@Rocky can you tell me why starrocks VARCHAR type only support 1MB maximum?

Hello! I'm Rocky. That's a great question about StarRocks' technical design. The 1MB (specifically 1,048,576 bytes) limit for the

VARCHAR

type in StarRocks (starting from version 2.1) exists primarily due to internal storage architecture and memory management efficiency. Here are the key reasons why this limit is in place: 1. Maximum Row Size Constraint In StarRocks' internal storage format, there is a limit on the maximum size of a single row, which is approximately 1,048,578 bytes. * A

VARCHAR

value uses a 2-byte length prefix to store the actual size of the string. * $1,048,578 \text{ (Max Row)} - 2 \text{ (Prefix)} = 1,048,576 \text{ bytes (1MB)}$. Because of this row-level limit, a single

VARCHAR

field cannot exceed this capacity. 2. Memory Pre-allocation and Query Performance StarRocks is a high-performance OLAP engine that uses vectorized execution. To achieve extreme speed, the execution engine often pre-allocates memory blocks during query processing. * In many query scenarios, memory is allocated based on the defined length of the

VARCHAR

column rather than the actual data length of each row. * If

VARCHAR

were allowed to be massive (e.g., several hundred MBs), a query involving multiple such columns could easily cause an Out of Memory (OOM) error, as the system would attempt to reserve huge chunks of memory for data that might not even be there. 3. OLAP Optimization StarRocks is optimized for analytical workloads (aggregations, joins, etc.) rather than serving as a BLOB or document store. Columnar storage and vectorized processing work best when data fits within certain bounds. Extremely large text fields can degrade performance by: * Increasing I/O overhead. * Reducing the efficiency of the CPU cache. * Making the "short-key index" less effective if large strings are placed early in the schema. Important Notes: * Before Version 2.1: The limit was even smaller—only 65,533 bytes (approx. 64KB). * Best Practice: Always set your

VARCHAR

length to the smallest necessary value. For example, if an

address

field only needs 200 bytes, use

VARCHAR(200)

instead of the maximum. This helps the query optimizer manage memory more efficiently. * STRING Type: In StarRocks, the

STRING

type is essentially an alias for

VARCHAR

with a large default length, but it is still subject to these same underlying architectural limits. If you have data larger than 1MB, it is usually recommended to store the large content in an external object store (like S3) and keep the URI/link in StarRocks, or split the data if appropriate for your analysis. References • faq/table_design_faq.md • knowledge/usage/best-practice.md • sql-reference/System_limit.md • faq/Others.md • sql-reference/data-types/string-type/BINARY.md