PostgreSQL Keyword Compatibility Reference

Generated for GSP Java version 4.1.9 on 2026-07-29

This page was generated using hybrid static extraction from parser source files combined with runtime validation against the actual GSP parser. Re-run the extraction script after parser updates to keep this page current.

Keyword-as-Column-Name Support

As of version 4.1.0.8, the GSP PostgreSQL parser includes a lexer lookahead mechanism that allows 36 vendor-unreserved keywords to be used as unquoted column names in SELECT statements.

The lookahead pre-scans the token list before parsing and converts context-specific keywords to identifiers when they appear in column-name position:

• After: SELECT, ,, DISTINCT, or ALL
• Before: FROM, AS, WHERE, GROUP, ORDER, HAVING, LIMIT, UNION, INTERSECT, EXCEPT, INTO, ,, ), or ;

-- Works: keyword as column name
SELECT array FROM t;

-- Works: keyword as column name
SELECT authorization FROM t;

-- Works: keyword as column name
SELECT binary FROM t;

-- Original keyword syntax also still works

---

Full Classification Overview

Out of 613 keywords recognized by the GSP PostgreSQL parser:

Classification	Count	Description
Allowed	582	Can be used as an unquoted column name in both canonical contexts
Context-specific	30	Fails as SELECT keyword FROM t but works as SELECT t.keyword FROM t
Blocked	1	Cannot be used as an unquoted column name in either context

Context-Specific Keywords (30)

These keywords parse in one canonical context but not the other (measured against the release stamped above).

Keyword	SELECT kw FROM t	SELECT t.kw FROM t
ALL	no	yes
BIGINT	no	yes
BOOLEAN	no	yes
DISTINCT	no	yes
DOUBLE	no	yes
FLOAT4	no	yes
FLOAT8	no	yes
GREATEST	no	yes
INT2	no	yes
INT4	no	yes
INT8	no	yes
LEAST	no	yes
NATIONAL	no	yes
NCHAR	no	yes
NULLIF	no	yes
NUMERIC	no	yes
OVERLAY	no	yes
REAL	no	yes
SMALLINT	no	yes
SUBSTRING	no	yes
TREAT	no	yes
VARCHAR	no	yes
XMLCONCAT	no	yes
XMLELEMENT	no	yes
XMLEXISTS	no	yes
XMLFOREST	no	yes
XMLPARSE	no	yes
XMLPI	no	yes
XMLROOT	no	yes
XMLSERIALIZE	no	yes

Blocked Keywords (1)

These keywords fail as unquoted identifiers in both canonical contexts. Workaround: quote the identifier (e.g. "KEYWORD").

Keyword
FROM

Workaround: Double-Quoted Identifiers

For any keyword that fails as an unquoted column name, you can use double-quoted identifiers:

-- Blocked or context-specific keyword as column name
SELECT "from" FROM t;

-- Or use table qualification for context-specific keywords
SELECT t.all FROM t;

Scope and Limitations

• Tested contexts: SELECT keyword FROM t and SELECT t.keyword FROM t. Other contexts (DDL column definitions, INSERT column lists, aliases) may behave differently.
• Version-specific: This report reflects GSP Java version 4.1.0.8.
• Case sensitivity: Keywords are case-insensitive. select, SELECT, and Select are all treated the same.

How to Report Discrepancies

If you encounter a keyword that behaves differently from what this page describes, please report it through your support channel. Include:

1. The exact SQL statement
2. The GSP parser version
3. Whether the same SQL works in PostgreSQL

Methodology

1. Static extraction: A Python script parses the lexer (.cod) and grammar (.y) source files to identify all 613 keywords and their grammar classifications.
2. Runtime validation: A Java test harness validates every classification against actual TGSqlParser runtime behavior.
3. JSON dataset: The authoritative data is stored in docs/generated/postgresql_keyword_compatibility.json.