datus-ai/datus-db-adapters/db-hologres-sql

Hologres SQL

Generate Hologres-compatible SQL from metadata-provided object and column names. Treat PostgreSQL 11 as the baseline syntax, but use only the subset and extensions that Hologres supports.

Namespaces and identifiers

• Address ordinary objects in the connected database as schema.table; use public only when metadata or connection context selects it.
• Treat the connection database as context, not as an automatic SQL qualifier. Use external_database.schema.table only when metadata identifies a Hologres V3.0+ external database.
• Use configured foreign tables for other Hologres databases or external systems instead of assuming generic PostgreSQL cross-database qualification.
• Fold unquoted identifiers to lowercase. Preserve mixed case, reserved words, and special characters with double quotes; do not use backticks or square brackets.
• Avoid names reserved by Hologres, including column names beginning with hg_ and schema names beginning with holo_, hg_, or pg_.

Queries and types

• Use PostgreSQL-style LIMIT and OFFSET, casts, joins, window functions, and expressions only where supported by the target Hologres version.
• Prefer TEXT for an unbounded string and VARCHAR(n) only when a length bound is meaningful.
• Use Hologres-supported PostgreSQL types such as SMALLINT, INTEGER, BIGINT, NUMERIC, REAL, DOUBLE PRECISION, BOOLEAN, TEXT, BYTEA, DATE, TIMESTAMP, and TIMESTAMPTZ according to metadata.
• Confirm version support before generating newer Hologres types, functions, logical partitions, dynamic tables, or external databases.

Avoid common dialect leaks

Before returning SQL, reject MySQL backticks, MySQL table options, Snowflake three-part names, unsupported PostgreSQL constraints, unconditional cross-database qualification, and Hologres properties placed outside their supported creation syntax.

Read existing table semantics

• Use declared primary-key metadata; orientation, distribution_key, clustering_key and event_time_column describe storage or pruning and do not by themselves establish uniqueness.
• Foreign tables map to MaxCompute, OSS/DLF or another Hologres source. Resolve their actual server and source context when interpreting SQL rather than treating them as locally stored internal tables.

Task references

• Hologres table design and writes: internal and foreign-table creation, storage properties, writes and transactions.

Read these for the requested operation, including SQL-only authoring. Supplied ETL is evidence; follow the user's task.