-- Error handling of fbsql.fit_glm(). Every failure must surface a clear,
-- 'fit_glm:'-prefixed message (PL/R wraps it in DETAIL).
CREATE TEMP TABLE t_err (
    y double precision,
    x double precision
);
INSERT INTO t_err VALUES (1.0, 0.1), (2.0, 0.9), (3.1, 2.1), (3.9, 3.0);
-- Unsupported family.
SELECT * FROM fbsql.fit_glm(
    relation => $$ SELECT y, x FROM t_err $$,
    formula  => 'y ~ x',
    family   => 'poisson');
ERROR:  R interpreter expression evaluation error
DETAIL:  Error: fit_glm: family 'poisson' is not supported yet (supported families: gaussian, binomial)
CONTEXT:  In PL/R function fit_glm
-- Formula string that does not parse as an R formula.
SELECT * FROM fbsql.fit_glm(
    relation => $$ SELECT y, x FROM t_err $$,
    formula  => 'not a formula');
ERROR:  R interpreter expression evaluation error
DETAIL:  Error: fit_glm: invalid formula: 'not a formula'
CONTEXT:  In PL/R function fit_glm
-- Formula referencing a column the relation does not provide.
SELECT * FROM fbsql.fit_glm(
    relation => $$ SELECT y, x FROM t_err $$,
    formula  => 'y ~ missing_col');
ERROR:  R interpreter expression evaluation error
DETAIL:  Error: fit_glm: formula references column(s) not in relation: missing_col (available: y, x)
CONTEXT:  In PL/R function fit_glm
-- Broken relation SQL.
SELECT * FROM fbsql.fit_glm(
    relation => $$ SELECT * FROM no_such_table $$,
    formula  => 'y ~ x');
ERROR:  R interpreter expression evaluation error
DETAIL:  Error in pg.spi.exec(relation) : 
  error in SQL statement : relation "no_such_table" does not exist
CONTEXT:  In R support function pg.spi.exec
In PL/R function fit_glm
-- Relation that yields zero rows.
SELECT * FROM fbsql.fit_glm(
    relation => $$ SELECT y, x FROM t_err WHERE false $$,
    formula  => 'y ~ x');
ERROR:  R interpreter expression evaluation error
DETAIL:  Error: fit_glm: relation returned no rows
CONTEXT:  In PL/R function fit_glm
-- R-level fitting error (binomial response outside [0, 1]) keeps R's
-- informative message, prefixed with the function name.
SELECT * FROM fbsql.fit_glm(
    relation => $$ SELECT y, x FROM t_err $$,
    formula  => 'y ~ x',
    family   => 'binomial');
ERROR:  R interpreter expression evaluation error
DETAIL:  Error: fit_glm: y values must be 0 <= y <= 1
CONTEXT:  In PL/R function fit_glm