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DOCSP-9567 crud query (#68)
* added CRUD > Specify a Query
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‎source/fundamentals/crud.txt

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/fundamentals/crud/read-operations
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/fundamentals/crud/write-operations
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/fundamentals/crud/query-document
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CRUD (Create, Read, Update, Delete) operations enable you to work with
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data stored in MongoDB.

‎source/fundamentals/crud/query-document.txt

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===============
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Specify a Query
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===============
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.. default-domain:: mongodb
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.. contents:: On this page
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:local:
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:backlinks: none
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:depth: 1
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:class: singlecol
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Overview
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--------
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Most CRUD operations allow you to narrow the set of matched documents by
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specifying matching criteria in a **query document**. Query documents
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contain one or more query operators that apply to specific fields which
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determine which documents to include in the result set.
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In this page, we cover the following query operators with
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examples on how to use them:
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- :ref:`Comparison Operators <query-comparison>`
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- :ref:`Logical Operators <query-logical>`
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- :ref:`Array Operators <query-arrays>`
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- :ref:`Element Operators <query-elements>`
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- :ref:`Evaluation Operators <query-evaluation>`
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The examples in this guide use the following documents in the
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``paint_purchases`` collection:
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.. code-block:: json
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{ "_id": 1, "color": "red", "qty": 9, "vendor": ["A", "E"] }
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{ "_id": 2, "color": "purple", "qty": 8, "vendor": ["B", "D", "F"], "rating": 5 }
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{ "_id": 3, "color": "blue", "qty": 5, "vendor": ["A", "E"] }
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{ "_id": 4, "color": "white", "qty": 6, "vendor": ["D"], "rating": 9 }
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{ "_id": 5, "color": "yellow", "qty": 4, "vendor": ["A", "B"] }
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{ "_id": 6, "color": "pink", "qty": 3, "vendor": ["C"] }
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{ "_id": 7, "color": "green", "qty": 8, "vendor": ["C", "E"], "rating": 7 }
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{ "_id": 8, "color": "black", "qty": 7, "vendor": ["A", "C", "D"] }
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.. _query-comparison:
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Comparison Operators
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--------------------
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Comparison operators query data based on comparisons with values in a
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collection. Common comparison operators include ``gt()`` for "greater
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than" comparisons, ``lte()`` for "less than or equal to" comparisons,
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and ``ne()`` for "not equal to " comparisons.
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The following example uses the ``Filters.gt()`` method to match all
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documents where the value of ``qty`` is greater than ``7`` in the
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``paint_purchases`` collection:
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.. literalinclude:: /includes/fundamentals/code-snippets/Query.java
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:language: java
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:dedent:
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:start-after: begin comparisonFilter
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:end-before: end comparisonFilter
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The following shows the output of the query using the operator specified
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above:
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.. code-block:: json
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:copyable: false
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{ "_id": 1, "color": "red", "qty": 9, "vendor": ["A", "E"] }
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{ "_id": 2, "color": "purple", "qty": 8, "vendor": ["B", "D", "F"], "rating": 5 }
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{ "_id": 7, "color": "green", "qty": 8, "vendor": ["C", "E"], "rating": 7 }
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.. _query-logical:
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Logical Operators
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-----------------
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Logical operators query data using logic applied to the results of
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field-level operators. Common logical operators include ``and()`` where
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all operators must be true, and ``or()`` where at least one of the
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operators must be true.
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The following example uses the ``Filters.and()`` method to match
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documents where the value of ``qty`` is less than or equal to ``5`` and
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the value of ``color`` is not ``"pink"`` in the ``paint_purchases``
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collection:
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.. literalinclude:: /includes/fundamentals/code-snippets/Query.java
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:language: java
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:dedent:
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:start-after: begin logicalFilter
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:end-before: end logicalFilter
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The following shows the output of the query using the operator specified
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above:
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.. code-block:: json
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:copyable: false
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{ "_id": 3, "color": "blue", "qty": 5, "vendor": ["A", "E"] }
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{ "_id": 5, "color": "yellow", "qty": 4, "vendor": ["A", "B"] }
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.. _query-arrays:
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Array Operators
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---------------
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Array operators query data based on the value or quantity of elements in
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an array field.
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The following example uses the ``Filters.size()`` method to match
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documents where the size of ``vendor`` list is ``3`` in the
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``paint_purchases`` collection:
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.. literalinclude:: /includes/fundamentals/code-snippets/Query.java
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:language: java
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:dedent:
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:start-after: begin arrayFilter
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:end-before: end arrayFilter
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The following shows the output of the query using the operator specified
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above:
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.. code-block:: json
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:copyable: false
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{ "_id": 2, "color": "purple", "qty": 8, "vendor": ["B", "D", "F"], "rating": 5 }
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{ "_id": 8, "color": "black", "qty": 7, "vendor": ["A", "C", "D"] }
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.. _query-elements:
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Element Operators
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-----------------
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Element operators query data based on the presence or type of a field.
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The following example uses the ``Filters.exists()`` method to match
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documents that have a ``rating`` in the ``paint_purchases`` collection:
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.. literalinclude:: /includes/fundamentals/code-snippets/Query.java
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:language: java
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:dedent:
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:start-after: begin elementFilter
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:end-before: end elementFilter
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The following shows the output of the query using the operator specified
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above:
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.. code-block:: json
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:copyable: false
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{ "_id": 2, "color": "purple", "qty": 8, "vendor": ["B", "D", "F"], "rating": 5 }
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{ "_id": 4, "color": "white", "qty": 6, "vendor": ["D"], "rating": 9 }
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{ "_id": 7, "color": "green", "qty": 8, "vendor": ["C", "E"], "rating": 7 }
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.. _query-evaluation:
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Evaluation Operators
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--------------------
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Evaluation operators query data on higher level logic, like regex
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and text searches.
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The following example uses the ``Filters.regex()`` method to match
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documents that have a ``color`` ending with the letter ``"k"`` in the
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``paint_purchases`` collection:
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.. literalinclude:: /includes/fundamentals/code-snippets/Query.java
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:language: java
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:dedent:
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:start-after: begin evaluationFilter
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:end-before: end evaluationFilter
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The following shows the output of the query using the operator specified
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above:
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.. code-block:: json
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:copyable: false
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{ "_id": 6, "color": "pink", "qty": 3, "vendor": ["C"] }
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{ "_id": 8, "color": "black", "qty": 7, "vendor": ["A", "C", "D"] }
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See the following documentation for more information about the operators
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in this guide:
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- :manual:`Query Operators </reference/operator/query/>`
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- :manual:`Comparison Operators </reference/operator/query-comparison/>`
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- :manual:`Logical Operators </reference/operator/query-logical/>`
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- :manual:`Array Operators </reference/operator/query-array/>`
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- :manual:`Element Operators </reference/operator/query-element/>`
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- :manual:`Evaluation Operators </reference/operator/query-evaluation/>`

‎source/includes/fundamentals/code-snippets/Query.java

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package docs;
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import com.mongodb.client.MongoClient;
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import com.mongodb.client.MongoClients;
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import com.mongodb.client.MongoCollection;
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import com.mongodb.client.MongoDatabase;
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import org.bson.Document;
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import org.bson.conversions.Bson;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import com.mongodb.client.model.Filters;
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public class Query {
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private final MongoCollection<Document> collection;
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private final MongoClient mongoClient;
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private final MongoDatabase database;
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private Query() {
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final String uri = System.getenv("DRIVER_REF_URI");
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mongoClient = MongoClients.create(uri);
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database = mongoClient.getDatabase("crudOps");
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collection = database.getCollection("query");
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}
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public static void main(String [] args){
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Query query = new Query();
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// query.preview();
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// query.setupPaintCollection();
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System.out.println("Comparison Filter:");
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query.comparisonFilter();
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System.out.println("Logical Filter:");
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query.logicalFilter();
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System.out.println("Element Filter:");
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query.elementFilter();
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System.out.println("Evaluation Filter:");
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query.evaluationFilter();
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System.out.println("Array Filter:");
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query.arrayFilter();
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}
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private void comparisonFilter(){
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// begin comparisonFilter
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Bson filter = Filters.gt("qty", 7);
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collection.find(filter).forEach(doc -> System.out.println(doc.toJson()));
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// end comparisonFilter
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}
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private void logicalFilter(){
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// begin logicalFilter
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Bson filter = Filters.and(Filters.lte("qty", 5), Filters.ne("color", "pink"));
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collection.find(filter).forEach(doc -> System.out.println(doc.toJson()));
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// end logicalFilter
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}
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private void elementFilter(){
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// begin elementFilter
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Bson filter = Filters.exists("rating");
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collection.find(filter).forEach(doc -> System.out.println(doc.toJson()));
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// end elementFilter
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}
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private void evaluationFilter(){
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// begin evaluationFilter
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Bson filter = Filters.regex("color", "k$");
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collection.find(filter).forEach(doc -> System.out.println(doc.toJson()));
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// end evaluationFilter
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}
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private void arrayFilter(){
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// begin arrayFilter
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Bson filter = Filters.size("vendor", 3);
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collection.find(filter).forEach(doc -> System.out.println(doc.toJson()));
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// end arrayFilter
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}
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private void preview(){
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// Bson filter = Filters.empty();
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// collection.find(filter).forEach(doc -> System.out.println(doc.toJson()));
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collection.drop();
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}
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private void setupPaintCollection() {
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List<Document> querydata = new ArrayList<>();
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Document p1 = new Document("_id", 1).append("color", "red").append("qty", 9).append("vendor", Arrays.asList("A", "E"));
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Document p2 = new Document("_id", 2).append("color", "purple").append("qty", 8).append("vendor", Arrays.asList("B", "D", "F")).append("rating", 5);
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Document p3 = new Document("_id", 3).append("color", "blue").append("qty", 5).append("vendor", Arrays.asList("A", "E"));
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Document p4 = new Document("_id", 4).append("color", "white").append("qty", 6).append("vendor", Arrays.asList("D")).append("rating", 9);
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Document p5 = new Document("_id", 5).append("color", "yellow").append("qty", 4).append("vendor", Arrays.asList("A", "B"));
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Document p6 = new Document("_id", 6).append("color", "pink").append("qty", 3).append("vendor", Arrays.asList("C"));
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Document p7 = new Document("_id", 7).append("color", "green").append("qty", 8).append("vendor", Arrays.asList("C", "E")).append("rating", 7);
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Document p8 = new Document("_id", 8).append("color", "black").append("qty", 7).append("vendor", Arrays.asList("A", "C", "D"));
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querydata.add(p1);
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querydata.add(p2);
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querydata.add(p3);
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querydata.add(p4);
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querydata.add(p5);
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querydata.add(p6);
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querydata.add(p7);
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querydata.add(p8);
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collection.insertMany(querydata);
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}
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}

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