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  • Allow Custom Aggregates

    2021-01-11 11:44:08
    <div><p>We currently have a hard-coded white-list for aggregates. For commutative/associative aggregates, we overload the <code>sum</code> function definition. We'd like to allow people to define ...
  • 3D characterization of coarse aggregates
  • The discrete dipole approximation (DDA) method is used to calculate the scattering matrix elements and optical cross-sections for a wide variety of complex soot aggregates in random orientation at a ...
  • 1)文件名: Groups_and_Aggregates {文件名组成部分: eg表示例子 eg后面表示完成该例子的功能(没加eg后面的描述的,表示基础训练,但也需要看,要不后面涉及的基础没法做、或耽误时间) FR:表示...
  • 利用Django的ORM框架实现数据库的聚合查询。 1. 简单建一张数据表: class StatTable(models.Model): keyword = models.CharField(max_length=255, default=None) ...2. 简单介绍一下aggregates: Sum:求和 C

    利用Django的ORM框架实现数据库的聚合查询。

    1. 简单建一张数据表:

    class StatTable(models.Model):
        keyword = models.CharField(max_length=255, default=None)
        ranking = models.IntegerField(default=0)
    
        class Meta:
            db_table = 'stat_table'
    

    2. 简单介绍一下aggregates:

    • Sum:求和
    • Count:返回数量
    • Avg:返回平均值
    • Max:求最大值
    • Min:求最小值
    • Variance:计算方差
    • StdDev:计算标准差

    需要导入的库:

    from django.db.models.aggregates import Sum, Count, Avg, Variance, StdDev, Max, Min
    

    例如:我要计算ranking这一列数据的平均值:

    total = StatTable.objects.all().aggregate(avg=Avg('ranking'))
    print(total['avg'])
    

    例如:我想计算ranking的平均值,总和,数量,可以这样子写:

    total = StatTable.objects.all().aggregate(Sum('ranking'), Count('ranking'), Avg('ranking'))
    print(total)
    

    例如:我想计算ranking的最大值、最小值:

    total = StatTable.objects.all().aggregate(Max('ranking'), Min('ranking'))
    print(total)
    

    例如:我想计算ranking的方差和标准差:

    total = StatTable.objects.all().aggregate(StdDev('ranking'), Variance('ranking'))
    print(total)
    

    默认返回总体方差,如果有参数sample=True,返回值将是样本方差。

    展开全文
  • During the mass formation of aggregates of molecules in a gelatin film dyed with the mixture of chrysophenine and acridine yellow dyes, photo-reorientation, photo-disorientation, and photo-orientation...
  • Aggregates.NET是一个框架,可帮助开发人员将出色的和库集成在一起。 该库包含用于帮助创建和管理域驱动的设计对象(例如聚合,实体,值对象等)的代码。到目前为止,该框架不是唯一的选择,其他库包括: 该项目...
  • 文章目录简介根据实际物理资源创建Host Aggregates在具有相同物理特性的 computes 节点上创建 Host Aggregate设置 metadata设置flavor extra_specs参数添加过滤规则根据实际的用户需求创建 Host Aggregates创建 Host...

    OpenStack 中如何应用 Host Aggregates 来更有效地分配硬件资源

    简介

    本文将要介绍如何应用 OpenStack 中 Host Aggregates 的机制来更为有效地分配 nova computes 节点上的硬件资源,从而达到 OpenStack 的用户能够合理地选择特定的 computes 节点,来创建符合自己需求的虚拟机。Host Aggregates 最先出现在 OpenStack Grizzly 的版本中,是在 OpenStack 的 Regions 和 Availability Zones 之后被提出来,并建立于 Availability Zones 基础之上更进一步划分 computes 节点物理资源的一种机制。

    Host Aggregates 与 Availability Zones 定义上的区别
    Availability Zones 通常是对 computes 节点上的资源在小的区域内进行逻辑上的分组和隔离。例如在同一个数据中心,我们可以将 Availability Zones 规划到不同的机房,或者在同一机房的几个相邻的机架,从而保障如果某个 Availability Zone 的节点发生故障(如供电系统或网络),而不影响其他的 Availability Zones 上节点运行的虚拟机,通过这种划分来提高 OpenStack 的可用性。目前 OpenStack 默认的安装是把所有的 computes 节点划分到 nova 的 Availability Zone 上,但我们可以通过对 nova.conf 文件的配置来定义不同的 Availability zones。

    Host Aggregates 是在 Availability Zones 的基础上更进一步地进行逻辑的分组和隔离。例如我们可以根据不同的 computes 节点的物理硬件配置将具有相同共性的物理资源规划在同一 Host Aggregate 之下,或者根据用户的具体需求将几个 computes 节点规划在具有相同用途的同一 Host Aggregate 之下,通过这样的划分有利于提高 OpenStack 资源的使用效率。Host Aggregates 可以通过 nova client 或 API 来创建和配置。下面以 nova client 的命令行方式来配置 Host Aggregates。

    根据实际物理资源创建Host Aggregates

    在具有相同物理特性的 computes 节点上创建 Host Aggregate

    比如下面将具有高内存的 computes 节点规划为一组,并将 Host Aggregate 命名为"high-memory-agg"

    [root@controller ~]# nova aggregate-create high-memory-agg high-memory-az
    +----+-----------------+-------------------+-------+------------------------------------+
    | Id | Name | Availability Zone | Hosts | Metadata |
    +----+-----------------+-------------------+-------+------------------------------------+
    | 3 | high-memory-agg | high-memory-az | | 'availability_zone=high-memory-az' |
    +----+-----------------+-------------------+-------+------------------------------------+
    
    如果没有指定 Availability Zone, OpenStack 会将 Host Aggregate 建在默认的 Availability Zone 下面(如 nova),否则会根据指定的名字来判断是否创建新的 Availability Zone 或使用已经存在的 Availability Zone,同时在此之下创建 Host Aggregate。
    

    设置 metadata

    设置对应的 Host Aggregate 的 metadata,将具有高内存配置的 computes 节点的 Host aggregate 的 metadata 设置成“HW=high-memory”。
    
    [root@controller ~]# nova aggregate-set-metadata high-memory-agg HW=high-memory
    Metadata has been successfully updated for aggregate 3.
    +----+-----------------+-------------------+-------+-------------------------------------------------+
    | Id | Name | Availability Zone | Hosts | Metadata |
    +----+-----------------+-------------------+-------+--------------------------------------------- ---+
    | 3 | high-memory-agg | high-memory-az | | 'HW=high-memory', 'availability_zone=high-memory-az' |
    +----+-----------------+-------------------+-------+--------------------------------------------- ---+
    

    设置flavor extra_specs参数

    设置 flavor 的 extra_specs 的参数,保持这个参数与 Host aggregate 的 metadata 参数配置一致。
    
    [root@controller ~]# nova flavor-key High_Memory_test set HW=high-memory
    [root@controller ~]# nova flavor-show High_Memory_test
    +----------------------------+-----------------------+
    | Property | Value |
    +----------------------------+-----------------------+
    | OS-FLV-DISABLED:disabled | False |
    | OS-FLV-EXT-DATA:ephemeral | 20 |
    | disk | 60 |
    | extra_specs | {"HW": "high-memory"} |
    …
    +----------------------------+-----------------------+
    

    添加过滤规则

    将 AggregateInstanceExtraSpecsFilter 添加到所有 controller 节点的 nova.conf 配置文件的 scheduler_default_filter 项后面。
    

    根据实际的用户需求创建 Host Aggregates

    创建 Host aggregate

    根据用户需求,在一类 computes 节点上创建 Host aggregate。比如用户希望将 CPU 的 overcommit rate 为 1:5 的 computes 节点分配给开发团队使用。
    
    [root@controller ~]# nova aggregate-create dev-agg dev-az
    +----+---------+-------------------+-------+----------------------------+
    | Id | Name | Availability Zone | Hosts | Metadata |
    +----+---------+-------------------+-------+----------------------------+
    | 6 | dev-agg | dev-az | | 'availability_zone=dev-az' |
    +----+---------+-------------------+-------+----------------------------+
    
    这里的 Host Aggregate 的名称"dev-agg"需要与 Availability Zone 的名称“dev-az”建立一一对应的关系,保证以后创建虚拟机时指定 Availability Zone 会创建到对应的 Host Aggregate 下。
    

    设置metadata

    设置对应的 Host Aggregate 的 metadata,由于用户需求是 CPU 的
    
    [root@controller ~]# nova aggregate-set-metadata dev-agg cpu_allocation_ratio=5
    Metadata has been successfully updated for aggregate 6.
    +----+---------+-------------------+-------+------------------------------------------------------+
    | Id | Name | Availability Zone | Hosts | Metadata |
    +----+---------+-------------------+-------+------------------------------------------------------+
    | 6 | dev-agg | dev-az | | 'availability_zone=dev-az', 'cpu_allocation_ratio=5' |
    +----+---------+-------------------+-------+------------------------------------------------------+
    
    如果用户需要改变 memory 或者是 disk 的 overcommit rate,这里也可以设置对应的 metadata,如 ram_allocation_ratio,disk_allocation_ratio。在创建虚拟机,nova scheduler 会根据当前 Host Aggregate 的 metadata 上设定 ratio 做筛选条件来创建,如果没有找到 metadata,会使用全局的 ratio 来做筛选条件,全局的 ratio 参数配置在 nova.conf 文件里。
    

    添加filter

    将对应 filters 添加到所有 controller 节点的 nova.conf 配置文件的 scheduler_default_filter 项后面,如 AggregateCoreFilter,AggregateRamFilter 和 AggregateDiskFilter。
    

    添加节点和启动虚拟机

    添加compute节点到聚合中

    将 computes 节点上的物理机添加到对应的 Host Aggregates 里。
    
    [root@controller ~]# nova aggregate-add-host high-memory-agg kvm001 
    Host kvm001 has been successfully added for aggregate 3
    +----+-----------------+-------------------+---------------------+--------------------------------------+
    | Id | Name | Availability Zone | Hosts | Metadata |
    +----+-----------------+-------------------+---------------------+--------------------------------------+
    | 3 | high-memory-agg | high-memory-az | 'kvm001' | 'HW=high-memory', 'availability_zone=high-memory-az'|
    +----+-----------------+-------------------+---------------------+--------------------------------------+
    [root@controller ~]# nova aggregate-add-host dev-agg kvm002
    Host kvm002 has been successfully added for aggregate 6
    +----+---------+-------------------+---------------------+--------------------------------------------+
    | Id | Name | Availability Zone | Hosts | Metadata |
    +----+---------+-------------------+---------------------+-------------------------------------------+
    | 6 | dev-agg | dev-az | 'kvm002' | 'availability_zone=dev-az', 'cpu_allocation_ratio=5' |
    +----+---------+-------------------+---------------------+------------------------------------------+
    

    重启服务

    重启所有 controller 节点上的 nova-api 服务,确保新添加到 nova.conf 的 Filters 生效。
    

    创建虚拟机

    在对应的 Host Aggregates 上创建虚拟机。
    
    [root@controller ~]# nova boot high-memory-vm --image <image-id> --flavor High_Memory_test
    由于 flavor“High_Memory_test”已经与 Host Aggregate“high-memory-agg”建立 了关联,因此新建的虚拟机“high-memory-vm”应该建在这个 Host Aggregate 下,而这个 Host aggregate 只加了一个 compute 节点“kvm001”,如果“kvm001”在资源充足的条件下,虚拟机就应该成功在此创建。
    
    [root@controller ~]# nova boot dev-vm --image <image-id> --flavor m1.medium --availability-zone dev-az
    由于在创建虚拟机“dev-vm”时指定了 availability zone“dev-az”,而且“dev-az”下只存在 Host aggregate“dev-agg”,“dev-agg”上只添加了一个 compute 节点“kvm002”,因此在“kvm002”在资源充足的条件下(CPU ratio=5), 虚拟机就应该成功在此创建。
    

    验证

    验证虚拟机以及配置的 Host Aggregate Filters 是否满足用户需求
    检查虚拟机“high-memory-vm”的状态并确定是否建在了符合需求的 compute 节点上
    
    [root@controller ~]# nova show high-memory-vm
    +--------------------------------------+----------------------------------------------------------+
    | Property | Value |
    +--------------------------------------+----------------------------------------------------------+
    | OS-DCF:diskConfig | MANUAL |
    | OS-EXT-AZ:availability_zone | high-memory-az |
    | OS-EXT-SRV-ATTR:host | kvm001 |
    | OS-EXT-SRV-ATTR:hypervisor_hostname | kvm001 |
    … |
    +--------------------------------------+----------------------------------------------------------+
    
    检查虚拟机“dev-vm”的状态并确定是否建在了符合需求的 compute 节点上
    [root@controller ~]# nova show dev-vm
    +--------------------------------------+----------------------------------------------------------+
    | Property | Value |
    +--------------------------------------+----------------------------------------------------------+
    | OS-DCF:diskConfig | MANUAL |
    | OS-EXT-AZ:availability_zone | dev-az |
    | OS-EXT-SRV-ATTR:host | kvm002 |
    | OS-EXT-SRV-ATTR:hypervisor_hostname | kvm002 |
    …
    +--------------------------------------+----------------------------------------------------------+
    
    展开全文
  • <p>aggregates (total, average etc) can now be applied to a subset or exclude a given column <p>NAN values can be replaced with a given string for all columns, or for selected calls to as_percent, as_...
  • Host aggregates 主机组 主机组是一组主机compute节点的集合,默认只开放给管理员的功能,可以通过策略配置修改访问权限 官方api介绍: Creates and manages host aggregates. An aggregate assigns metadata to ...

    Host aggregates 主机组

    主机组是一组主机compute节点的集合,默认只开放给管理员的功能,可以通过策略配置修改访问权限

    官方api介绍:

    Creates and manages host aggregates. An aggregate assigns metadata to groups of compute nodes.
    Policy defaults enable only users with the administrative role to perform operations with aggregates. 
    Cloud providers can change these permissions through policy file configuration.
    

    一. url及命令

    1. url
      标准的restful api
      /os-aggregates
      /os-aggregates/{aggregate_id}

    2. 命令

    [root@nova ~]# nova help | grep aggregate
        aggregate-create            Create a new aggregate with the specified
        aggregate-delete            Delete the aggregate.
        aggregate-list              Print a list of all aggregates.
        aggregate-show              Show details of the specified aggregate.
        aggregate-update            Update the aggregate's name and optionally
    

    二. 源码分析:

    在setup.cfg中定义如下:

    aggregates = nova.api.openstack.compute.aggregates:Aggregates
    

    Aggregates定义如下:

    class Aggregates(extensions.V21APIExtensionBase):
        """Admin-only aggregate administration."""
    
        name = "Aggregates"
        alias = ALIAS
        version = 1
    
        def get_resources(self):
            resources = [extensions.ResourceExtension(
                                                ALIAS,
                                                AggregateController(),
                                                member_actions={'action': 'POST'})]
            return resources
    

    映射到AggregateController并增加了POST 方法映射到action

    1. 列表功能映射到index, 定义如下:
        @extensions.expected_errors(())
        def index(self, req):
            """Returns a list a host aggregate's id, name, availability_zone."""
            context = _get_context(req)
            context.can(aggr_policies.POLICY_ROOT % 'index')
            aggregates = self.api.get_aggregate_list(context)
            return {'aggregates': [self._marshall_aggregate(req, a)['aggregate']
                                   for a in aggregates]}
    
    

    self.api.get_aggregate_list(context) 获取列表

    实际调用如下:

        def get_aggregate_list(self, context):
            """Get all the aggregates."""
            return objects.AggregateList.get_all(context)
    

    调用object层的AggregateList的get_all方法

    1. 创建
     @extensions.expected_errors((400, 409))
        @validation.schema(aggregates.create_v20, '2.0', '2.0')
        @validation.schema(aggregates.create, '2.1')
        def create(self, req, body):
            """Creates an aggregate, given its name and
            optional availability zone.
            """
            context = _get_context(req)
            context.can(aggr_policies.POLICY_ROOT % 'create')
            host_aggregate = body["aggregate"]
            name = common.normalize_name(host_aggregate["name"])
            avail_zone = host_aggregate.get("availability_zone")
            if avail_zone:
                avail_zone = common.normalize_name(avail_zone)
    
            try:
                aggregate = self.api.create_aggregate(context, name, avail_zone)
            except exception.AggregateNameExists as e:
                raise exc.HTTPConflict(explanation=e.format_message())
            except exception.ObjectActionError:
                raise exc.HTTPConflict(explanation=_(
                    'Not all aggregates have been migrated to the API database'))
            except exception.InvalidAggregateAction as e:
                raise exc.HTTPBadRequest(explanation=e.format_message())
    

    实际创建:

    aggregate = self.api.create_aggregate(context, name, avail_zone)

    create_aggregate定义:

    
        def create_aggregate(self, context, aggregate_name, availability_zone):
            """Creates the model for the aggregate."""
    
            aggregate = objects.Aggregate(context=context)
            aggregate.name = aggregate_name
            if availability_zone:
                aggregate.metadata = {'availability_zone': availability_zone}
            aggregate.create()
            self.scheduler_client.update_aggregates(context, [aggregate])
            return aggregate          
    

    调用object层的Aggregate类的create方法
    创建完成后self.scheduler_client.update_aggregates(context, [aggregate]) 刷新nova虚拟机调度器的数据,

    
        def create(self):
            if self.obj_attr_is_set('id'):
                raise exception.ObjectActionError(action='create',
                                                  reason='already created')
    
            # NOTE(mdoff): Once we have made it past a point where we know
            # all aggregates have been migrated, we can remove this. Ideally
            # in Ocata with a blocker migration to be sure.
            if not self._ensure_migrated(self._context):
                raise exception.ObjectActionError(
                    action='create',
                    reason='main database still contains aggregates')
    
            self._assert_no_hosts('create')
            updates = self.obj_get_changes()
            payload = dict(updates)
            if 'metadata' in updates:
                # NOTE(danms): For some reason the notification format is weird
                payload['meta_data'] = payload.pop('metadata')
            if 'uuid' not in updates:
                updates['uuid'] = uuidutils.generate_uuid()
                self.uuid = updates['uuid']
                LOG.debug('Generated uuid %(uuid)s for aggregate',
                          dict(uuid=updates['uuid']))
            compute_utils.notify_about_aggregate_update(self._context,
                                                        "create.start",
                                                        payload)
            compute_utils.notify_about_aggregate_action(
                context=self._context,
                aggregate=self,
                action=fields.NotificationAction.CREATE,
                phase=fields.NotificationPhase.START)
    
            metadata = updates.pop('metadata', None)
            db_aggregate = _aggregate_create_in_db(self._context, updates,
                                                   metadata=metadata)
            self._from_db_object(self._context, self, db_aggregate)
            payload['aggregate_id'] = self.id
            compute_utils.notify_about_aggregate_update(self._context,
                                                        "create.end",
                                                        payload)
            compute_utils.notify_about_aggregate_action(
                context=self._context,
                aggregate=self,
                action=fields.NotificationAction.CREATE,
                phase=fields.NotificationPhase.END)
    
    

    创建create函数:
    首先_ensure_migrated 校验主机是可用状态,不是delete
    _aggregate_create_in_db创建主机组数据,并在metadata中创建对应的元数据

    1. 详情接口,show:
        @extensions.expected_errors(404)
        def show(self, req, id):
            """Shows the details of an aggregate, hosts and metadata included."""
            context = _get_context(req)
            context.can(aggr_policies.POLICY_ROOT % 'show')
            try:
                aggregate = self.api.get_aggregate(context, id)
            except exception.AggregateNotFound as e:
                raise exc.HTTPNotFound(explanation=e.format_mess
    

    实际调用 get_by_id:

        def get_aggregate(self, context, aggregate_id):
            """Get an aggregate by id."""
            return objects.Aggregate.get_by_id(context, aggregate_id)            
    

    get_by_id 依据id查询资源:

    db_aggregate = _aggregate_get_from_db(context, aggregate_id)
    
    @db_api.api_context_manager.reader
    def _aggregate_get_from_db(context, aggregate_id):
        query = context.session.query(api_models.Aggregate).\
                options(joinedload('_hosts')).\
                options(joinedload('_metadata'))
        query = query.filter(api_models.Aggregate.id == aggregate_id)
    
        aggregate = query.first()
    
        if not aggregate:
            raise exception.AggregateNotFound(aggregate_id=aggregate_id)
    
        return aggregate
    
    

    该方法返回aggregates所有信息:
    包含三个表数据: aggregates, aggregate_hosts, aggregate_metadata

    1. 更新:

    (可以更新name)

        @extensions.expected_errors((400, 404, 409))
        @validation.schema(aggregates.update_v20, '2.0', '2.0')
        @validation.schema(aggregates.update, '2.1')
        def update(self, req, id, body):
            """Updates the name and/or availability_zone of given aggregate."""
            context = _get_context(req)
            context.can(aggr_policies.POLICY_ROOT % 'update')
            updates = body["aggregate"]
            if 'name' in updates:
                updates['name'] = common.normalize_name(updates['name'])
    
            try:
                aggregate = self.api.update_aggregate(context, id, updates)
            except exception.AggregateNameExists as e:
                raise exc.HTTPConflict(explanation=e.format_message())
            except exception.AggregateNotFound as e:
                raise exc.HTTPNotFound(explanation=e.format_message())
            except exception.InvalidAggregateAction as e:
                raise exc.HTTPBadRequest(explanation=e.format_message())
    
            return self._marshall_aggregate(req, aggregate)
            
            
    

    self.api.update_aggregate(context, id, updates)
    该步骤首先校验主机组id是否存在,然后更新数据进行保存
    aggregate.name = values.pop('name')可看出只能更新name
    可以更新az数据metadata
    更新完成后,刷新调度的数据

    
        def update_aggregate(self, context, aggregate_id, values):
            """Update the properties of an aggregate."""
            aggregate = objects.Aggregate.get_by_id(context, aggregate_id)
            if 'name' in values:
                aggregate.name = values.pop('name')
                aggregate.save()
            self.is_safe_to_update_az(context, values, aggregate=aggregate,
                                      action_name=AGGREGATE_ACTION_UPDATE)
            if values:
                aggregate.update_metadata(values)
                aggregate.updated_at = timeutils.utcnow()
            self.scheduler_client.update_aggregates(context, [aggregate])
            .....
    

    is_safe_to_update_az有如下处理,即是更新元数据

            if 'availability_zone' in metadata:
                if not metadata['availability_zone']:
                    msg = _("Aggregate %s does not support empty named "
                            "availability zone") % aggregate.name
                    self._raise_invalid_aggregate_exc(action_name, aggregate.id,
    

    删除,delete方法:

         
         @extensions.expected_errors((400, 404))
        def delete(self, req, id):
            """Removes an aggregate by id."""
            context = _get_context(req)
            context.can(aggr_policies.POLICY_ROOT % 'delete')
            try:
                self.api.delete_aggregate(context, id)
            except exception.AggregateNotFound as e:
                raise exc.HTTPNotFound(explanation=e.format_message())
            except exception.InvalidAggregateAction as e:
                raise exc.HTTPBadRequest(explanation=e.format_message())
      
    

    delete_aggregate首先查询主机组数据,校验存在性
    然后校验主机是否为空,为空的主机组才允许删除:

            if len(aggregate.hosts) > 0:
                msg = _("Host aggregate is not empty")
                raise exception.InvalidAggregateActionDelete(
                    aggregate_id=aggregate_id, reason=msg)
    

    然后调用aggregate.destroy() 删除数据

    destroy:

    def _aggregate_delete_from_db(context, aggregate_id):
        # Delete Metadata first
        context.session.query(api_models.AggregateMetadata).\
            filter_by(aggregate_id=aggregate_id).\
            delete()
    
        count = context.session.query(api_models.Aggregate).\
                    filter(api_models.Aggregate.id == aggregate_id).\
                    delete()
    
        if count == 0:
            raise exception.AggregateNotFound(aggregate_id=aggregate_id)
            
    

    先删除metadata数据,然后清理aggregate表数据

    展开全文
  • 详细示例进入:http://kendoui.io/examples/grid/aggregates.html KendoUI中文网:http://www.kendoui.io ...

    详细示例进入:http://kendoui.io/examples/grid/aggregates.html

     

    KendoUI中文网: http://www.kendoui.io

    转载于:https://my.oschina.net/u/2325007/blog/410601

    展开全文
  • var agg = require ( "timestream-aggregates" ) var concat = require ( "concat-stream" ) function series ( ) { return spigot ( { objectMode : true } , [ { time : 1378511041582 , speed : 1 , odometer :...
  • We report ZnO nanostrawberry aggregates (ZnO NS) structure that serves as photoanode for efficient DSSCs as it offers a large specific surface area, excellent light scattering characteristics, and low...
  • of Cube Aggregates and Data Rollup 发贴人 Jaya Tiwari 在 SAP Business Warehouse 打开 2013-7-7 9:39:58 inShare Tweet What are Cube Aggregates?   Definition ...
  • <p>There can be many related timesheet aggregates. This gives us the hint that Timesheet itself should be handled as an Aggregate Root (AR): - ...
  • django-rest-framework-aggregates 将Django模型查询集的聚合功能公开给DRF API。 要求 Python 3.6+ 的Django 1.11 + Django Rest Framework 3.5.3+ 概述 此渲染器将覆盖对api v2 .agg端点的调用的默认行为。 ...
  • openTSDB详解之Rollup and pre-aggregates

    千次阅读 2018-08-11 17:41:30
    openTSDB详解之Rollup and pre-aggregates 尽管TSDB被设计为:只要仍有存储空间的话,就会存储源头的,全部的频率数据,但是很广的时间范围中且有许多标签集合中的查询,仍然是很痛苦的。这类查询经常花费大量的...
  • 文章来自作者维护的社区微信公众号...Host Aggregates 的机制是建立于 Availability Zones 基础之上更进一步划分 computes 节点物理资源的一种机制。 什么是Region Region更像是一个地理上的概念,每个regio...
  • 本文将要介绍如何应用 OpenStack 中 Host Aggregates 的机制来更为有效地分配 nova computes 节点上的硬件资源,从而达到 OpenStack 的用户能够合理地选择特定的 computes 节点,来创建符合自己需求的虚拟机。...
  • 这篇文章有点长,如果你想同时了解aggregates和PODs(Plain Old Date),就请花点时间把这篇文章读完。如果你仅仅对aggregates感兴趣,则只需阅读第一部分就好。如果你只对PODs感兴趣,你必须首先...
  • 通过 #aggregates.sum() 实现 <tr th:each="item,index: ${consumeOrderDetailList}"> <td>[[${index.count}]]</td> <td>[[${item.orderNo}]]</td> <td>[[${item.orderNo}]...
  • Promote the Manufacture of Construction Cement Aggregates Cement is one of the most important civil engineering projects .And it is composed of the Cementing materials, aggregates and water with the ...
  • aggregate 主机管理管理 可以向主机中添加,或者移除一个主机,也可以.../os-aggregates/{aggregate_id}/action 命令行: [root@nova ~]# nova help | grep agg aggregate-add-host Add the host to the specifi...
  • Table 8-1 Requirements for Materialized Views with Aggregates If aggregate X is present, aggregate Y is required and aggregate Z is optional X Y Z COUNT(expr) -
  • -- 可以查询timescaledb_information.continuous_aggregates获取所有的聚合视图,如果要查询相关聚合处理进程的处理状态,可以查询 timescaledb_information.continuous_aggregate_stats视图。 SELECT view_name, ...
  • https://www.infoq.com/articles/microservices-aggregates-events-cqrs-part-1-richardson Key takeaways The Microservice architecture functionally decomposes an application into services, each of wh
  • //from:https://blog.russellbryant.net/2013/05/21/availability-zones-and-host-aggregates-in-openstack-compute-nova/ 写的特别清楚感觉。分享给大家 ======================================================...
  • Openstack 对于主机的分布区域的划分主要方式主要有Zones,region,以及在g版新引入的...我在这里主要介绍一种逻辑划分方式Host aggregates。  Host aggregates 是对于availability zone的进一步的细分,availabil

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