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What you will learn in Elasticsearch in Action, Second Edition

by Madhusudhan Konda

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Chapter by chapter

Concepts explained in this book

• ElasticsearchElasticsearch is a distributed search and analytics engine for indexing, querying, and analyzing structured and unstructured data.
• mappingAn Elasticsearch mapping specifies document fields, their data types, and their indexing and handling rules.
• replicaA duplicate copy of a primary shard maintained on a different node for redundancy and read availability.
• computer clusterA cluster is a group of connected computing nodes that operates as a coordinated Elasticsearch system for distributed processing and storage.
• document APIA single-document API is an Elasticsearch document API that performs an operation on one document at a time.
• full-text searchA full-text query analyzes text and matches documents based on linguistic terms rather than exact field values.
• relevanceRelevance is the degree to which a search result matches a query's intent or information need.
• text analyzerA text-processing component that converts language-specific text into terms suitable for indexing or searching.
• Elasticsearch indexAn Elasticsearch index is a logical collection of searchable documents distributed across shards and replicas.
• cluster nodeA running instance of Elasticsearch that participates in a cluster and performs assigned search, data, or coordination responsibilities.
• aliasAn Elasticsearch index alias is an alternate name that refers to one index or a set of indexes for search and other index operations.
• DocumentAn Elasticsearch document is a JSON record stored in an index with fields and associated metadata.
• keyword fieldA keyword field is an Elasticsearch field type that stores an entire value as a single unanalyzed term for exact matching, sorting, filtering, and aggregations.
• boolean queryA bool query is an Elasticsearch query that combines other queries through Boolean clauses to express compound search criteria.
• document idA document ID is the identifier assigned to an Elasticsearch document for addressing and retrieval.
• text analysisText analysis is the processing of text into analyzed linguistic representations to support meaning-aware search and retrieval.
• standard analyzerElasticsearch's built-in text analyzer that applies standard tokenization and related default text processing.
• search engineA search engine is software that retrieves relevant information from indexed data in response to queries.
• automatic index creationAutomatic index creation is Elasticsearch behavior that creates a missing index when an indexing request targets it.
• inverted indexAn inverted index is an index that maps each token or term to the documents containing it.
• unstructured dataUnstructured data is data that does not conform to a fixed field-based or tabular schema, such as free-form text.
• action.auto_create_indexaction.auto_create_index is an Elasticsearch setting that controls whether missing indexes may be created automatically.
• compound queryA compound query is an Elasticsearch query that combines multiple individual queries to express complex search logic.
• master nodeThe master role is the Elasticsearch node responsibility for participating in cluster-state management and cluster-management decisions.
• similarity scoringA similarity algorithm computes how closely a document matches a query to support relevance scoring.
• master-eligible nodeA master-eligible node is an Elasticsearch node assigned the master role and therefore able to vote in master elections and become the elected master.
• dynamic mappingDynamic mapping is Elasticsearch behavior that automatically derives an index mapping from the fields and values of newly indexed documents.
• snapshot repositoryA snapshot repository is a storage location that contains Elasticsearch snapshot data for backup and restoration.
• index rolloverIndex rollover is the replacement of a current Elasticsearch index with a new index while directing subsequent writes to the new index without copying existing documents.
• _search APIThe Elasticsearch HTTP endpoint for submitting search requests and retrieving matching documents or aggregation results.
• scriptAn executable expression or program embedded in an Elasticsearch request to apply conditional or computed document changes.
• request messageThe POST method is an HTTP request method used to submit data to a server for processing or resource creation.
• cluster health statusAn Elasticsearch cluster health status is a traffic-light state indicating whether the cluster's primary and replica shards are assigned and available.
• node roleA node role is a configured responsibility assigned to an Elasticsearch node, such as eligibility for master election.
• shard sizingShard sizing is the process of selecting shard capacity and count based on data volume, growth, and node resources.
• match queryA match query is an Elasticsearch query clause that analyzes supplied text and matches documents containing corresponding terms.
• node.rolesnode.roles is an Elasticsearch configuration setting containing the list of roles assigned to a node.
• update APIThe Elasticsearch Update API partially modifies an existing document and can optionally create it through upsert behavior.
• KibanaKibana is a web interface for querying Elasticsearch data and creating visualizations, dashboards, and aggregations.
• multidocument APIAn Elasticsearch API that retrieves multiple documents by their indexes and document IDs in one request.
• _create APIThe Elasticsearch _create API creates a document only when the specified document ID does not already exist.
• metric aggregationA single-value metric aggregation computes exactly one numeric value from a set of input documents.
• BM25Okapi BM25 is a probabilistic information-retrieval ranking algorithm that scores documents using term frequency, document frequency, and document-length normalization.
• CRUDCRUD is the set of operations for creating, reading, updating, and deleting stored resources.
• data typeA data type is a mapping specification that determines how a document field's values are represented, indexed, and queried in Elasticsearch.
• text fieldA text field stores analyzed textual content for full-text search.
• inverse document frequencyInverse document frequency measures how uncommon a term is across a document collection, giving rarer terms greater weight.
• term frequencyTerm frequency is the count or normalized frequency of a term's occurrences within a document or field.
• reindexingThe Elasticsearch Reindex API copies documents from a source index to a destination index, optionally applying transformations during the operation.
• schemaA schema is a formal specification of the structure, fields, types, and constraints that data must follow.
• bucket aggregationA bucket aggregation groups matching Elasticsearch documents into buckets according to specified criteria rather than computing a single metric across all documents.
• Bulk APIThe Elasticsearch _bulk API accepts multiple document indexing, update, or deletion actions in a single request.
• index lifecycle managementIndex lifecycle management is Elasticsearch functionality that automates index phases and actions based on conditions such as age, size, or document count.
• tokenizerA tokenizer is a text-analysis component that divides a character stream into discrete tokens according to specified rules.
• character filterA character filter preprocesses a character stream by removing, replacing, or adding characters before tokenization.
• _doc endpointThe _doc endpoint is an Elasticsearch document endpoint used to address, create, or replace a document within an index.
• structured dataStructured data is information organized according to a predefined schema or consistent fields and types.
• token filterA token filter is a text-analysis component that transforms, removes, or adds tokens after tokenization.
• single-node clusterA single-node cluster is an Elasticsearch cluster containing one node.
• query_string queryThe query_string query is an Elasticsearch Query DSL clause that parses a query-string expression using a strict query syntax.
• dynamic index settingA dynamic index setting is an Elasticsearch index configuration value that can be changed while the index is operational.
• standard tokenizerA standard tokenizer is a built-in Lucene text-analysis component that divides text into tokens according to predefined standard rules.
• lifecycle policyAn Elasticsearch lifecycle policy is a set of rules that controls automatic index management, lifecycle phases, transitions, and actions.
• refreshA refresh is an Elasticsearch and Lucene operation that makes buffered indexed documents searchable by creating and exposing new index segments.
• stemmingA stemmer is a language-specific text-processing component that reduces related word forms to a root word.
• boostBoosting is the technique of increasing the importance of selected query fields so matching documents receive higher relevance scores.
• _sourceThe Elasticsearch _source field contains the original JSON document stored with a search or retrieval response.
• must_not clauseA Boolean query clause in Elasticsearch that excludes documents matching its inner query.
• histogramA histogram aggregation creates buckets that represent consecutive intervals of a numerical value across documents.
• leaf queryA leaf query is an individual Elasticsearch query that evaluates document fields or values and can serve as a component of a compound query.
• segmentA Lucene index segment is a self-contained, effectively immutable structure containing indexed documents, terms, and inverted-index data.
• multi-typed fieldA multi-field is an Elasticsearch mapping definition that indexes one field value in multiple ways under separate subfields.
• primary shardA primary shard is a shard that holds the authoritative documents for part of an Elasticsearch index.
• static index settingA static index setting is an Elasticsearch index configuration value that can be set at index creation but cannot be changed while the index is operational.
• custom analyzerAn Elasticsearch analyzer assembled with user-selected character filters, tokenizer, and token filters.
• tokenizationTokenization is the process of splitting a character stream into discrete tokens according to rules such as whitespace, delimiters, or character patterns.
• vertical scalingVertical scaling increases system capacity by increasing the resources of existing machines, such as memory or CPU capacity.
• quorumA quorum is the minimum number of eligible participants whose acknowledgments are required to authorize an operation in a distributed system.
• must clauseA Boolean query clause in Elasticsearch that requires documents to match its inner query.
• horizontal scalingHorizontal scaling increases system capacity by adding more nodes or machines rather than increasing the resources of an existing node.
• snapshotA snapshot is a point-in-time backup of Elasticsearch index data and cluster state that can be restored later.
• text data typeThe text data type is an Elasticsearch mapping type for analyzed textual content used in full-text search.
• schema-less featureA schema-free feature permits data to be indexed without an explicitly defined schema.
• field-length norm algorithmA field-length norm is a document-scoring factor that adjusts term relevance according to the length of the field containing the term.
• term frequency-inverse document frequencyA term frequency–inverse document frequency algorithm ranks documents using query-term frequency in documents and term rarity across the collection.
• _slm APIThe _slm API is Elasticsearch's interface for creating, managing, and executing snapshot lifecycle policies.
• range queryA query that retrieves documents whose field values fall within specified lower and upper bounds.
• stop wordA frequently occurring word that is commonly excluded or specially handled during text analysis because it contributes little to retrieval discrimination.
• filter contextA filter context is an Elasticsearch query context in which matching determines inclusion without calculating relevance scores.
• wildcardA wildcard is a pattern symbol representing one or more variable characters when selecting index names or matching terms.
• function score queryA function score query is an Elasticsearch compound query that modifies the relevance scores of matching documents with one or more scoring functions.
• hot phaseA hot phase is an index lifecycle stage in which an index remains actively available for normal operations before later lifecycle actions occur.
• refresh intervalA refresh interval is the configured time between automatic refresh operations that make newly indexed documents searchable.
• constant_score queryAn Elasticsearch scoring mode that assigns the same score to every document matching a query.
• URI requestAn Elasticsearch search request that expresses query parameters in the request URI rather than in a Query DSL request body.
• ids queryAn ids query is an Elasticsearch query that selects documents whose identifiers match a specified set of IDs.
• geo_shape queryAn Elasticsearch geo_shape query matches documents whose indexed geographic shapes have a specified spatial relationship to a query shape.
• object data typeThe Elasticsearch object data type represents an inner JSON object whose properties are mapped as fields within a document.
• match_all queryA match_all query is an Elasticsearch query that matches every document eligible for the search.
• percolate queryAn Elasticsearch percolate query matches stored queries against a supplied document.
• pipeline aggregationA pipeline aggregation computes results from the output of other aggregations.
• filter clauseA filter clause is an Elasticsearch bool-query clause that restricts matching documents without affecting relevance scores.
• index settingA configuration property that controls operational characteristics of an Elasticsearch index, including its shards and replicas.
• geo_bounding_box queryA geo_bounding_box query retrieves documents whose geographic points or shapes intersect a rectangular geographic boundary.
• _cluster/settings endpointThe _cluster/settings endpoint is an Elasticsearch API endpoint for retrieving and modifying cluster-level settings.
• geo_point data typeA geographic coordinate represented by a latitude and longitude pair.
• fuzzy queryA fuzzy query is an Elasticsearch query that matches terms within a permitted edit distance of the supplied term.
• information retrievalSearching textual content using tokenization, matching, relevance scoring, or related linguistic analysis.
• mapping apiA mapping API is an Elasticsearch API for defining how index fields are mapped and analyzed.
• match_phrase queryA match_phrase query is an Elasticsearch query that finds documents containing a sequence of terms in the specified order.
• distance_feature queryAn Elasticsearch query that increases the relevance scores of documents whose date or geographic-point values are closer to a specified origin within a specified pivot distance.
• scripted updateA scripted update is a document modification whose changes are computed by an executable script and may depend on conditions.
• document typeA document type is a legacy Elasticsearch classification for documents sharing a data shape within an index.
• typeless endpointA typeless endpoint is an Elasticsearch URL that addresses documents without including a legacy document type.
• max token lengthA tokenizer configuration setting that specifies the maximum number of characters permitted in a token before it is split.
• geo_distance queryA geo_distance query retrieves documents whose geo-point or geo-shape values lie within a specified distance of a geographic point.
• settings endpointAn Elasticsearch endpoint for reading and changing index settings.
• multi_match queryA multi_match query is an Elasticsearch full-text query that searches for analyzed terms across multiple specified fields.
• date histogram aggregationA date histogram aggregation groups documents into time-based buckets according to a date interval.
• token_count data typeThe token_count data type is an Elasticsearch mapping type that stores the number of tokens produced for a field.
• disjunction max queryA disjunction max query is an Elasticsearch compound query that returns documents matching one or more subqueries and uses the highest matching score, optionally adjusted by a tie-break contribution.
• ELK stackThe Elastic Stack is a collection of data collection, processing, search, analytics, and visualization products that includes Beats, Logstash, Elasticsearch, and Kibana.
• full-text search engineA full-text search library is a software library that indexes and searches natural-language text.
• cluster allocation APICluster allocation is Elasticsearch functionality for inspecting and controlling the assignment of shards to nodes.
• split-brainA split-brain scenario is a distributed-system failure in which isolated node groups independently believe they are the authoritative cluster.
• query contextA query context is an Elasticsearch execution mode that evaluates whether documents match and how well they match, producing relevance scores.
• cluster stateCluster state is the distributed metadata maintained by Elasticsearch about cluster-wide resources, including shards, replicas, schemas, mappings, and fields.
• boosting queryA boosting query is an Elasticsearch compound query that promotes documents matching a positive query and optionally demotes documents matching a negative query by adjusting their relevance scores.
• well-known textWKT, or Well-Known Text, is a text format for representing geometric objects and their coordinates.
• logical AND operatorAn AND operator is a Boolean query operator that requires all joined terms to match.
• ctx context variableThe ctx context variable exposes the current document and update context to an Elasticsearch update script.
• PainlessPainless is Elasticsearch's scripting language for safely executing scripts within the platform.
• script parametersScript parameters are named values supplied separately from script source and made available to the script at execution time.
• edit distanceThe Levenshtein distance algorithm computes the minimum number of insertions, deletions, and substitutions needed to transform one string into another.
• stop-word removalA token filter that removes configured stop words from analyzed text.
• delete phaseA delete phase is an index lifecycle stage in which an index is removed after preceding lifecycle phases complete.
• fields objectThe fields object is a mapping configuration object that defines additional data-type representations for a field.
• configurationA configuration is a set of settings that controls the behavior and operation of a software system.
• date fieldA field that stores values interpreted as dates or times.
• fuzzinessFuzziness is a search setting that controls the permitted edit distance between a query term and matching indexed terms.
• date formatA date format specifies the textual or numeric representation that Elasticsearch accepts and interprets as a date.
• indexing apiThe Elasticsearch Index API adds or updates a document in an index.
• shard assignmentA shard assignment is the placement of an Elasticsearch shard on a cluster node.
• Dev ToolsDev Tools is Kibana's interface for entering and executing Elasticsearch requests and inspecting their results.
• schema-less structureSchemaless describes a data system that can accept documents without requiring a complete schema to be defined beforehand.
• time seriesTime-series data consists of observations associated with timestamps or time intervals, usually ordered chronologically.
• html_strip character filterThe html_strip character filter removes HTML markup from an input character stream before tokenization, optionally preserving specified tags.
• advanced searchAdvanced search provides rich results by interpreting query context and semantics and producing summaries, visualizations, or synthesized information.
• ChatGPTChatGPT is a conversational artificial-intelligence system that generates human-like text in response to user prompts.
• GPT-4GPT-4 is a generative pretrained transformer language model developed by OpenAI.
• GPT modelA generative pretrained transformer is a transformer-based neural-network architecture pretrained to generate or understand text.
• intuitive searchIntuitive search is search that accepts conversational natural-language queries and interprets their context and intent.
• personalized searchPersonalized search adapts results to an individual user's preferences, behavior, history, or context.
• _mount APIThe _mount API is an Elasticsearch interface for mounting snapshots so their contents can be searched.
• retention policyA snapshot retention policy specifies the conditions and duration governing how long snapshots remain available.
• searchable snapshotA searchable snapshot is a snapshot that can be mounted and queried as indexed data without first being fully restored.
• snapshot lifecycle policyA snapshot lifecycle policy is a configuration that specifies how Elasticsearch schedules, creates, and retains snapshots.
• fielddataFielddata is Elasticsearch’s on-heap data structure for loading text-field values to support operations such as sorting and aggregations.
• span queryA span query is an Elasticsearch positional query clause that matches terms according to their order and proximity in analyzed text.
• index configurationAn index configuration is the collection of mappings, settings, and aliases associated with an Elasticsearch index.
• sibling aggregationA sibling pipeline aggregation is a pipeline aggregation declared at the same level as the aggregation whose buckets it processes.
• synonymA synonym is an alternative word or phrase treated as semantically equivalent to another word for search or text processing.
• _rollover APIThe _rollover API is an Elasticsearch API that creates a successor index and repoints an alias to it according to rollover rules.
• calendar intervalA calendar interval is a date histogram interval interpreted according to calendar units and calendar-aware date adjustments.
• fixed intervalA fixed interval is a date histogram interval represented by a constant number of time units without calendar-aware month or year semantics.
• network.porthttp.port is an Elasticsearch configuration property that specifies the port used for HTTP client communication.
• transport.porttransport.port is an Elasticsearch configuration property that specifies the port used for inter-node transport communication.
• minimum match thresholdThe minimum_should_match setting specifies the minimum number of optional query clauses or terms that must match for a document to qualify.
• component templateA component template is a reusable Elasticsearch template fragment that can be associated with multiple composable index templates.
• percolator field typeThe percolator field type stores and indexes Elasticsearch queries so they can later be matched against documents.
• percolator indexA percolator index is an Elasticsearch index that stores queries for later matching against documents through percolation.
• analyze APIThe Elasticsearch analyze API analyzes supplied text and returns the terms and intermediate results produced by an analyzer.
• geo_shape data typeThe Elasticsearch geo_shape field type indexes geographic shapes such as points, lines, and polygons.
• LuceneApache Lucene is an open-source Java library for information retrieval and full-text search.
• zero downtimeZero downtime is continuous service availability during an operational change without application interruption.
• parent pipeline aggregationA parent pipeline aggregation operates on child aggregation output and adds results to existing buckets.
• unassigned shardAn unassigned shard is a shard that has not been allocated to an Elasticsearch node.
• search_as_you_type data typeThe Elasticsearch search_as_you_type field type indexes text and generated subfields to support autocomplete-style matching as text is entered.
• master electionA master election is the distributed coordination process of selecting a new Elasticsearch master node when the current master is unavailable.
• edge n-gram indexingAn edge n-gram is an n-gram anchored at the beginning of a token.
• n-gramAn n-gram is a contiguous sequence of a specified number of characters or words derived from text.
• jvm.optionsAn Elasticsearch configuration file containing options for the Java Virtual Machine, including heap-memory settings.
• wildcard queryAn Elasticsearch wildcard query is a term-level query that matches indexed terms using wildcard characters.
• high-disk watermarkAn Elasticsearch threshold on available disk space that controls shard allocation and signals storage pressure.
• georectangleA georectangle is a rectangular geographic boundary defined by the coordinates of its top-left and bottom-right corners.
• nested data typeThe Elasticsearch nested field type indexes each object in an array independently while preserving relationships among that object's fields.
• index splittingIndex splitting is the Elasticsearch operation of creating a new index with more primary shards and copying data from an existing index into it.
• _snapshot APIThe _snapshot API is an Elasticsearch REST API for creating, managing, and restoring snapshots in snapshot repositories.
• _update_by_queryThe _update_by_query API operation finds documents matching a query and applies updates to them.
• recallIn information retrieval, recall is the proportion of all relevant documents that are retrieved.
• index lifecycle phaseAn index lifecycle phase is a stage in an index lifecycle during which specified actions may be executed according to defined conditions.
• non-text fieldA non-text field stores values as structured, non-tokenized data rather than as analyzed full-text content.
• LogstashLogstash is an open-source data-processing engine that extracts, transforms, enriches, and routes event data between sources and destinations.
• elasticsearch.ymlElasticsearch's YAML configuration file for cluster, node, path, network, and security settings.
• document countdoc_count is the Elasticsearch aggregation response property containing the number of documents in a bucket.
• join data typeThe join data type is an Elasticsearch field type that represents parent-child relationships between documents in the same index.
• geospatial queryGeospatial search retrieves data according to geographic locations, shapes, distances, or spatial relationships.
• boost factorA numeric multiplier that increases the contribution of a field to a document's relevance score.
• keyword queryA search query is a request that evaluates query criteria against indexed documents to retrieve matching results.
• text highlightingHighlighting is the presentation of matching portions of returned text with markup or visual emphasis.
• explain flagAn Elasticsearch search request option that causes the response to include details about how a document's relevance score was derived.
• index shrinkingIndex shrinking is the Elasticsearch operation that creates a new index with fewer shards than a source index while preserving its documents.

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