Dialect Support Matrix

SignalPilot supports 7 SQL dialects across three tiers.

Tier overview

Tier	Connectors	Query	Schema	Cost estimate	EXPLAIN	FK discovery	Schema stats
1	PostgreSQL, DuckDB, Snowflake, BigQuery	Full	Full	Yes	Yes	Yes	Yes
2	MySQL, SQLite, SQL Server	Full	Full	Limited	Yes	Yes	Partial
3	Databricks	Full	Partial	No	Basic	Limited	No

Per-dialect details

PostgreSQL (Tier 1)

• Full schema introspection via information_schema and pg_catalog
• FK discovery via pg_constraint
• EXPLAIN (ANALYZE, BUFFERS) for execution plans
• No cost estimation (row-based billing, not byte-based)
• Dangerous functions blocked: pg_read_file, pg_read_binary_file, pg_ls_dir, lo_import, lo_export, dblink
• Plugin skill: use sql-workflow for query patterns

DuckDB (Tier 1)

• Full schema introspection via information_schema
• FK discovery supported
• EXPLAIN supported
• No cost estimation
• Dangerous functions blocked: read_csv, read_parquet, read_json, httpfs extensions
• Gotchas: integer division truncates, INTERVAL syntax requires quotes, DATE_TRUNC returns TIMESTAMP
• Plugin skill: duckdb-sql — covers all major DuckDB-specific patterns

Snowflake (Tier 1)

• Full schema introspection via INFORMATION_SCHEMA
• FK discovery via SHOW PRIMARY KEYS / SHOW IMPORTED KEYS
• EXPLAIN supported (estimated cost, not actual)
• Cost estimation: estimated credits based on bytes scanned
• No dangerous functions blocked (Snowflake's sandbox model handles this)
• LIMIT injection uses LIMIT n syntax
• Plugin skill: snowflake-sql — QUALIFY, LATERAL FLATTEN, VARIANT

BigQuery (Tier 1)

• Full schema introspection via INFORMATION_SCHEMA
• FK discovery limited (BigQuery doesn't enforce FKs at write time)
• Cost estimation: exact bytes billed via dry-run (estimate_query_cost is highly accurate)
• EXPLAIN returns query plan with byte estimates per stage
• Table references require backtick quoting: `project.dataset.table`
• Plugin skill: bigquery-sql — UNNEST, STRUCT, EXCEPT/REPLACE, partitioned tables

MySQL (Tier 2)

• Schema introspection via information_schema
• FK discovery via KEY_COLUMN_USAGE
• EXPLAIN supported
• No byte-based cost estimation
• Dangerous functions blocked: LOAD_FILE, INTO OUTFILE, INTO DUMPFILE, LOAD DATA INFILE
• No FULL OUTER JOIN (use UNION of LEFT and RIGHT)
• Plugin skill: use sql-workflow for general patterns

SQLite (Tier 2)

• Schema introspection via sqlite_master
• FK discovery via PRAGMA foreign_key_list
• No cost estimation
• No FULL OUTER JOIN
• No ILIKE (use LIKE with LOWER())
• No SPLIT_PART or POSITION (use substr/instr)
• String concatenation: || operator
• Plugin skill: sqlite-sql — covers all major SQLite-specific patterns

SQL Server / MSSQL (Tier 2)

• Schema introspection via INFORMATION_SCHEMA and sys catalog
• FK discovery via sys.foreign_keys
• EXPLAIN via SET STATISTICS IO ON
• No byte-based cost estimation
• Dangerous functions blocked: xp_cmdshell, xp_fileexist, xp_readfile, sp_OACreate, OPENROWSET, BULK INSERT
• LIMIT injection uses SELECT TOP n (not LIMIT n)
• Plugin skill: use sql-workflow for general patterns

Databricks (Tier 3)

• Schema introspection via information_schema
• Limited FK discovery (Delta tables don't enforce FKs)
• Basic EXPLAIN support
• No cost estimation
• Plugin skill: use sql-workflow for general patterns

Dialect detection

SignalPilot detects the dialect from the connection's db_type field. You can check the detected dialect and feature tier with connector_capabilities.

Cross-dialect skill mapping

Dialect	Recommended skill
DuckDB	duckdb-sql
Snowflake	snowflake-sql
BigQuery	bigquery-sql
SQLite	sqlite-sql
PostgreSQL, MySQL, SQL Server, Databricks	sql-workflow