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Database / LanceDB Interview questions

Define a table in LanceDB?

A table in LanceDB is the core unit of data storage — a columnar collection of rows sharing a defined schema, conceptually similar to a table in a relational database, except its columns commonly include a fixed-size vector column alongside ordinary scalar columns like strings or numbers.

import lancedb

db = lancedb.connect("./my_lancedb")
table = db.create_table(
    "documents",
    data=[{"text": "hello world", "vector": [0.1, 0.2, 0.3]}]
)

Each table is backed by one or more Lance-format data files on disk (or in object storage), and every write to a table — adding rows, updating them, deleting them, or changing the schema — creates a new version of that table rather than mutating existing data files in place.

Tables support both a strongly-typed schema (defined via Arrow types or a Pydantic model in Python) and flexible ingestion from common formats like a list of dictionaries or a Pandas DataFrame, so the schema can be inferred automatically from the first batch of data if one isn't explicitly declared upfront.

What commonly appears alongside ordinary scalar columns in a LanceDB table?
What happens to existing data files when a write is made to a table?

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What is LanceDB? What is the purpose of LanceDB? What is the Lance columnar format? What are the key features of LanceDB? What is an embedded vector database? What is Apache Arrow, and how does LanceDB use it? Define a table in LanceDB? What is a vector embedding? What are the supported languages/SDKs for LanceDB? How do you create a table in LanceDB? What is ANN (Approximate Nearest Neighbor) search? What is the IVF_PQ index in LanceDB? What is full-text search in LanceDB? What is hybrid search in LanceDB? Define the embedding function registry in LanceDB? What is schema evolution in LanceDB? List the storage backends supported by LanceDB? What is a scalar index in LanceDB? What is versioning in LanceDB? How do you connect to a LanceDB database? What is the difference between LanceDB and Pinecone? What is the difference between LanceDB and Chroma? What is the difference between LanceDB OSS and LanceDB Cloud? Why is LanceDB well suited for multimodal AI data? How does the Lance format differ from Parquet? Explain how IVF_PQ indexing works internally? What is the difference between IVF_PQ and HNSW indexing in LanceDB? How does LanceDB implement hybrid search using reranking? What is Reciprocal Rank Fusion (RRF), and how is it used in LanceDB? Explain the lifecycle of a write operation in LanceDB (versioning)? How do you perform time travel queries in LanceDB? What is the difference between checkout and restore in LanceDB? What are tags in LanceDB versioning? What are branches in LanceDB, and how do they differ from tags? How does LanceDB handle deletes internally? Explain the internal working of LanceDB's zero-copy data access via Arrow? How do you integrate LanceDB with LangChain for RAG? What is the role of DataFusion in LanceDB's query execution? How do you implement custom embedding functions in LanceDB? When should you use a scalar index versus a vector index? How do you optimize a LanceDB table for query performance through compaction? What is prefiltering vs postfiltering in LanceDB queries? Explain the internal working of product quantization (PQ) in vector indexing? How does LanceDB support multi-process concurrent access? What are the trade-offs of running LanceDB embedded versus as a managed cloud service? Explain the internal working of the manifest and commit protocol in Lance? How do you implement multimodal search across text and images in LanceDB? What is the role of object storage (S3/GCS) in LanceDB's architecture? How do you monitor and troubleshoot slow vector search queries in LanceDB? Explain the execution flow of a RAG pipeline built with LanceDB as the retrieval layer?
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