aerospike

Query Class --- `Query`

`Query`

The Query object created by calling aerospike.Client.query is used for executing queries over a secondary index of a specified set (which can be omitted or :pyNone). For queries, the :pyNone set contains those records which are not part of any named set.

The Query can (optionally) be assigned one of the ~aerospike.predicates (~aerospike.predicates.between or ~aerospike.predicates.equals) using where. A query without a predicate will match all the records in the given set, similar to a ~aerospike.Scan.

The query is invoked using either foreach or results. The bins returned can be filtered by using select.

Finally, a stream UDF may be applied with apply. It will aggregate results out of the records streaming back from the query.

Queries and Managing Queries.

select(bin1[, bin2[, bin3..]])

Set a filter on the record bins resulting from results or foreach. If a selected bin does not exist in a record it will not appear in the bins portion of that record tuple.

where(predicate)

Set a where predicate for the query, without which the query will behave similar to aerospike.Scan. The predicate is produced by one of the aerospike.predicates methods ~aerospike.predicates.equals and ~aerospike.predicates.between.

param tuple predicate: the :pytuple produced by one of the aerospike.predicates methods.

Note

Currently, you can assign at most one predicate to the query.

results([,policy [, options]]) -> list of (key, meta, bins)

Buffer the records resulting from the query, and return them as a list of records.

param dict policy: optional aerospike_query_policies.
param dict options: optional aerospike_query_options.
return: a list of aerospike_record_tuple.

import aerospike
from aerospike import predicates as p
import pprint

config = { 'hosts': [ ('127.0.0.1', 3000)]}
client = aerospike.client(config).connect()

pp = pprint.PrettyPrinter(indent=2)
query = client.query('test', 'demo')
query.select('name', 'age') # matched records return with the values of these bins
# assuming there is a secondary index on the 'age' bin of test.demo
query.where(p.equals('age', 40))
records = query.results( {'total_timeout':2000})
pp.pprint(records)
client.close()

Note

Queries require a secondary index to exist on the bin being queried.

foreach(callback[, policy [, options]])

Invoke the callback function for each of the records streaming back from the query.

param callable callback: the function to invoke for each record.
param dict policy: optional aerospike_query_policies.
param dict options: optional aerospike_query_options.

Note

A aerospike_record_tuple is passed as the argument to the callback function.

import aerospike
from aerospike import predicates as p
import pprint

config = { 'hosts': [ ('127.0.0.1', 3000)]}
client = aerospike.client(config).connect()

pp = pprint.PrettyPrinter(indent=2)
query = client.query('test', 'demo')
query.select('name', 'age') # matched records return with the values of these bins
# assuming there is a secondary index on the 'age' bin of test.demo
query.where(p.between('age', 20, 30))
names = []
def matched_names((key, metadata, bins)):
    pp.pprint(bins)
    names.append(bins['name'])

query.foreach(matched_names, {'total_timeout':2000})
pp.pprint(names)
client.close()

Note

To stop the stream return False from the callback function.

from __future__ import print_function
import aerospike
from aerospike import predicates as p

config = { 'hosts': [ ('127.0.0.1',3000)]}
client = aerospike.client(config).connect()

def limit(lim, result):
    c = [0] # integers are immutable so a list (mutable) is used for the counter
    def key_add((key, metadata, bins)):
        if c[0] < lim:
            result.append(key)
            c[0] = c[0] + 1
        else:
            return False
    return key_add

query = client.query('test','user')
query.where(p.between('age', 20, 30))
keys = []
query.foreach(limit(100, keys))
print(len(keys)) # this will be 100 if the number of matching records > 100
client.close()

apply(module, function[, arguments])

Aggregate the results using a stream UDF. If no predicate is attached to the ~aerospike.Query the stream UDF will aggregate over all the records in the specified set.

param str module: the name of the Lua module.
param str function: the name of the Lua function within the module.
param list arguments: optional arguments to pass to the function.
return: one of the supported types, int, str, float (double), list, dict (map), bytearray (bytes).

Developing Stream UDFs

Note

Assume we registered the following Lua module with the cluster as stream_udf.lua using aerospike.Client.udf_put.

local function having_ge_threshold(bin_having, ge_threshold)
    return function(rec)
        debug("group_count::thresh_filter: %s >  %s ?", tostring(rec[bin_having]), tostring(ge_threshold))
        if rec[bin_having] < ge_threshold then
            return false
        end
        return true
    end
end

local function count(group_by_bin)
  return function(group, rec)
    if rec[group_by_bin] then
      local bin_name = rec[group_by_bin]
      group[bin_name] = (group[bin_name] or 0) + 1
      debug("group_count::count: bin %s has value %s which has the count of %s", tostring(bin_name), tostring(group[bin_name]))
    end
    return group
  end
end

local function add_values(val1, val2)
  return val1 + val2
end

local function reduce_groups(a, b)
  return map.merge(a, b, add_values)
end

function group_count(stream, group_by_bin, bin_having, ge_threshold)
  if bin_having and ge_threshold then
    local myfilter = having_ge_threshold(bin_having, ge_threshold)
    return stream : filter(myfilter) : aggregate(map{}, count(group_by_bin)) : reduce(reduce_groups)
  else
    return stream : aggregate(map{}, count(group_by_bin)) : reduce(reduce_groups)
  end
end

Find the first name distribution of users in their twenties using a query aggregation:

import aerospike
from aerospike import predicates as p
import pprint

config = {'hosts': [('127.0.0.1', 3000)],
          'lua': {'system_path':'/usr/local/aerospike/lua/',
                  'user_path':'/usr/local/aerospike/usr-lua/'}}
client = aerospike.client(config).connect()

pp = pprint.PrettyPrinter(indent=2)
query = client.query('test', 'users')
query.where(p.between('age', 20, 29))
query.apply('stream_udf', 'group_count', [ 'first_name' ])
names = query.results()
# we expect a dict (map) whose keys are names, each with a count value
pp.pprint(names)
client.close()

With stream UDFs, the final reduce steps (which ties the results from the reducers of the cluster nodes) executes on the client-side. Explicitly setting the Lua user_path in the config helps the client find the local copy of the module containing the stream UDF. The system_path is constructed when the Python package is installed, and contains system modules such as aerospike.lua, as.lua, and stream_ops.lua. The default value for the Lua system_path is /usr/local/aerospike/lua.

predexp(predicates)

Set the predicate expression filters to be used by this query.

param predicates: list A list of predicates generated by the aerospike.predexp functions

import aerospike
from aerospike import predexp as predexp
query = client.query('test', 'demo')

predexps =  [
    predexp.rec_device_size(),
    predexp.integer_value(65 * 1024),
    predexp.integer_greater()
]
query.predexp(predexps)

big_records = query.results()
client.close()

execute_background([, policy])

Execute a record UDF on records found by the query in the background. This method returns before the query has completed. A UDF must have been added to the query with Query.apply .

param dict policy: optional aerospike_write_policies.
return: a job ID that can be used with aerospike.Client.job_info to track the status of the aerospike.JOB_QUERY , as it runs in the background.

import aerospike
query = client.query('test', 'demo')
query.apply('myudfs', 'myfunction', ['a', 1])
# This id can be used to monitor the progress of the background query
query_id = query.execute_background()

Query Policies

policy

A dict of optional query policies which are applicable to Query.results and Query.foreach. See aerospike_policies.

max_retries

An int. Maximum number of retries before aborting the current transaction. The initial attempt is not counted as a retry.

If max_retries is exceeded, the transaction will return error AEROSPIKE_ERR_TIMEOUT.

WARNING: Database writes that are not idempotent (such as "add") should not be retried because the write operation may be performed multiple times
if the client timed out previous transaction attempts. It's important to use a distinct write policy for non-idempotent writes which sets max_retries = 0;

Default: 0
sleep_between_retries

An int. Milliseconds to sleep between retries. Enter zero to skip sleep. Default: 0
socket_timeout

An int. Socket idle timeout in milliseconds when processing a database command.

If socket_timeout is not zero and the socket has been idle for at least socket_timeout, both max_retries and total_timeout are checked. If max_retries and total_timeout are not exceeded, the transaction is retried.

If both socket_timeout and total_timeout are non-zero and socket_timeout > total_timeout, then socket_timeout will be set to total_timeout. If socket_timeout is zero, there will be no socket idle limit.

Default: 30000.
total_timeout

An int. Total transaction timeout in milliseconds.

The total_timeout is tracked on the client and sent to the server along with the transaction in the wire protocol. The client will most likely timeout first, but the server also has the capability to timeout the transaction.

If total_timeout is not zero and total_timeout is reached before the transaction completes, the transaction will return error AEROSPIKE_ERR_TIMEOUT. If total_timeout is zero, there will be no total time limit.

Default: 0
deserialize

bool Should raw bytes representing a list or map be deserialized to a list or dictionary.
Set to False for backup programs that just need access to raw bytes.
Default: True
fail_on_cluster_change

bool Terminate query if cluster is in migration state. Default False

Query Options

options

A dict of optional scan options which are applicable to Query.foreach and Query.results.

nobins bool whether to return the bins portion of the aerospike_record_tuple. Default False.

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Query Class --- `Query`

`Query`

Query Policies

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Query Class --- Query

Query

Query Policies

Query Options

Query Class --- `Query`

`Query`