Skip to content

Commit b9ff26d

Browse files
solidsnacksolidsnack
committed
Greatly expand introspection.
Still haven't figured out JOINs yet.
1 parent 976e4f2 commit b9ff26d

File tree

1 file changed

+145
-28
lines changed

1 file changed

+145
-28
lines changed

‎graphql.sql

Lines changed: 145 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,6 @@
1+
BEGIN;
2+
3+
DROP SCHEMA IF EXISTS graphql CASCADE;
14
CREATE SCHEMA graphql;
25

36
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
@@ -51,26 +54,36 @@ type.
5154
5255
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
5356

54-
CREATE FUNCTION graphql.to_sql(expr text)
57+
SET LOCAL search_path TO graphql; -- Definitions will be created in this schema
58+
--- However, we must still qualify references between functions -- as when
59+
--- to_sql calls parse_many -- because the search_path will be different when
60+
--- the code is run by the application/user.
61+
62+
CREATE FUNCTION to_sql(expr text)
5563
RETURNS TABLE (query text) AS $$
5664
BEGIN
5765
RETURN QUERY SELECT graphql.to_sql(selector, predicate, body)
5866
FROM graphql.parse_many(expr);
5967
END
6068
$$ LANGUAGE plpgsql STABLE STRICT;
6169

62-
CREATE FUNCTION graphql.to_sql(selector text, predicate text, body text)
70+
CREATE FUNCTION to_sql(selector text, predicate text, body text)
6371
RETURNS text AS $$
6472
DECLARE
6573
q text;
6674
tab regclass = selector::regclass; -- Without a parent, we need a table
6775
cols text[];
76+
col text;
6877
sub record;
69-
pk text;
78+
pk text = NULL;
79+
fk record;
80+
subselects text[];
7081
BEGIN
7182
q := 'FROM ' || tab; -- Regclass is auto-escaped
7283
body := substr(body, 2, length(body)-2);
7384
IF predicate IS NOT NULL THEN
85+
SELECT array_to_string(array_agg(format('%I', col)), ', ')
86+
FROM unnest(graphql.pk(tab)) INTO pk;
7487
SELECT array_to_string(array_agg(format('%I', col)), ', ')
7588
FROM graphql.pk(tab) INTO pk;
7689
q := q || E'\n WHERE (' || pk || ') = (' || predicate || ')';
@@ -81,20 +94,74 @@ BEGIN
8194
RAISE EXCEPTION 'Unhandled nested selector %(%)',
8295
sub.selector, sub.predicate;
8396
END IF;
84-
--- TODO: Handle nested lookup into JSON, HStore, RECORD
85-
--- TODO: Introduce foreign key magicks
86-
cols := cols || format('%I', sub.selector);
97+
SELECT col FROM cols(tab) WHERE col = sub.selector INTO col;
98+
CASE
99+
WHEN FOUND AND sub.body IS NULL THEN -- A simple column reference
100+
SELECT * FROM graphql.fk(tab)
101+
WHERE cols[1] = col AND cardinality(cols) = 1
102+
INTO fk; -- TODO: If there's more than one, emit a clear message.
103+
IF FOUND THEN
104+
subselects := subselects
105+
|| format(E'SELECT to_json(%1$I) AS %4$I FROM %1$I\n'
106+
' WHERE %1$I.%2$I = %3$I.%4$I',
107+
fk.other, fk.refs[1], tab, col);
108+
cols := cols || format('%I.%I', 'sub/'||cardinality(subselects), col);
109+
ELSE
110+
cols := cols || format('%I', col);
111+
END IF;
112+
WHEN FOUND AND sub.body IS NOT NULL THEN -- Index into a column
113+
--- TODO: Handle nested lookup into JSON, HStore, RECORD
114+
--- TODO: If col REFERENCES something, push lookup down to it
115+
WHEN NOT FOUND THEN -- It might be a reference to another table
116+
SELECT fk.*
117+
FROM graphql.fk(sub.selector),
118+
LATERAL (SELECT num FROM graphql.cols(tab)
119+
WHERE col = fk.cols[1]) AS _
120+
WHERE cardinality(fk.cols) = 1 AND fk.tab = to_sql.tab
121+
ORDER BY _.num LIMIT 1 INTO fk;
122+
IF NOT FOUND THEN
123+
RAISE EXCEPTION 'Not able to construct a JOIN for missing column: %',
124+
sub.selector;
125+
END IF;
126+
--- If:
127+
--- * Thare are two and only two foreign keys for the other table, and
128+
--- * All the columns of the table participate in one or the other
129+
--- foreign key, then
130+
--- * We can treat the table as a JOIN table and follow the keys.
131+
--- Otherwise:
132+
--- * We use the existence of the foreign key to look up the record in
133+
--- the table that JOINs with us.
134+
--- Whenever we are looking at a table that REFERENCES us, we assume it
135+
--- is a many-to-one relationship; and expect to return an array-valued
136+
--- result.
137+
IF FALSE THEN
138+
--- Recursion happens in here
139+
ELSE
140+
--- Recursion happens in here
141+
END IF;
142+
ELSE
143+
RAISE EXCEPTION 'Not able to interpret this selector: %', sub.selector;
144+
END CASE;
87145
END LOOP;
88-
IF cols > ARRAY[]::text[] THEN
89-
q := 'SELECT ' || array_to_string(cols, ', ') || E' \n ' || q;
90-
ELSE
91-
q := 'SELECT *' || E' \n ' || q;
92-
END IF;
146+
DECLARE
147+
column_expression text;
148+
BEGIN
149+
IF cols > ARRAY[]::text[] THEN
150+
column_expression := array_to_string(cols, ', ');
151+
ELSE
152+
column_expression := format('%I', tab);
153+
END IF;
154+
IF pk IS NOT NULL THEN -- Implies single result
155+
q := 'SELECT to_json(' || column_expression || E')\n ' || q;
156+
ELSE
157+
q := 'SELECT json_agg(' || column_expression || E')\n ' || q;
158+
END IF;
159+
END;
93160
RETURN q;
94161
END
95162
$$ LANGUAGE plpgsql STABLE STRICT;
96163

97-
CREATE FUNCTION graphql.parse_many(expr text)
164+
CREATE FUNCTION parse_many(expr text)
98165
RETURNS TABLE (selector text, predicate text, body text) AS $$
99166
DECLARE
100167
whitespace text = E' \t\n';
@@ -118,11 +185,11 @@ BEGIN
118185
END
119186
$$ LANGUAGE plpgsql IMMUTABLE STRICT;
120187

121-
CREATE FUNCTION graphql.parse_one(expr text,
122-
OUT selector text,
123-
OUT predicate text,
124-
OUT body text,
125-
OUT remainder text) AS $$
188+
CREATE FUNCTION parse_one(expr text,
189+
OUT selector text,
190+
OUT predicate text,
191+
OUT body text,
192+
OUT remainder text) AS $$
126193
DECLARE
127194
label text = '[a-zA-Z_][a-zA-Z0-9_]*';
128195
selector_re text = '^(' || label || ')' || '([(]([^()]+)[)])?';
@@ -170,17 +237,67 @@ BEGIN
170237
END
171238
$$ LANGUAGE plpgsql IMMUTABLE STRICT;
172239

173-
CREATE FUNCTION graphql.pk(tab regclass)
174-
RETURNS TABLE (col name, typ regtype) AS $$
175-
SELECT attname, atttypid::regtype
176-
FROM pg_index JOIN pg_attribute ON (attnum = ANY (indkey))
177-
WHERE indrelid = tab AND indisprimary AND attrelid = tab AND attnum > 0
178-
ORDER BY attnum
179-
$$ LANGUAGE sql STABLE STRICT;
180-
--- NB: For SELECTs, it would be okay just to return the column numbers. One
181-
--- could skip the JOIN with pg_attribute, resulting in a faster query.
182-
183-
CREATE FUNCTION graphql.excerpt(str text, start integer, length integer)
240+
CREATE FUNCTION excerpt(str text, start integer, length integer)
184241
RETURNS text AS $$
185242
SELECT substr(regexp_replace(str, '[ \n\t]+', ' ', 'g'), start, length);
186243
$$ LANGUAGE sql IMMUTABLE STRICT;
244+
245+
246+
/* * * * * * * * * * * * * Table inspection functions * * * * * * * * * * * */
247+
248+
CREATE VIEW pk AS
249+
SELECT attrelid::regclass AS tab,
250+
array_agg(attname)::name[] AS cols
251+
FROM pg_attribute
252+
JOIN pg_index ON (attrelid = indrelid AND attnum = ANY (indkey))
253+
WHERE indisprimary
254+
GROUP BY attrelid;
255+
256+
CREATE VIEW cols AS
257+
SELECT attrelid::regclass AS tab,
258+
attname::name AS col,
259+
atttypid::regtype AS typ,
260+
attnum AS num
261+
FROM pg_attribute
262+
WHERE attnum > 0
263+
ORDER BY attrelid, attnum;
264+
265+
CREATE VIEW fk AS
266+
SELECT conrelid::regclass AS tab,
267+
names.cols,
268+
confrelid::regclass AS other,
269+
names.refs
270+
FROM pg_constraint,
271+
LATERAL (SELECT array_agg(cols.attname) AS cols,
272+
array_agg(refs.attname) AS refs
273+
FROM unnest(conkey, confkey) AS _(col, ref),
274+
LATERAL (SELECT * FROM pg_attribute
275+
WHERE attrelid = conrelid AND attnum = col)
276+
AS cols,
277+
LATERAL (SELECT * FROM pg_attribute
278+
WHERE attrelid = confrelid AND attnum = ref)
279+
AS refs)
280+
AS names
281+
WHERE confrelid != 0;
282+
283+
CREATE FUNCTION ns(tab regclass) RETURNS name AS $$
284+
SELECT nspname
285+
FROM pg_class JOIN pg_namespace ON (pg_namespace.oid = relnamespace)
286+
WHERE pg_class.oid = tab
287+
$$ LANGUAGE sql STABLE STRICT;
288+
289+
CREATE FUNCTION pk(t regclass) RETURNS name[] AS $$
290+
SELECT cols FROM meta.pk WHERE meta.pk.tab = t;
291+
$$ LANGUAGE sql STABLE STRICT;
292+
293+
CREATE FUNCTION cols(t regclass)
294+
RETURNS TABLE (num smallint, col name, typ regtype) AS $$
295+
SELECT num, col, typ FROM meta.cols WHERE meta.cols.tab = t;
296+
$$ LANGUAGE sql STABLE STRICT;
297+
298+
CREATE FUNCTION fk(t regclass)
299+
RETURNS TABLE (cols name[], other regclass, refs name[]) AS $$
300+
SELECT cols, other, refs FROM meta.fk WHERE meta.fk.tab = t;
301+
$$ LANGUAGE sql STABLE STRICT;
302+
303+
COMMIT;

0 commit comments

Comments
 (0)