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## org.apache.lucene.index
Class IndexWriterConfig

    java.lang.Object
      org.apache.lucene.index.LiveIndexWriterConfig
          org.apache.lucene.index.IndexWriterConfig

All Implemented Interfaces:
  Cloneable

    public final class IndexWriterConfig

extends LiveIndexWriterConfig
implements Cloneable

Holds all the configuration that is used to create an `IndexWriter`. Once `IndexWriter` has been created with this object, changes to this object will not affect the `IndexWriter` instance. For that, use `LiveIndexWriterConfig` that is returned from `IndexWriter.getConfig()`.

All setter methods return `IndexWriterConfig` to allow chaining settings conveniently, for example:

     IndexWriterConfig conf = new IndexWriterConfig(analyzer);
     conf.setter1().setter2();

Since:
  3.1
See Also:
  `IndexWriter.getConfig()`

Nested Class Summary
`static class` | `IndexWriterConfig.OpenMode` Specifies the open mode for `IndexWriter`.

Field Summary
`static int` | `DEFAULT_MAX_BUFFERED_DELETE_TERMS` Disabled by default (because IndexWriter flushes by RAM usage by default).
`static int` | `DEFAULT_MAX_BUFFERED_DOCS` Disabled by default (because IndexWriter flushes by RAM usage by default).
`static int` | `DEFAULT_MAX_THREAD_STATES` The maximum number of simultaneous threads that may be indexing documents at once in IndexWriter; if more than this many threads arrive they will wait for others to finish.
`static double` | `DEFAULT_RAM_BUFFER_SIZE_MB` Default value is 16 MB (which means flush when buffered docs consume approximately 16 MB RAM).
`static int` | `DEFAULT_RAM_PER_THREAD_HARD_LIMIT_MB` Default value is 1945.
`static boolean` | `DEFAULT_READER_POOLING` Default setting for `setReaderPooling(boolean)`.
`static int` | `DEFAULT_READER_TERMS_INDEX_DIVISOR` Default value is 1.
`static int` | `DEFAULT_TERM_INDEX_INTERVAL` Default value is 32.
`static int` | `DISABLE_AUTO_FLUSH` Denotes a flush trigger is disabled.
`static long` | `WRITE_LOCK_TIMEOUT` Default value for the write lock timeout (1,000 ms).

Fields inherited from class org.apache.lucene.index.LiveIndexWriterConfig
`codec, commit, delPolicy, flushPolicy, indexerThreadPool, indexingChain, infoStream, matchVersion, mergePolicy, mergeScheduler, openMode, perThreadHardLimitMB, readerPooling, similarity, writeLockTimeout`

Constructor Summary
`IndexWriterConfig(Version matchVersion, Analyzer analyzer)` Creates a new config that with defaults that match the specified `Version` as well as the default `Analyzer`.

Method Summary
`IndexWriterConfig` | `clone()`
`Analyzer` | `getAnalyzer()` Returns the default analyzer to use for indexing documents.
`Codec` | `getCodec()` Returns the current `Codec`.
`static long` | `getDefaultWriteLockTimeout()` Returns the default write lock timeout for newly instantiated IndexWriterConfigs.
`IndexCommit` | `getIndexCommit()` Returns the `IndexCommit` as specified in `setIndexCommit(IndexCommit)` or the default, `null` which specifies to open the latest index commit point.
`IndexDeletionPolicy` | `getIndexDeletionPolicy()` Returns the `IndexDeletionPolicy` specified in `setIndexDeletionPolicy(IndexDeletionPolicy)` or the default `KeepOnlyLastCommitDeletionPolicy`/
`InfoStream` | `getInfoStream()` Returns `InfoStream` used for debugging.
`int` | `getMaxBufferedDeleteTerms()` Returns the number of buffered deleted terms that will trigger a flush of all buffered deletes if enabled.
`int` | `getMaxBufferedDocs()` Returns the number of buffered added documents that will trigger a flush if enabled.
`int` | `getMaxThreadStates()` Returns the max number of simultaneous threads that may be indexing documents at once in IndexWriter.
`IndexWriter.IndexReaderWarmer` | `getMergedSegmentWarmer()` Returns the current merged segment warmer.
`MergePolicy` | `getMergePolicy()` Returns the current MergePolicy in use by this writer.
`MergeScheduler` | `getMergeScheduler()` Returns the `MergeScheduler` that was set by `setMergeScheduler(MergeScheduler)`.
`IndexWriterConfig.OpenMode` | `getOpenMode()` Returns the `IndexWriterConfig.OpenMode` set by `setOpenMode(OpenMode)`.
`double` | `getRAMBufferSizeMB()` Returns the value set by `LiveIndexWriterConfig.setRAMBufferSizeMB(double)` if enabled.
`int` | `getRAMPerThreadHardLimitMB()` Returns the max amount of memory each `DocumentsWriterPerThread` can consume until forcefully flushed.
`boolean` | `getReaderPooling()` Returns `true` if `IndexWriter` should pool readers even if `DirectoryReader.open(IndexWriter, boolean)` has not been called.
`int` | `getReaderTermsIndexDivisor()` Returns the `termInfosIndexDivisor`.
`Similarity` | `getSimilarity()` Expert: returns the `Similarity` implementation used by this `IndexWriter`.
`int` | `getTermIndexInterval()` Returns the interval between indexed terms.
`long` | `getWriteLockTimeout()` Returns allowed timeout when acquiring the write lock.
`IndexWriterConfig` | `setCodec(Codec codec)` Set the `Codec`.
`static void` | `setDefaultWriteLockTimeout(long writeLockTimeout)` Sets the default (for any instance) maximum time to wait for a write lock (in milliseconds).
`IndexWriterConfig` | `setIndexCommit(IndexCommit commit)` Expert: allows to open a certain commit point.
`IndexWriterConfig` | `setIndexDeletionPolicy(IndexDeletionPolicy delPolicy)` Expert: allows an optional `IndexDeletionPolicy` implementation to be specified.
`IndexWriterConfig` | `setInfoStream(InfoStream infoStream)` If non-null, information about merges, deletes and a message when maxFieldLength is reached will be printed to this.
`IndexWriterConfig` | `setInfoStream(PrintStream printStream)` Convenience method that uses `PrintStreamInfoStream`
`IndexWriterConfig` | `setMaxBufferedDeleteTerms(int maxBufferedDeleteTerms)` Determines the minimal number of delete terms required before the buffered in-memory delete terms and queries are applied and flushed.
`IndexWriterConfig` | `setMaxBufferedDocs(int maxBufferedDocs)` Determines the minimal number of documents required before the buffered in-memory documents are flushed as a new Segment.
`IndexWriterConfig` | `setMaxThreadStates(int maxThreadStates)` Sets the max number of simultaneous threads that may be indexing documents at once in IndexWriter.
`IndexWriterConfig` | `setMergedSegmentWarmer(IndexWriter.IndexReaderWarmer mergeSegmentWarmer)` Set the merged segment warmer.
`IndexWriterConfig` | `setMergePolicy(MergePolicy mergePolicy)` Expert: `MergePolicy` is invoked whenever there are changes to the segments in the index.
`IndexWriterConfig` | `setMergeScheduler(MergeScheduler mergeScheduler)` Expert: sets the merge scheduler used by this writer.
`IndexWriterConfig` | `setOpenMode(IndexWriterConfig.OpenMode openMode)` Specifies `IndexWriterConfig.OpenMode` of the index.
`IndexWriterConfig` | `setRAMBufferSizeMB(double ramBufferSizeMB)` Determines the amount of RAM that may be used for buffering added documents and deletions before they are flushed to the Directory.
`IndexWriterConfig` | `setRAMPerThreadHardLimitMB(int perThreadHardLimitMB)` Expert: Sets the maximum memory consumption per thread triggering a forced flush if exceeded.
`IndexWriterConfig` | `setReaderPooling(boolean readerPooling)` By default, IndexWriter does not pool the SegmentReaders it must open for deletions and merging, unless a near-real-time reader has been obtained by calling `DirectoryReader.open(IndexWriter, boolean)`.
`IndexWriterConfig` | `setReaderTermsIndexDivisor(int divisor)` Sets the termsIndexDivisor passed to any readers that IndexWriter opens, for example when applying deletes or creating a near-real-time reader in `DirectoryReader.open(IndexWriter, boolean)`.
`IndexWriterConfig` | `setSimilarity(Similarity similarity)` Expert: set the `Similarity` implementation used by this IndexWriter.
`IndexWriterConfig` | `setTermIndexInterval(int interval)` Expert: set the interval between indexed terms.
`IndexWriterConfig` | `setWriteLockTimeout(long writeLockTimeout)` Sets the maximum time to wait for a write lock (in milliseconds) for this instance.

Methods inherited from class org.apache.lucene.index.LiveIndexWriterConfig
`toString`

Methods inherited from class java.lang.Object
`equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

### DEFAULT_TERM_INDEX_INTERVAL

    public static final int DEFAULT_TERM_INDEX_INTERVAL

  Default value is 32. Change using `setTermIndexInterval(int)`.

  See Also:
    Constant Field Values

### DISABLE_AUTO_FLUSH

    public static final int DISABLE_AUTO_FLUSH

  Denotes a flush trigger is disabled.

  See Also:
    Constant Field Values

### DEFAULT_MAX_BUFFERED_DELETE_TERMS

    public static final int DEFAULT_MAX_BUFFERED_DELETE_TERMS

  Disabled by default (because IndexWriter flushes by RAM usage by default).

  See Also:
    Constant Field Values

### DEFAULT_MAX_BUFFERED_DOCS

    public static final int DEFAULT_MAX_BUFFERED_DOCS

  Disabled by default (because IndexWriter flushes by RAM usage by default).

  See Also:
    Constant Field Values

### DEFAULT_RAM_BUFFER_SIZE_MB

    public static final double DEFAULT_RAM_BUFFER_SIZE_MB

  Default value is 16 MB (which means flush when buffered docs consume approximately 16 MB RAM).

  See Also:
    Constant Field Values

### WRITE_LOCK_TIMEOUT

    public static long WRITE_LOCK_TIMEOUT

  Default value for the write lock timeout (1,000 ms).

  See Also:
    `setDefaultWriteLockTimeout(long)`

### DEFAULT_READER_POOLING

    public static final boolean DEFAULT_READER_POOLING

  Default setting for `setReaderPooling(boolean)`.

  See Also:
    Constant Field Values

### DEFAULT_READER_TERMS_INDEX_DIVISOR

    public static final int DEFAULT_READER_TERMS_INDEX_DIVISOR

  Default value is 1. Change using `setReaderTermsIndexDivisor(int)`.

  See Also:
    Constant Field Values

### DEFAULT_RAM_PER_THREAD_HARD_LIMIT_MB

    public static final int DEFAULT_RAM_PER_THREAD_HARD_LIMIT_MB

  Default value is 1945. Change using `setRAMPerThreadHardLimitMB(int)`

  See Also:
    Constant Field Values

### DEFAULT_MAX_THREAD_STATES

    public static final int DEFAULT_MAX_THREAD_STATES

  The maximum number of simultaneous threads that may be indexing documents at once in IndexWriter; if more than this many threads arrive they will wait for others to finish. Default value is 8.

  See Also:
    Constant Field Values

Constructor Detail

### IndexWriterConfig

    public IndexWriterConfig(Version matchVersion,
                             Analyzer analyzer)

  Creates a new config that with defaults that match the specified `Version` as well as the default `Analyzer`. If matchVersion is >= `Version.LUCENE_32`, `TieredMergePolicy` is used for merging; else `LogByteSizeMergePolicy`. Note that `TieredMergePolicy` is free to select non-contiguous merges, which means docIDs may not remain monotonic over time. If this is a problem you should switch to `LogByteSizeMergePolicy` or `LogDocMergePolicy`.

Method Detail

### setDefaultWriteLockTimeout

    public static void setDefaultWriteLockTimeout(long writeLockTimeout)

  Sets the default (for any instance) maximum time to wait for a write lock (in milliseconds).

### getDefaultWriteLockTimeout

    public static long getDefaultWriteLockTimeout()

  Returns the default write lock timeout for newly instantiated IndexWriterConfigs.

  See Also:
    `setDefaultWriteLockTimeout(long)`

### clone

    public IndexWriterConfig clone()

  Overrides:
    `clone` in class `Object`

### setOpenMode

    public IndexWriterConfig setOpenMode(IndexWriterConfig.OpenMode openMode)

  Specifies `IndexWriterConfig.OpenMode` of the index.

  Only takes effect when IndexWriter is first created.

### getOpenMode

    public IndexWriterConfig.OpenMode getOpenMode()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the `IndexWriterConfig.OpenMode` set by `setOpenMode(OpenMode)`.

  Overrides:
    `getOpenMode` in class `LiveIndexWriterConfig`

### setIndexDeletionPolicy

    public IndexWriterConfig setIndexDeletionPolicy(IndexDeletionPolicy delPolicy)

  Expert: allows an optional `IndexDeletionPolicy` implementation to be specified. You can use this to control when prior commits are deleted from the index. The default policy is `KeepOnlyLastCommitDeletionPolicy` which removes all prior commits as soon as a new commit is done (this matches behavior before 2.2). Creating your own policy can allow you to explicitly keep previous "point in time" commits alive in the index for some time, to allow readers to refresh to the new commit without having the old commit deleted out from under them. This is necessary on filesystems like NFS that do not support "delete on last close" semantics, which Lucene's "point in time" search normally relies on.

  NOTE: the deletion policy cannot be null.

  Only takes effect when IndexWriter is first created.

### getIndexDeletionPolicy

    public IndexDeletionPolicy getIndexDeletionPolicy()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the `IndexDeletionPolicy` specified in `setIndexDeletionPolicy(IndexDeletionPolicy)` or the default `KeepOnlyLastCommitDeletionPolicy`/

  Overrides:
    `getIndexDeletionPolicy` in class `LiveIndexWriterConfig`

### setIndexCommit

    public IndexWriterConfig setIndexCommit(IndexCommit commit)

  Expert: allows to open a certain commit point. The default is null which opens the latest commit point.

  Only takes effect when IndexWriter is first created.

### getIndexCommit

    public IndexCommit getIndexCommit()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the `IndexCommit` as specified in `setIndexCommit(IndexCommit)` or the default, `null` which specifies to open the latest index commit point.

  Overrides:
    `getIndexCommit` in class `LiveIndexWriterConfig`

### setSimilarity

    public IndexWriterConfig setSimilarity(Similarity similarity)

  Expert: set the `Similarity` implementation used by this IndexWriter.

  NOTE: the similarity cannot be null.

  Only takes effect when IndexWriter is first created.

### getSimilarity

    public Similarity getSimilarity()

  Description copied from class: `LiveIndexWriterConfig`
  Expert: returns the `Similarity` implementation used by this `IndexWriter`.

  Overrides:
    `getSimilarity` in class `LiveIndexWriterConfig`

### setMergeScheduler

    public IndexWriterConfig setMergeScheduler(MergeScheduler mergeScheduler)

  Expert: sets the merge scheduler used by this writer. The default is `ConcurrentMergeScheduler`.

  NOTE: the merge scheduler cannot be null.

  Only takes effect when IndexWriter is first created.

### getMergeScheduler

    public MergeScheduler getMergeScheduler()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the `MergeScheduler` that was set by `setMergeScheduler(MergeScheduler)`.

  Overrides:
    `getMergeScheduler` in class `LiveIndexWriterConfig`

### setWriteLockTimeout

    public IndexWriterConfig setWriteLockTimeout(long writeLockTimeout)

  Sets the maximum time to wait for a write lock (in milliseconds) for this instance. You can change the default value for all instances by calling `setDefaultWriteLockTimeout(long)`.

  Only takes effect when IndexWriter is first created.

### getWriteLockTimeout

    public long getWriteLockTimeout()

  Description copied from class: `LiveIndexWriterConfig`
  Returns allowed timeout when acquiring the write lock.

  Overrides:
    `getWriteLockTimeout` in class `LiveIndexWriterConfig`
  See Also:
    `setWriteLockTimeout(long)`

### setMergePolicy

    public IndexWriterConfig setMergePolicy(MergePolicy mergePolicy)

  Expert: `MergePolicy` is invoked whenever there are changes to the segments in the index. Its role is to select which merges to do, if any, and return a `MergePolicy.MergeSpecification` describing the merges. It also selects merges to do for forceMerge.

  Only takes effect when IndexWriter is first created.

### setCodec

    public IndexWriterConfig setCodec(Codec codec)

  Set the `Codec`.

  Only takes effect when IndexWriter is first created.

### getCodec

    public Codec getCodec()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the current `Codec`.

  Overrides:
    `getCodec` in class `LiveIndexWriterConfig`

### getMergePolicy

    public MergePolicy getMergePolicy()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the current MergePolicy in use by this writer.

  Overrides:
    `getMergePolicy` in class `LiveIndexWriterConfig`
  See Also:
    `setMergePolicy(MergePolicy)`

### setMaxThreadStates

    public IndexWriterConfig setMaxThreadStates(int maxThreadStates)

  Sets the max number of simultaneous threads that may be indexing documents at once in IndexWriter. Values < 1 are invalid and if passed `maxThreadStates` will be set to `DEFAULT_MAX_THREAD_STATES`.

  Only takes effect when IndexWriter is first created.

### getMaxThreadStates

    public int getMaxThreadStates()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the max number of simultaneous threads that may be indexing documents at once in IndexWriter.

  Overrides:
    `getMaxThreadStates` in class `LiveIndexWriterConfig`

### setReaderPooling

    public IndexWriterConfig setReaderPooling(boolean readerPooling)

  By default, IndexWriter does not pool the SegmentReaders it must open for deletions and merging, unless a near-real-time reader has been obtained by calling `DirectoryReader.open(IndexWriter, boolean)`. This method lets you enable pooling without getting a near-real-time reader. NOTE: if you set this to false, IndexWriter will still pool readers once `DirectoryReader.open(IndexWriter, boolean)` is called.

  Only takes effect when IndexWriter is first created.

### getReaderPooling

    public boolean getReaderPooling()

  Description copied from class: `LiveIndexWriterConfig`
  Returns `true` if `IndexWriter` should pool readers even if `DirectoryReader.open(IndexWriter, boolean)` has not been called.

  Overrides:
    `getReaderPooling` in class `LiveIndexWriterConfig`

### setRAMPerThreadHardLimitMB

    public IndexWriterConfig setRAMPerThreadHardLimitMB(int perThreadHardLimitMB)

  Expert: Sets the maximum memory consumption per thread triggering a forced flush if exceeded. A `DocumentsWriterPerThread` is forcefully flushed once it exceeds this limit even if the `getRAMBufferSizeMB()` has not been exceeded. This is a safety limit to prevent a `DocumentsWriterPerThread` from address space exhaustion due to its internal 32 bit signed integer based memory addressing. The given value must be less that 2GB (2048MB)

  See Also:
    `DEFAULT_RAM_PER_THREAD_HARD_LIMIT_MB`

### getRAMPerThreadHardLimitMB

    public int getRAMPerThreadHardLimitMB()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the max amount of memory each `DocumentsWriterPerThread` can consume until forcefully flushed.

  Overrides:
    `getRAMPerThreadHardLimitMB` in class `LiveIndexWriterConfig`
  See Also:
    `setRAMPerThreadHardLimitMB(int)`

### getInfoStream

    public InfoStream getInfoStream()

  Description copied from class: `LiveIndexWriterConfig`
  Returns `InfoStream` used for debugging.

  Overrides:
    `getInfoStream` in class `LiveIndexWriterConfig`
  See Also:
    `setInfoStream(InfoStream)`

### getAnalyzer

    public Analyzer getAnalyzer()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the default analyzer to use for indexing documents.

  Overrides:
    `getAnalyzer` in class `LiveIndexWriterConfig`

### getMaxBufferedDeleteTerms

    public int getMaxBufferedDeleteTerms()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the number of buffered deleted terms that will trigger a flush of all buffered deletes if enabled.

  Overrides:
    `getMaxBufferedDeleteTerms` in class `LiveIndexWriterConfig`
  See Also:
    `LiveIndexWriterConfig.setMaxBufferedDeleteTerms(int)`

### getMaxBufferedDocs

    public int getMaxBufferedDocs()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the number of buffered added documents that will trigger a flush if enabled.

  Overrides:
    `getMaxBufferedDocs` in class `LiveIndexWriterConfig`
  See Also:
    `LiveIndexWriterConfig.setMaxBufferedDocs(int)`

### getMergedSegmentWarmer

    public IndexWriter.IndexReaderWarmer getMergedSegmentWarmer()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the current merged segment warmer. See `IndexWriter.IndexReaderWarmer`.

  Overrides:
    `getMergedSegmentWarmer` in class `LiveIndexWriterConfig`

### getRAMBufferSizeMB

    public double getRAMBufferSizeMB()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the value set by `LiveIndexWriterConfig.setRAMBufferSizeMB(double)` if enabled.

  Overrides:
    `getRAMBufferSizeMB` in class `LiveIndexWriterConfig`

### getReaderTermsIndexDivisor

    public int getReaderTermsIndexDivisor()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the `termInfosIndexDivisor`.

  Overrides:
    `getReaderTermsIndexDivisor` in class `LiveIndexWriterConfig`
  See Also:
    `LiveIndexWriterConfig.setReaderTermsIndexDivisor(int)`

### getTermIndexInterval

    public int getTermIndexInterval()

  Description copied from class: `LiveIndexWriterConfig`
  Returns the interval between indexed terms.

  Overrides:
    `getTermIndexInterval` in class `LiveIndexWriterConfig`
  See Also:
    `LiveIndexWriterConfig.setTermIndexInterval(int)`

### setInfoStream

    public IndexWriterConfig setInfoStream(InfoStream infoStream)

  If non-null, information about merges, deletes and a message when maxFieldLength is reached will be printed to this.

### setInfoStream

    public IndexWriterConfig setInfoStream(PrintStream printStream)

  Convenience method that uses `PrintStreamInfoStream`

### setMaxBufferedDeleteTerms

    public IndexWriterConfig setMaxBufferedDeleteTerms(int maxBufferedDeleteTerms)

  Description copied from class: `LiveIndexWriterConfig`
  Determines the minimal number of delete terms required before the buffered in-memory delete terms and queries are applied and flushed.

  Disabled by default (writer flushes by RAM usage).

  NOTE: This setting won't trigger a segment flush.

  Takes effect immediately, but only the next time a document is added, updated or deleted.

  Overrides:
    `setMaxBufferedDeleteTerms` in class `LiveIndexWriterConfig`
  See Also:
    `LiveIndexWriterConfig.setRAMBufferSizeMB(double)`

### setMaxBufferedDocs

    public IndexWriterConfig setMaxBufferedDocs(int maxBufferedDocs)

  Description copied from class: `LiveIndexWriterConfig`
  Determines the minimal number of documents required before the buffered in-memory documents are flushed as a new Segment. Large values generally give faster indexing.

  When this is set, the writer will flush every maxBufferedDocs added documents. Pass in `DISABLE_AUTO_FLUSH` to prevent triggering a flush due to number of buffered documents. Note that if flushing by RAM usage is also enabled, then the flush will be triggered by whichever comes first.

  Disabled by default (writer flushes by RAM usage).

  Takes effect immediately, but only the next time a document is added, updated or deleted.

  Overrides:
    `setMaxBufferedDocs` in class `LiveIndexWriterConfig`
  See Also:
    `LiveIndexWriterConfig.setRAMBufferSizeMB(double)`

### setMergedSegmentWarmer

    public IndexWriterConfig setMergedSegmentWarmer(IndexWriter.IndexReaderWarmer mergeSegmentWarmer)

  Description copied from class: `LiveIndexWriterConfig`
  Set the merged segment warmer. See `IndexWriter.IndexReaderWarmer`.

  Takes effect on the next merge.

  Overrides:
    `setMergedSegmentWarmer` in class `LiveIndexWriterConfig`

### setRAMBufferSizeMB

    public IndexWriterConfig setRAMBufferSizeMB(double ramBufferSizeMB)

  Description copied from class: `LiveIndexWriterConfig`
  Determines the amount of RAM that may be used for buffering added documents and deletions before they are flushed to the Directory. Generally for faster indexing performance it's best to flush by RAM usage instead of document count and use as large a RAM buffer as you can.

  When this is set, the writer will flush whenever buffered documents and deletions use this much RAM. Pass in `DISABLE_AUTO_FLUSH` to prevent triggering a flush due to RAM usage. Note that if flushing by document count is also enabled, then the flush will be triggered by whichever comes first.

  The maximum RAM limit is inherently determined by the JVMs available memory. Yet, an `IndexWriter` session can consume a significantly larger amount of memory than the given RAM limit since this limit is just an indicator when to flush memory resident documents to the Directory. Flushes are likely happen concurrently while other threads adding documents to the writer. For application stability the available memory in the JVM should be significantly larger than the RAM buffer used for indexing.

  NOTE: the account of RAM usage for pending deletions is only approximate. Specifically, if you delete by Query, Lucene currently has no way to measure the RAM usage of individual Queries so the accounting will under-estimate and you should compensate by either calling commit() periodically yourself, or by using `LiveIndexWriterConfig.setMaxBufferedDeleteTerms(int)` to flush and apply buffered deletes by count instead of RAM usage (for each buffered delete Query a constant number of bytes is used to estimate RAM usage). Note that enabling `LiveIndexWriterConfig.setMaxBufferedDeleteTerms(int)` will not trigger any segment flushes.

  NOTE: It's not guaranteed that all memory resident documents are flushed once this limit is exceeded. Depending on the configured `FlushPolicy` only a subset of the buffered documents are flushed and therefore only parts of the RAM buffer is released.

  The default value is `DEFAULT_RAM_BUFFER_SIZE_MB`.

  Takes effect immediately, but only the next time a document is added, updated or deleted.

  Overrides:
    `setRAMBufferSizeMB` in class `LiveIndexWriterConfig`
  See Also:
    `setRAMPerThreadHardLimitMB(int)`

### setReaderTermsIndexDivisor

    public IndexWriterConfig setReaderTermsIndexDivisor(int divisor)

  Description copied from class: `LiveIndexWriterConfig`
  Sets the termsIndexDivisor passed to any readers that IndexWriter opens, for example when applying deletes or creating a near-real-time reader in `DirectoryReader.open(IndexWriter, boolean)`. If you pass -1, the terms index won't be loaded by the readers. This is only useful in advanced situations when you will only .next() through all terms; attempts to seek will hit an exception.

  Takes effect immediately, but only applies to readers opened after this call

  NOTE: divisor settings > 1 do not apply to all PostingsFormat implementations, including the default one in this release. It only makes sense for terms indexes that can efficiently re-sample terms at load time.

  Overrides:
    `setReaderTermsIndexDivisor` in class `LiveIndexWriterConfig`

### setTermIndexInterval

    public IndexWriterConfig setTermIndexInterval(int interval)

  Description copied from class: `LiveIndexWriterConfig`
  Expert: set the interval between indexed terms. Large values cause less memory to be used by IndexReader, but slow random-access to terms. Small values cause more memory to be used by an IndexReader, and speed random-access to terms.

  This parameter determines the amount of computation required per query term, regardless of the number of documents that contain that term. In particular, it is the maximum number of other terms that must be scanned before a term is located and its frequency and position information may be processed. In a large index with user-entered query terms, query processing time is likely to be dominated not by term lookup but rather by the processing of frequency and positional data. In a small index or when many uncommon query terms are generated (e.g., by wildcard queries) term lookup may become a dominant cost.

  In particular, `numUniqueTerms/interval` terms are read into memory by an IndexReader, and, on average, `interval/2` terms must be scanned for each random term access.

  Takes effect immediately, but only applies to newly flushed/merged segments.

  NOTE: This parameter does not apply to all PostingsFormat implementations, including the default one in this release. It only makes sense for term indexes that are implemented as a fixed gap between terms. For example, `Lucene41PostingsFormat` implements the term index instead based upon how terms share prefixes. To configure its parameters (the minimum and maximum size for a block), you would instead use `Lucene41PostingsFormat.Lucene41PostingsFormat(int, int)`. which can also be configured on a per-field basis:

       //customize Lucene41PostingsFormat, passing minBlockSize=50, maxBlockSize=100
       final PostingsFormat tweakedPostings = new Lucene41PostingsFormat(50, 100);
       iwc.setCodec(new Lucene42Codec() {
         @Override
         public PostingsFormat getPostingsFormatForField(String field) {
           if (field.equals("fieldWithTonsOfTerms"))
             return tweakedPostings;
           else
             return super.getPostingsFormatForField(field);
         }
       });

  Note that other implementations may have their own parameters, or no parameters at all.

  Overrides:
    `setTermIndexInterval` in class `LiveIndexWriterConfig`
  See Also:
    `DEFAULT_TERM_INDEX_INTERVAL`

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