials = SnowflakeCredentials(
account="account",
user="user",
password="password",
)
snowflake_connector = SnowflakeConnector(
database="database",
warehouse="warehouse",
schema="schema",
credentials=snowflake_credentials
)
with snowflake_connector.get_connection() as connection:
...
Source code in prefect_snowflake/database.py
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|
reset_cursors
¶
Tries to close all opened cursors.
Examples:
Reset the cursors to refresh cursor position.
from prefect_snowflake.database import SnowflakeConnector
with SnowflakeConnector.load("BLOCK_NAME") as conn:
conn.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);"
)
conn.execute_many(
"INSERT INTO customers (name, address) VALUES (%(name)s, %(address)s);",
seq_of_parameters=[
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
{"name": "Me", "address": "Myway 88"},
],
)
print(conn.fetch_one("SELECT * FROM customers")) # Ford
conn.reset_cursors()
print(conn.fetch_one("SELECT * FROM customers")) # should be Ford again
Source code in prefect_snowflake/database.py
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|
snowflake_multiquery
async
¶
Executes multiple queries against a Snowflake database in a shared session. Allows execution in a transaction.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
queries |
List[str]
|
The list of queries to execute against the database. |
required |
params |
Union[Tuple[Any], Dict[str, Any]]
|
The params to replace the placeholders in the query. |
None
|
snowflake_connector |
SnowflakeConnector
|
The credentials to use to authenticate. |
required |
cursor_type |
Type[SnowflakeCursor]
|
The type of database cursor to use for the query. |
SnowflakeCursor
|
as_transaction |
bool
|
If True, queries are executed in a transaction. |
False
|
return_transaction_control_results |
bool
|
Determines if the results of queries controlling the transaction (BEGIN/COMMIT) should be returned. |
False
|
poll_frequency_seconds |
int
|
Number of seconds to wait in between checks for run completion. |
1
|
Returns:
Type | Description |
---|---|
List[List[Tuple[Any]]]
|
List of the outputs of |
Examples:
Query Snowflake table with the ID value parameterized.
from prefect import flow
from prefect_snowflake.credentials import SnowflakeCredentials
from prefect_snowflake.database import SnowflakeConnector, snowflake_multiquery
@flow
def snowflake_multiquery_flow():
snowflake_credentials = SnowflakeCredentials(
account="account",
user="user",
password="password",
)
snowflake_connector = SnowflakeConnector(
database="database",
warehouse="warehouse",
schema="schema",
credentials=snowflake_credentials
)
result = snowflake_multiquery(
["SELECT * FROM table WHERE id=%{id_param}s LIMIT 8;", "SELECT 1,2"],
snowflake_connector,
params={"id_param": 1},
as_transaction=True
)
return result
snowflake_multiquery_flow()
Source code in prefect_snowflake/database.py
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|
snowflake_query
async
¶
Executes a query against a Snowflake database.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
query |
str
|
The query to execute against the database. |
required |
params |
Union[Tuple[Any], Dict[str, Any]]
|
The params to replace the placeholders in the query. |
None
|
snowflake_connector |
SnowflakeConnector
|
The credentials to use to authenticate. |
required |
cursor_type |
Type[SnowflakeCursor]
|
The type of database cursor to use for the query. |
SnowflakeCursor
|
poll_frequency_seconds |
int
|
Number of seconds to wait in between checks for run completion. |
1
|
Returns:
Type | Description |
---|---|
List[Tuple[Any]]
|
The output of |
Examples:
Query Snowflake table with the ID value parameterized.
from prefect import flow
from prefect_snowflake.credentials import SnowflakeCredentials
from prefect_snowflake.database import SnowflakeConnector, snowflake_query
@flow
def snowflake_query_flow():
snowflake_credentials = SnowflakeCredentials(
account="account",
user="user",
password="password",
)
snowflake_connector = SnowflakeConnector(
database="database",
warehouse="warehouse",
schema="schema",
credentials=snowflake_credentials
)
result = snowflake_query(
"SELECT * FROM table WHERE id=%{id_param}s LIMIT 8;",
snowflake_connector,
params={"id_param": 1}
)
return result
snowflake_query_flow()
Source code in prefect_snowflake/database.py
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|
snowflake_query_sync
async
¶
Executes a query in sync mode against a Snowflake database.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
query |
str
|
The query to execute against the database. |
required |
params |
Union[Tuple[Any], Dict[str, Any]]
|
The params to replace the placeholders in the query. |
None
|
snowflake_connector |
SnowflakeConnector
|
The credentials to use to authenticate. |
required |
cursor_type |
Type[SnowflakeCursor]
|
The type of database cursor to use for the query. |
SnowflakeCursor
|
Returns:
Type | Description |
---|---|
List[Tuple[Any]]
|
The output of |
Examples:
Execute a put statement.
from prefect import flow
from prefect_snowflake.credentials import SnowflakeCredentials
from prefect_snowflake.database import SnowflakeConnector, snowflake_query
@flow
def snowflake_query_sync_flow():
snowflake_credentials = SnowflakeCredentials(
account="account",
user="user",
password="password",
)
snowflake_connector = SnowflakeConnector(
database="database",
warehouse="warehouse",
schema="schema",
credentials=snowflake_credentials
)
result = snowflake_query_sync(
"put file://a_file.csv @mystage;",
snowflake_connector,
)
return result
snowflake_query_sync_flow()
Source code in prefect_snowflake/database.py
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|