prefect_sqlalchemy.database
¶
Tasks for querying a database with SQLAlchemy
SqlAlchemyConnector
¶
Bases: CredentialsBlock
, DatabaseBlock
Block used to manage authentication with a database.
Upon instantiating, an engine 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 could be lost.
Attributes:
Name | Type | Description |
---|---|---|
connection_info |
Union[ConnectionComponents, AnyUrl]
|
SQLAlchemy URL to create the engine; either create from components or create from a string. |
connect_args |
Optional[Dict[str, Any]]
|
The options which will be passed directly to the DBAPI's connect() method as additional keyword arguments. |
fetch_size |
int
|
The number of rows to fetch at a time. |
Example
Load stored database credentials and use in context manager:
from prefect_sqlalchemy import SqlAlchemyConnector
database_block = SqlAlchemyConnector.load("BLOCK_NAME")
with database_block:
...
Create table named customers and insert values; then fetch the first 10 rows.
from prefect_sqlalchemy import (
SqlAlchemyConnector, SyncDriver, ConnectionComponents
)
with SqlAlchemyConnector(
connection_info=ConnectionComponents(
driver=SyncDriver.SQLITE_PYSQLITE,
database="prefect.db"
)
) as database:
database.execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);",
)
for i in range(1, 42):
database.execute(
"INSERT INTO customers (name, address) VALUES (:name, :address);",
parameters={"name": "Marvin", "address": f"Highway {i}"},
)
results = database.fetch_many(
"SELECT * FROM customers WHERE name = :name;",
parameters={"name": "Marvin"},
size=10
)
print(results)
Source code in prefect_sqlalchemy/database.py
190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 |
|
Config
¶
Configuration of pydantic.
Source code in prefect_sqlalchemy/database.py
277 278 279 280 281 282 |
|
aclose
async
¶
Closes async connections and its cursors.
Source code in prefect_sqlalchemy/database.py
894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 |
|
block_initialization
¶
Initializes the engine.
Source code in prefect_sqlalchemy/database.py
295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 |
|
close
¶
Closes sync connections and its cursors.
Source code in prefect_sqlalchemy/database.py
928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 |
|
dict
¶
Convert to a dictionary.
Source code in prefect_sqlalchemy/database.py
284 285 286 287 288 289 290 291 292 293 |
|
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
|
**execution_options |
Dict[str, Any]
|
Options to pass to |
{}
|
Examples:
Create a table and insert one row into it.
from prefect_sqlalchemy import SqlAlchemyConnector
with SqlAlchemyConnector.load("MY_BLOCK") as database:
database.execute("CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);")
database.execute(
"INSERT INTO customers (name, address) VALUES (:name, :address);",
parameters={"name": "Marvin", "address": "Highway 42"},
)
Source code in prefect_sqlalchemy/database.py
789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 |
|
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 operation 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 |
**execution_options |
Dict[str, Any]
|
Options to pass to |
{}
|
Examples:
Create a table and insert two rows into it.
from prefect_sqlalchemy import SqlAlchemyConnector
with SqlAlchemyConnector.load("MY_BLOCK") as database:
database.execute("CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);")
database.execute_many(
"INSERT INTO customers (name, address) VALUES (:name, :address);",
seq_of_parameters=[
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
{"name": "Me", "address": "Myway 88"},
],
)
Source code in prefect_sqlalchemy/database.py
830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 |
|
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
|
**execution_options |
Dict[str, Any]
|
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:
Create a table, insert three rows into it, and fetch all where name is 'Me'.
from prefect_sqlalchemy import SqlAlchemyConnector
with SqlAlchemyConnector.load("MY_BLOCK") as database:
database.execute("CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);")
database.execute_many(
"INSERT INTO customers (name, address) VALUES (:name, :address);",
seq_of_parameters=[
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
{"name": "Me", "address": "Myway 88"},
],
)
results = database.fetch_all("SELECT * FROM customers WHERE name = :name", parameters={"name": "Me"})
Source code in prefect_sqlalchemy/database.py
740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 |
|
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
|
**execution_options |
Dict[str, Any]
|
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:
Create a table, insert three rows into it, and fetch two rows repeatedly.
from prefect_sqlalchemy import SqlAlchemyConnector
with SqlAlchemyConnector.load("MY_BLOCK") as database:
database.execute("CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);")
database.execute_many(
"INSERT INTO customers (name, address) VALUES (:name, :address);",
seq_of_parameters=[
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
{"name": "Me", "address": "Myway 88"},
],
)
results = database.fetch_many("SELECT * FROM customers", size=2)
print(results)
results = database.fetch_many("SELECT * FROM customers", size=2)
print(results)
Source code in prefect_sqlalchemy/database.py
684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 |
|
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
|
**execution_options |
Dict[str, Any]
|
Options to pass to |
{}
|
Returns:
Type | Description |
---|---|
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:
Create a table, insert three rows into it, and fetch a row repeatedly.
from prefect_sqlalchemy import SqlAlchemyConnector
with SqlAlchemyConnector.load("MY_BLOCK") as database:
database.execute("CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);")
database.execute_many(
"INSERT INTO customers (name, address) VALUES (:name, :address);",
seq_of_parameters=[
{"name": "Ford", "address": "Highway 42"},
{"name": "Unknown", "address": "Space"},
{"name": "Me", "address": "Myway 88"},
],
)
results = True
while results:
results = database.fetch_one("SELECT * FROM customers")
print(results)
Source code in prefect_sqlalchemy/database.py
632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 |
|
get_client
¶
Returns either an engine or connection that can be used to query from databases.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
client_type |
Literal['engine', 'connection']
|
Select from either 'engine' or 'connection'. |
required |
**get_client_kwargs |
Dict[str, Any]
|
Additional keyword arguments to pass to
either |
{}
|
Returns:
Type | Description |
---|---|
Union[Engine, AsyncEngine, Connection, AsyncConnection]
|
The authenticated SQLAlchemy engine or connection. |
Examples:
Create an engine.
from prefect_sqlalchemy import SqlalchemyConnector
sqlalchemy_connector = SqlAlchemyConnector.load("BLOCK_NAME")
engine = sqlalchemy_connector.get_client(client_type="engine")
Create a context managed connection.
from prefect_sqlalchemy import SqlalchemyConnector
sqlalchemy_connector = SqlAlchemyConnector.load("BLOCK_NAME")
with sqlalchemy_connector.get_client(client_type="connection") as conn:
...
Source code in prefect_sqlalchemy/database.py
443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 |
|
get_connection
¶
Returns a connection that can be used to query from databases.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
begin |
bool
|
Whether to begin a transaction on the connection; if True, if any operations fail, the entire transaction will be rolled back. |
True
|
**connect_kwargs |
Dict[str, Any]
|
Additional keyword arguments to pass to either
|
{}
|
Returns:
Type | Description |
---|---|
Union[Connection, AsyncConnection]
|
The SQLAlchemy Connection / AsyncConnection. |
Examples:
Create an synchronous connection as a context-managed transaction.
from prefect_sqlalchemy import SqlAlchemyConnector
sqlalchemy_connector = SqlAlchemyConnector.load("BLOCK_NAME")
with sqlalchemy_connector.get_connection(begin=False) as connection:
connection.execute("SELECT * FROM table LIMIT 1;")
Create an asynchronous connection as a context-managed transacation.
import asyncio
from prefect_sqlalchemy import SqlAlchemyConnector
sqlalchemy_connector = SqlAlchemyConnector.load("BLOCK_NAME")
async with sqlalchemy_connector.get_connection(begin=False) as connection:
asyncio.run(connection.execute("SELECT * FROM table LIMIT 1;"))
Source code in prefect_sqlalchemy/database.py
400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 |
|
get_engine
¶
Returns an authenticated engine that can be used to query from databases.
If an existing engine exists, return that one.
Returns:
Type | Description |
---|---|
Union[Engine, AsyncEngine]
|
The authenticated SQLAlchemy Engine / AsyncEngine. |
Examples:
Create an asynchronous engine to PostgreSQL using URL params.
from prefect import flow
from prefect_sqlalchemy import (
SqlAlchemyConnector, ConnectionComponents, AsyncDriver
)
@flow
def sqlalchemy_credentials_flow():
sqlalchemy_credentials = SqlAlchemyConnector(
connection_info=ConnectionComponents(
driver=AsyncDriver.POSTGRESQL_ASYNCPG,
username="prefect",
password="prefect_password",
database="postgres"
)
)
print(sqlalchemy_credentials.get_engine())
sqlalchemy_credentials_flow()
Create a synchronous engine to Snowflake using the url
kwarg.
from prefect import flow
from prefect_sqlalchemy import SqlAlchemyConnector, AsyncDriver
@flow
def sqlalchemy_credentials_flow():
url = (
"snowflake://<user_login_name>:<password>"
"@<account_identifier>/<database_name>"
"?warehouse=<warehouse_name>"
)
sqlalchemy_credentials = SqlAlchemyConnector(url=url)
print(sqlalchemy_credentials.get_engine())
sqlalchemy_credentials_flow()
Source code in prefect_sqlalchemy/database.py
326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 |
|
reset_async_connections
async
¶
Tries to close all opened connections and their results.
Examples:
Resets connections so fetch_*
methods return new results.
import asyncio
from prefect_sqlalchemy import SqlAlchemyConnector
async def example_run():
async with SqlAlchemyConnector.load("MY_BLOCK") as database:
results = await database.fetch_one("SELECT * FROM customers")
await database.reset_async_connections()
results = await database.fetch_one("SELECT * FROM customers")
asyncio.run(example_run())
Source code in prefect_sqlalchemy/database.py
599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 |
|
reset_connections
async
¶
Tries to close all opened connections and their results.
Examples:
Resets connections so fetch_*
methods return new results.
from prefect_sqlalchemy import SqlAlchemyConnector
with SqlAlchemyConnector.load("MY_BLOCK") as database:
results = database.fetch_one("SELECT * FROM customers")
database.reset_connections()
results = database.fetch_one("SELECT * FROM customers")
Source code in prefect_sqlalchemy/database.py
569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 |
|
sqlalchemy_execute
async
¶
Executes a SQL DDL or DML statement; useful for creating tables and inserting rows since this task does not return any objects.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
statement |
str
|
The statement to execute against the database. |
required |
sqlalchemy_credentials |
DatabaseCredentials
|
The credentials to use to authenticate. |
required |
params |
Optional[Union[Tuple[Any], Dict[str, Any]]]
|
The params to replace the placeholders in the query. |
None
|
Examples:
Create table named customers and insert values.
from prefect_sqlalchemy import DatabaseCredentials, AsyncDriver
from prefect_sqlalchemy.database import sqlalchemy_execute
from prefect import flow
@flow
def sqlalchemy_execute_flow():
sqlalchemy_credentials = DatabaseCredentials(
driver=AsyncDriver.SQLITE_AIOSQLITE,
database="prefect.db",
)
sqlalchemy_execute(
"CREATE TABLE IF NOT EXISTS customers (name varchar, address varchar);",
sqlalchemy_credentials,
)
sqlalchemy_execute(
"INSERT INTO customers (name, address) VALUES (:name, :address);",
sqlalchemy_credentials,
params={"name": "Marvin", "address": "Highway 42"}
)
sqlalchemy_execute_flow()
Source code in prefect_sqlalchemy/database.py
77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 |
|
sqlalchemy_query
async
¶
Executes a SQL query; useful for querying data from existing tables.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
query |
str
|
The query to execute against the database. |
required |
sqlalchemy_credentials |
DatabaseCredentials
|
The credentials to use to authenticate. |
required |
params |
Optional[Union[Tuple[Any], Dict[str, Any]]]
|
The params to replace the placeholders in the query. |
None
|
limit |
Optional[int]
|
The number of rows to fetch. Note, this parameter is
executed on the client side, i.e. passed to |
None
|
Returns:
Type | Description |
---|---|
List[Tuple[Any]]
|
The fetched results. |
Examples:
Query postgres table with the ID value parameterized.
from prefect_sqlalchemy import DatabaseCredentials, AsyncDriver
from prefect_sqlalchemy.database import sqlalchemy_query
from prefect import flow
@flow
def sqlalchemy_query_flow():
sqlalchemy_credentials = DatabaseCredentials(
driver=AsyncDriver.SQLITE_AIOSQLITE,
database="prefect.db",
)
result = sqlalchemy_query(
"SELECT * FROM customers WHERE name = :name;",
sqlalchemy_credentials,
params={"name": "Marvin"},
)
return result
sqlalchemy_query_flow()
Source code in prefect_sqlalchemy/database.py
131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 |
|