Writer configuration

IndexWriterConfig exposes the knobs that affect buffering, merging, compression, and analysis.

Common settings

var config = new IndexWriterConfig
{
    DefaultAnalyser = new StandardAnalyser(),
    RamBufferSizeMB = 256.0,
    MaxBufferedDocs = 10_000,
    MaxQueuedDocs   = 20_000,
    MergeThreshold  = 10,
    DurableCommits  = true,
    CompressionPolicy = FieldCompressionPolicy.Lz4,
    StoredFieldBlockSize = 16,
};

Defaults

Setting	Default
RamBufferSizeMB	256.0
MaxBufferedDocs	10_000
MaxQueuedDocs	20_000
DefaultAnalyser	StandardAnalyser
Similarity	Bm25Similarity.Instance
DeletionPolicy	KeepLatestCommitPolicy
DurableCommits	true
CompressionPolicy	Lz4
StoredFieldBlockSize	16
PostingsSkipInterval	128
MergeThreshold	10
BKDMaxLeafSize	512
MaxTokensPerDocument	0 (unlimited)
TokenBudgetPolicy	Truncate
Metrics	NullMetricsCollector.Instance

What each knob affects

• RamBufferSizeMB / MaxBufferedDocs: in-memory buffer before a flush.
• MergeThreshold: number of segments before a background merge runs.
• DurableCommits: when true, fsyncs before declaring a commit successful.
• Schema: optional IndexSchema; rejects bad documents at AddDocument time.

See also

• IndexWriterConfig
• FieldCompressionPolicy