read() with Keysets, ranges

Question

I've started playing around with the Spanner Python client (on appengine flex), but I'm hitting a few walls when trying to reuse the doc examples. One issue I'm facing is trying to read the database:

execute_sql() returns empty sets (even with a simple 'SELECT 1' query)

with database.snapshot() as snapshot:
QUERY = ('SELECT 1')
result = snapshot.execute_sql(QUERY)
for row in result.rows:
    print(row)

read() returns a "AttributeError: 'list' object has no attribute 'to_pb'" error, whether I
- try to build the whole keyset as a dictionary
```
keyset = {'keys': ['f0_'], 
          'ranges': [{'startClosed': [], 'endClosed': [500]}], 
          'all': False}
```
- passing value lists directly
```
keyset = [0, 1, 2] 
```

and an attempt at using the Keyset() constructor tells me that spanner does not have a keyset member AttributeError: 'module' object has no attribute 'keyset'

keys = ['f0_']
ranges = spanner.keyset.KeyRange(start_closed=[], end_closed=[500])
keyset = {
    'keys': keys,
    'ranges': ranges,
    'all': False}
keyset = spanner.keyset.Keyset(keys=keys, ranges=[range])

So I'm a bit stuck, and I'm wondering whether there's something I'm doing wrong or the examples / docs need a bit of spolishing... Any help appreciated :)

ok so I've moved a tiny bit forward: was able to use the Keyset / Keyranges constructor, but I get the same result.... — Thibault Lefevre, Nov 16 '17 at 14:08
moving forward, one step at a time: I could have noticed earlier that session.read() returns a StreamedResultSet (vs. ResultSet as described in the docs). Adding .consume_all() does yield the expected result ! — Thibault Lefevre, Nov 16 '17 at 19:33

score 1 · Answer 1 · answered Dec 06 '17 at 07:26

Sorry for the late response, but you can use the KeyRange and Keyset like so. Also, .consume_all() is likely to be private in the future. You should instead use list to get the answers that you want.

...
range = spanner.KeyRange(start_closed=[START], end_closed=[END])
keyset = spanner.KeySet(ranges=(closed_closed,))
rows = list(snapshot.read(self.TABLE, self.COLUMNS, keyset))
...

read() with Keysets, ranges

1 Answers1