basic example with query service

examples/basic_example_v2/README.md

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+# YDB Python SDK Example: basic_example_v2
+
+Example code demonstrating the basic YDB Python SDK operations.
+
+See the top-level [README.md](../README.md) file for instructions on running this example.

examples/basic_example_v2/__main__.py

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+# -*- coding: utf-8 -*-
+import argparse
+import basic_example
+import logging
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        description="""\033[92mYDB basic example.\x1b[0m\n""",
+    )
+    parser.add_argument("-d", "--database", help="Name of the database to use", default="/local")
+    parser.add_argument("-e", "--endpoint", help="Endpoint url to use", default="grpc://localhost:2136")
+    parser.add_argument("-p", "--path", default="")
+    parser.add_argument("-v", "--verbose", default=False, action="store_true")
+
+    args = parser.parse_args()
+
+    if args.verbose:
+        logger = logging.getLogger("ydb.pool.Discovery")
+        logger.setLevel(logging.INFO)
+        logger.addHandler(logging.StreamHandler())
+
+    basic_example.run(
+        args.endpoint,
+        args.database,
+        args.path,
+    )

examples/basic_example_v2/basic_example.py

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+# -*- coding: utf-8 -*-
+import posixpath
+import ydb
+import basic_example_data
+
+# Table path prefix allows to put the working tables into the specific directory
+# inside the YDB database. Putting `PRAGMA TablePathPrefix("some/path")`
+# at the beginning of the query allows to reference the tables through
+# their names "under" the specified directory.
+#
+# TablePathPrefix has to be defined as an absolute path, which has to be started
+# with the current database location.
+#
+# https://ydb.tech/ru/docs/yql/reference/syntax/pragma#table-path-prefix
+
+DropTablesQuery = """PRAGMA TablePathPrefix("{}");
+DROP TABLE IF EXISTS series;
+DROP TABLE IF EXISTS seasons;
+DROP TABLE IF EXISTS episodes;
+"""
+
+FillDataQuery = """PRAGMA TablePathPrefix("{}");
+
+DECLARE $seriesData AS List<Struct<
+    series_id: Int64,
+    title: Utf8,
+    series_info: Utf8,
+    release_date: Date>>;
+
+DECLARE $seasonsData AS List<Struct<
+    series_id: Int64,
+    season_id: Int64,
+    title: Utf8,
+    first_aired: Date,
+    last_aired: Date>>;
+
+DECLARE $episodesData AS List<Struct<
+    series_id: Int64,
+    season_id: Int64,
+    episode_id: Int64,
+    title: Utf8,
+    air_date: Date>>;
+
+REPLACE INTO series
+SELECT
+    series_id,
+    title,
+    series_info,
+    release_date
+FROM AS_TABLE($seriesData);
+
+REPLACE INTO seasons
+SELECT
+    series_id,
+    season_id,
+    title,
+    first_aired,
+    last_aired
+FROM AS_TABLE($seasonsData);
+
+REPLACE INTO episodes
+SELECT
+    series_id,
+    season_id,
+    episode_id,
+    title,
+    air_date
+FROM AS_TABLE($episodesData);
+"""
+
+
+def fill_tables_with_data(pool: ydb.QuerySessionPool, path: str):
+    print("\nFilling tables with data...")
+
+    query = FillDataQuery.format(path)
+
+    pool.execute_with_retries(
+        query,
+        {
+            "$seriesData": (basic_example_data.get_series_data(), basic_example_data.get_series_data_type()),
+            "$seasonsData": (basic_example_data.get_seasons_data(), basic_example_data.get_seasons_data_type()),
+            "$episodesData": (basic_example_data.get_episodes_data(), basic_example_data.get_episodes_data_type()),
+        },
+    )
+
+
+def select_simple(pool: ydb.QuerySessionPool, path: str):
+    print("\nCheck series table...")
+    result_sets = pool.execute_with_retries(
+        """
+        PRAGMA TablePathPrefix("{}");
+        SELECT
+            series_id,
+            title,
+            release_date
+        FROM series
+        WHERE series_id = 1;
+        """.format(
+            path
+        ),
+    )
+    first_set = result_sets[0]
+    for row in first_set.rows:
+        print(
+            "series, id: ",
+            row.series_id,
+            ", title: ",
+            row.title,
+            ", release date: ",
+            row.release_date,
+        )
+
+    return first_set
+
+
+def upsert_simple(pool: ydb.QuerySessionPool, path: str):
+    print("\nPerforming UPSERT into episodes...")
+
+    pool.execute_with_retries(
+        """
+        PRAGMA TablePathPrefix("{}");
+        UPSERT INTO episodes (series_id, season_id, episode_id, title) VALUES (2, 6, 1, "TBD");
+        """.format(
+            path
+        )
+    )
+
+
+def select_with_parameters(pool: ydb.QuerySessionPool, path: str, series_id, season_id, episode_id):
+    result_sets = pool.execute_with_retries(
+        """
+        PRAGMA TablePathPrefix("{}");
+        SELECT
+            title,
+            air_date
+        FROM episodes
+        WHERE series_id = $seriesId AND season_id = $seasonId AND episode_id = $episodeId;
+        """.format(
+            path
+        ),
+        {
+            "$seriesId": series_id,  # could be defined implicit
+            "$seasonId": (season_id, ydb.PrimitiveType.Int64),  # could be defined via tuple
+            "$episodeId": ydb.TypedValue(episode_id, ydb.PrimitiveType.Int64),  # could be defined via special class
+        },
+    )
+
+    print("\n> select_with_parameters:")
+    first_set = result_sets[0]
+    for row in first_set.rows:
+        print("episode title:", row.title, ", air date:", row.air_date)
+
+    return first_set
+
+
+# Show usage of explicit Begin/Commit transaction control calls.
+# In most cases it's better to use transaction control settings in session.transaction
+# calls instead to avoid additional hops to YDB cluster and allow more efficient
+# execution of queries.
+def explicit_transaction_control(pool: ydb.QuerySessionPool, path: str, series_id, season_id, episode_id):
+    def callee(session: ydb.QuerySessionSync):
+        query = """
+        PRAGMA TablePathPrefix("{}");
+        UPDATE episodes
+        SET air_date = CurrentUtcDate()
+        WHERE series_id = $seriesId AND season_id = $seasonId AND episode_id = $episodeId;
+        """.format(
+            path
+        )
+
+        # Get newly created transaction id
+        tx = session.transaction(ydb.QuerySerializableReadWrite()).begin()
+
+        # Execute data query.
+        # Transaction control settings continues active transaction (tx)
+        with tx.execute(
+            query,
+            {
+                "$seriesId": (series_id, ydb.PrimitiveType.Int64),
+                "$seasonId": (season_id, ydb.PrimitiveType.Int64),
+                "$episodeId": (episode_id, ydb.PrimitiveType.Int64),
+            },
+        ) as _:
+            pass
+
+        print("\n> explicit TCL call")
+
+        # Commit active transaction(tx)
+        tx.commit()
+
+    return pool.retry_operation_sync(callee)
+
+
+def drop_tables(pool: ydb.QuerySessionPool, path: str):
+    print("\nCleaning up existing tables...")
+    pool.execute_with_retries(DropTablesQuery.format(path))
+
+
+def create_tables(pool: ydb.QuerySessionPool, path: str):
+    print("\nCreating table series...")
+    pool.execute_with_retries(
+        """
+            PRAGMA TablePathPrefix("{}");
+            CREATE table `series` (
+                `series_id` Int64,
+                `title` Utf8,
+                `series_info` Utf8,
+                `release_date` Date,
+                PRIMARY KEY (`series_id`)
+            )
+            """.format(
+            path
+        )
+    )
+
+    print("\nCreating table seasons...")
+    pool.execute_with_retries(
+        """
+            PRAGMA TablePathPrefix("{}");
+            CREATE table `seasons` (
+                `series_id` Int64,
+                `season_id` Int64,
+                `title` Utf8,
+                `first_aired` Date,
+                `last_aired` Date,
+                PRIMARY KEY (`series_id`, `season_id`)
+            )
+            """.format(
+            path
+        )
+    )
+
+    print("\nCreating table episodes...")
+    pool.execute_with_retries(
+        """
+            PRAGMA TablePathPrefix("{}");
+            CREATE table `episodes` (
+                `series_id` Int64,
+                `season_id` Int64,
+                `episode_id` Int64,
+                `title` Utf8,
+                `air_date` Date,
+                PRIMARY KEY (`series_id`, `season_id`, `episode_id`)
+            )
+            """.format(
+            path
+        )
+    )
+
+
+def is_directory_exists(driver: ydb.Driver, path: str):
+    try:
+        return driver.scheme_client.describe_path(path).is_directory()
+    except ydb.SchemeError:
+        return False
+
+
+def ensure_path_exists(driver, database, path):
+    paths_to_create = list()
+    path = path.rstrip("/")
+    while path not in ("", database):
+        full_path = posixpath.join(database, path)
+        if is_directory_exists(driver, full_path):
+            break
+        paths_to_create.append(full_path)
+        path = posixpath.dirname(path).rstrip("/")
+
+    while len(paths_to_create) > 0:
+        full_path = paths_to_create.pop(-1)
+        driver.scheme_client.make_directory(full_path)
+
+
+def run(endpoint, database, path):
+    with ydb.Driver(
+        endpoint=endpoint,
+        database=database,
+        credentials=ydb.credentials_from_env_variables(),
+    ) as driver:
+        driver.wait(timeout=5, fail_fast=True)
+
+        with ydb.QuerySessionPool(driver) as pool:
+
+            ensure_path_exists(driver, database, path)
+
+            # absolute path - prefix to the table's names,
+            # including the database location
+            full_path = posixpath.join(database, path)
+
+            drop_tables(pool, full_path)
+
+            create_tables(pool, full_path)
+
+            fill_tables_with_data(pool, full_path)
+
+            select_simple(pool, full_path)
+
+            upsert_simple(pool, full_path)
+
+            select_with_parameters(pool, full_path, 2, 3, 7)
+            select_with_parameters(pool, full_path, 2, 3, 8)
+
+            explicit_transaction_control(pool, full_path, 2, 6, 1)
+            select_with_parameters(pool, full_path, 2, 6, 1)