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https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-20 23:52:08 -04:00
saarni
20f2f5b169
The TABLESAMPLE clause allows randomly selecting an approximate percentage of rows from a table. At least DB2, Microsoft SQL Server and recent Postgresql support this standard clause. Fixes: #3718 Change-Id: I3fb8b9223e12a57100df30876b461884c58d72fa Pull-request: https://github.com/zzzeek/sqlalchemy/pull/277
55 lines
1.7 KiB
Python
55 lines
1.7 KiB
Python
from sqlalchemy.testing import fixtures
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from sqlalchemy.testing import AssertsCompiledSQL, assert_raises_message
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from sqlalchemy.sql import select, func, text
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from sqlalchemy.engine import default
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from sqlalchemy import exc
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from sqlalchemy import Table, Integer, String, Column
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from sqlalchemy import tablesample
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class TableSampleTest(fixtures.TablesTest, AssertsCompiledSQL):
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__dialect__ = default.DefaultDialect(supports_native_boolean=True)
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run_setup_bind = None
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run_create_tables = None
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@classmethod
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def define_tables(cls, metadata):
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Table('people', metadata,
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Column('people_id', Integer, primary_key=True),
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Column('age', Integer),
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Column('name', String(30)))
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def test_standalone(self):
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table1 = self.tables.people
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# no special alias handling even though clause is not in the
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# context of a FROM clause
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self.assert_compile(
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tablesample(table1, 1, name='alias'),
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'people AS alias TABLESAMPLE system(:system_1)'
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)
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self.assert_compile(
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table1.tablesample(1, name='alias'),
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'people AS alias TABLESAMPLE system(:system_1)'
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)
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self.assert_compile(
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tablesample(table1, func.bernoulli(1), name='alias',
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seed=func.random()),
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'people AS alias TABLESAMPLE bernoulli(:bernoulli_1) '
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'REPEATABLE (random())'
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)
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def test_select_from(self):
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table1 = self.tables.people
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self.assert_compile(
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select([table1.tablesample(text('1'), name='alias').c.people_id]),
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'SELECT alias.people_id FROM '
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'people AS alias TABLESAMPLE system(1)'
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)
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