Summary

Adds Doris SQL dialect support to close #2379

This is PR 2 of a stacked Doris SQL support series. previous PR: #2380

This PR introduces DorisDialect and parser/AST support for common Doris SQL syntax, especially Doris CREATE TABLE clauses, partition/distribution definitions, table properties, Doris column options, and Doris load statements.

Changes

• Add DorisDialect

  • backtick-delimited identifiers
  • Doris-style identifiers
  • backslash string escapes
  • Doris-specific parser capability gates

• Add Doris CREATE TABLE support

  • ENGINE = OLAP
  • DUPLICATE KEY, UNIQUE KEY, AGGREGATE KEY
  • table-level COMMENT
  • PARTITION BY RANGE/LIST
  • AUTO PARTITION
  • partition values including MAXVALUE / MAX_VALUE
  • fixed and batch range partitions
  • DISTRIBUTED BY HASH/RANDOM
  • BUCKETS <n> and BUCKETS AUTO
  • PROPERTIES (...)

• Add Doris AST structures

  • key model
  • partition model
  • distribution model
  • bucket declarations
  • Doris load statements

• Add Doris-specific statement parsing

  • LOAD DATA INFILE
  • CREATE ROUTINE LOAD

• Extend tests

  • Doris round-trip parser tests
  • structured AST assertions
  • generic/ANSI rejection cases for Doris-only syntax
  • table comment escaping
  • compatibility checks for surrounding dialect behavior

Testing

cargo fmt --check
cargo test --test sqlparser_doris