def get_number_of_rows(db_engine: Engine, t: Table, sampling: int = 0):
sampling = int(sampling)
if 100 > sampling > 0:
query_total = select([func.count().label('num')]).select_from(
t.tablesample(sampling, name='alias',
seed=text('{}'.format(SEED))))
else:
query_total = select([func.count().label('num')]).select_from(alias(t))
res_t: ResultProxy = db_engine.execute(query_total)
total_rows = res_t.first()['num']
res_t.close()
return total_rows
def check_uniqueness(db_engine: Engine,
table: Table,
comb,
total_rows: int = None,
sampling: int = 0):
if comb.__len__() == 0:
return False
fields = [c for c in comb]
if not total_rows:
total_rows = get_number_of_rows(db_engine, table, sampling)
sampling = int(sampling)
if 100 > sampling > 0:
sample_t = table.tablesample(sampling,
name='alias',
seed=text('{}'.format(SEED)))
sample_fields = [sample_t.columns[fn.name] for fn in comb]
query_unique = select([func.count().label('num')]).select_from(
alias(select(sample_fields).distinct()))
res_u: ResultProxy = db_engine.execute(query_unique)
else:
if db_supports_checksum(db_engine):
checksum_method = get_checksum_function(db_engine)
query_unique = select(
[func.count(checksum_method(*fields).distinct()).label('num')])
else:
query_unique = select([func.count().label('num')]).select_from(
alias(select(fields).distinct()))
res_u: ResultProxy = db_engine.execute(query_unique)
unique_len = res_u.first()['num']
res_u.close()
return total_rows == unique_len, total_rows, unique_len
