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* Adding tests for renaming columns * Adding serialization tests for alter additions * Implementing list pagination * Adding truncation * Adding pagination tests * Adding a readme update * Cleaning up the implementation of timeuuid test records to prevent race conditions * Adding order iterator tests * Adding pagination that can deal explicitly with collections * Adding better docs for select queries
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| ### Select queries | ||
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| This explores all the various `SELECT` functionality in CQL as described in the official reference [here](http://cassandra.apache.org/doc/latest/cql/dml.html#select). | ||
| Phantom aims to provide a 100% mapping with all the latest CQL features, but if you find anything that you need missing, | ||
| please help us by reporting it through GitHub issues. | ||
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| #### Pre-requisites and setup. | ||
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| To better explain the document to follow, it is easier if we reach common ground by refering to the same Cassandra table. | ||
| The below example is a simple Cassandra table with a more complex key that allows us to explore all the features of phantom | ||
| and demonstrate the available select API. | ||
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| We will create a `AnalyticsEntries` table, where we hold information about a car's state over time for 2 properties we | ||
| care about, namely the `velocity` and `tirePressure`. We leverage the `TimeUUID` Cassandra type to store information | ||
| about timestamps, order the logs we receive in descending order(most recent record first), and prevent any colissions. | ||
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| If we would just use a timestamp type, if we were to receive two logs for the same car at the exact same timestamp, | ||
| the entries would override each other in Cassandra, because in effect they would have the same partition key | ||
| and the same clustering key, so the whole primary key would be identical. | ||
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| ```scala | ||
| import com.outworkers.phantom.dsl._ | ||
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| case class CarMetric( | ||
| car: UUID, | ||
| id: UUID, | ||
| velocity: Double, | ||
| tirePressure: Double | ||
| ) | ||
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| abstract class AnalyticsEntries extends CassandraTable[AnalyticsEntries, CarMetric] with RootConnector { | ||
| object car extends UUIDColumn(this) with PartitionKey | ||
| object id extends TimeUUIDColumn(this) with ClusteringOrder with Descending | ||
| object velocity extends DoubleColumn(this) | ||
| object tirePressure extends DoubleColumn(this) | ||
| } | ||
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| ``` | ||
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| #### Available query methods. | ||
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| The following is the list of available query methods on a select, and it can be used to leverage standard `SELECT` functionality | ||
| in various ways. | ||
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| | Method name | Return type | Purpose | | ||
| | =========== | =========== | ======= | | ||
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| ##### | ||
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| #### Paginating results by leveraging paging states and automated Cassandra pagination. | ||
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| There are situations where you can not retrieve a whole list of results in a single go, and for that reason | ||
| Cassandra offers paging states and automated pagination. Phantom makes that functionality available through a set of overloaded | ||
| methods called `paginateRecord`. |
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phantom-dsl/src/main/scala/com/outworkers/phantom/builder/ops/Alteration.scala
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| /* | ||
| * Copyright 2013 - 2017 Outworkers Ltd. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.outworkers.phantom.builder.ops | ||
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| import java.nio.ByteBuffer | ||
| import java.util.UUID | ||
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| import org.joda.time.DateTime | ||
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| /** | ||
| * Typeclass used to prevent invalid type alterations at compile time. | ||
| * Cassandra only allows for specific changes of column types using ALTER Query | ||
| * which means we need to somehow enforce the existing mechanism. | ||
| * | ||
| * We do so by requesting compile time implicit evidence that any type alteration must supply, | ||
| * e.g. that Source and Target have a predefined allowed alteration. | ||
| * | ||
| * The list of allowed ops is found here: [[[https://docs.datastax.com/en/cql/3.1/cql/cql_reference/alter_table_r.html]]. | ||
| * | ||
| * @tparam Source The source type of the column. | ||
| * @tparam Target The target type of the column. | ||
| */ | ||
| sealed trait Alteration[Source, Target] | ||
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| trait Alterations { | ||
| implicit object IntToVarint extends Alteration[Int, BigInt] | ||
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| implicit object TimeUUIDToVarint extends Alteration[UUID, UUID] | ||
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| implicit object DoubleToBlob extends Alteration[Double, ByteBuffer] | ||
| implicit object IntToBlob extends Alteration[Int, ByteBuffer] | ||
| implicit object TimestampToBlob extends Alteration[DateTime, ByteBuffer] | ||
| implicit object UUIDToBlob extends Alteration[UUID, ByteBuffer] | ||
| } |
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