Function pg_chr_decompose 

pub fn pg_chr_decompose(payload: &str) -> String

Postgres / Oracle CHR()-function decomposition — CHR(N) || CHR(N) || ... per char of every single-quoted string literal.

Input 'admin' → output (CHR(97)||CHR(100)||CHR(109)||CHR(105)||CHR(110))

Differs from sql_char_decompose (which uses MySQL’s variadic CHAR(N1,N2,...)) — Postgres / Oracle CHR() is unary, so codepoints are concatenated via the SQL standard || pipe operator. The wrapping parens preserve precedence inside larger expressions (WHERE u = ...).

Postgres-specific: codepoints up to U+10FFFF are valid; Oracle CHR(N) treats N modulo NLS_CHARACTERSET size (often 256-modular for WE8MSWIN1252). For ASCII payloads (the common case) both behave identically.

Empty literal → (''). Unbalanced quote → passed through.