workload: remove FK dependency check in schemachanger drop column

The schemachanger previously attempted to predict whether a DROP COLUMN
operation would fail due to a foreign key (FK) dependency. This logic has
proven to be unreliable and difficult to maintain correctly.

Rather than investing more effort into fixing the latest edge cases, we’ve
decided to remove the FK dependency detection logic altogether. This simplifies
the codebase.

Resolves: #159034
Release note: none

Author: spilchen

pkg/sql/logictest/testdata/logic_test/fk

@@ -4837,369 +4837,3 @@ DROP TABLE t2_fk;
 DROP TABLE t1_fk;
 
 subtest end
-
-subtest drop_col_dep_non_self_fk_stored
-
-# The logic in this UDF is equivalent to and originated from
-# columnDropViolatesFKIndexRequirements() in pkg/workload/schemachange/error_screening.go.
-statement ok
-CREATE FUNCTION column_drop_violates_fk_index_requirements(table_name STRING, column_name STRING)
-	RETURNS BOOL
-	LANGUAGE SQL
-	AS $$
-WITH fk AS (
-            SELECT oid,
-                   (
-                    SELECT r.relname
-                      FROM pg_class AS r
-                     WHERE r.oid = c.confrelid
-                   ) AS base_table,
-                   a.attname AS base_col,
-                   array_position(
-                    c.confkey,
-                    a.attnum
-                   ) AS base_ordinal,
-                   (
-                    SELECT r.relname
-                      FROM pg_class AS r
-                     WHERE r.oid = c.conrelid
-                   ) AS referencing_table,
-                   unnest(
-                    (
-                        SELECT array_agg(attname)
-                          FROM pg_attribute
-                         WHERE attrelid = c.conrelid
-                               AND ARRAY[attnum] <@ c.conkey
-                               AND array_position(
-                                    c.confkey,
-                                    a.attnum
-                                )
-                                = array_position(
-                                        c.conkey,
-                                        attnum
-                                    )
-                    )
-                   ) AS referencing_col
-              FROM pg_constraint AS c
-                   JOIN pg_attribute AS a ON c.confrelid
-                                                     = a.attrelid
-                                                     AND ARRAY[
-                                                            attnum
-                                                        ]
-                                                        <@ c.conkey
-             WHERE c.confrelid = table_name::REGCLASS::OID
-          ),
-       all_index_columns AS (
-                            SELECT
-                                i.indexrelid::REGCLASS::STRING
-                                    AS index_name,
-                                a.attname AS col_name,
-                                NOT
-                                    i.indisunique AS non_unique,
-                                a.attnum
-                                > i.indnkeyatts AS storing,
-                                a.attnum AS index_ordinal
-                            FROM
-                                pg_index AS i
-                                JOIN pg_attribute AS a ON
-                                        a.attrelid
-                                        = i.indexrelid
-                                        AND a.attnum > 0
-                            WHERE
-                                i.indrelid
-                                = table_name::REGCLASS::OID
-                         ),
-       valid_indexes AS (
-                        SELECT *
-                          FROM all_index_columns
-                         WHERE index_name
-                               NOT IN (
-                                    SELECT DISTINCT
-                                           index_name
-                                      FROM all_index_columns
-                                     WHERE col_name = column_name
-                                           AND index_name
-                                            NOT LIKE '%_pkey'
-                                )
-                     ),
-       fk_col_counts AS (
-                          SELECT oid, count(*) AS num_cols
-                            FROM fk
-                        GROUP BY oid
-                     ),
-              index_column_counts AS (
-       			SELECT index_name, count(*) as num_cols  FROM valid_indexes WHERE storing='f' GROUP BY index_name
-       		     ),
-              matching_fks AS (
-                                 SELECT fk.oid
-                                   FROM fk
-                                        JOIN valid_indexes ON
-                                               fk.base_col
-                                               = valid_indexes.col_name
-       				 JOIN index_column_counts ON
-       					valid_indexes.index_name = index_column_counts.index_name
-                                        JOIN fk_col_counts ON
-                                               fk.oid
-                                               = fk_col_counts.oid
-                                  WHERE valid_indexes.storing
-                                        = false
-                                        AND valid_indexes.non_unique
-                                           = false
-       				 AND index_column_counts.num_cols =  fk_col_counts.num_cols
-                               GROUP BY fk.oid,
-                                        valid_indexes.index_name,
-                                        fk_col_counts.num_cols
-                                 HAVING count(DISTINCT fk.base_col)
-                                        = fk_col_counts.num_cols
-                           )
-SELECT EXISTS(
-    SELECT *
-      FROM fk
-     WHERE oid NOT IN (SELECT DISTINCT oid FROM matching_fks)
-)
-$$;
-
-statement ok
-CREATE TABLE parent_dep_store (
-  id INT PRIMARY KEY,
-  key_col INT UNIQUE,
-  stored STRING,
-  FAMILY f1 (id, key_col, stored)
-) WITH (schema_locked = false);
-
-statement ok
-CREATE UNIQUE INDEX idx_parent_dep_store ON parent_dep_store (key_col) STORING (stored);
-
-statement ok
-CREATE TABLE child_dep_store (
-  id INT PRIMARY KEY,
-  parent_key INT REFERENCES parent_dep_store (key_col),
-  FAMILY f1 (id, parent_key)
-) WITH (schema_locked = false);
-
-query B
-SELECT column_drop_violates_fk_index_requirements('parent_dep_store', 'stored');
-----
-false
-
-statement ok
-ALTER TABLE parent_dep_store DROP COLUMN stored;
-
-query TT
-SHOW CREATE TABLE parent_dep_store
-----
-parent_dep_store  CREATE TABLE public.parent_dep_store (
-                    id INT8 NOT NULL,
-                    key_col INT8 NULL,
-                    CONSTRAINT parent_dep_store_pkey PRIMARY KEY (id ASC),
-                    UNIQUE INDEX parent_dep_store_key_col_key (key_col ASC),
-                    FAMILY f1 (id, key_col)
-                  );
-
-statement ok
-DROP TABLE child_dep_store;
-
-statement ok
-DROP TABLE parent_dep_store;
-
-subtest end
-
-subtest drop_col_dep_non_self_fk_key
-
-statement ok
-CREATE TABLE parent_dep_key (
-  id INT PRIMARY KEY,
-  key_col INT,
-  stored STRING,
-  FAMILY f1 (id, key_col, stored)
-) WITH (schema_locked = false);
-
-statement ok
-CREATE UNIQUE INDEX idx_parent_dep_key ON parent_dep_key (key_col) STORING (stored);
-
-statement ok
-CREATE TABLE child_dep_key (
-  id INT PRIMARY KEY,
-  parent_key INT REFERENCES parent_dep_key (key_col),
-  FAMILY f1 (id, parent_key)
-) WITH (schema_locked = false);
-
-query B
-SELECT column_drop_violates_fk_index_requirements('parent_dep_key', 'key_col');
-----
-true
-
-statement error pq: "idx_parent_dep_key" is referenced by foreign key from table "child_dep_key"
-ALTER TABLE parent_dep_key DROP COLUMN key_col;
-
-query TT
-SHOW CREATE TABLE parent_dep_key
-----
-parent_dep_key  CREATE TABLE public.parent_dep_key (
-                  id INT8 NOT NULL,
-                  key_col INT8 NULL,
-                  stored STRING NULL,
-                  CONSTRAINT parent_dep_key_pkey PRIMARY KEY (id ASC),
-                  UNIQUE INDEX idx_parent_dep_key (key_col ASC) STORING (stored),
-                  FAMILY f1 (id, key_col, stored)
-                );
-
-statement ok
-DROP TABLE child_dep_key;
-
-statement ok
-DROP TABLE parent_dep_key;
-
-subtest end
-
-subtest drop_col_dep_self_ref_stored
-
-statement ok
-CREATE TABLE self_dep_store (
-  id INT PRIMARY KEY,
-  ref INT,
-  stored STRING,
-  FAMILY f1 (id, ref, stored)
-) WITH (schema_locked = false);
-
-statement ok
-CREATE UNIQUE INDEX idx_self_dep_store ON self_dep_store (ref) STORING (stored);
-
-statement ok
-ALTER TABLE self_dep_store ADD CONSTRAINT fk_self_dep_store FOREIGN KEY (ref) REFERENCES self_dep_store (id);
-
-query B
-SELECT column_drop_violates_fk_index_requirements('self_dep_store', 'stored');
-----
-false
-
-statement ok
-ALTER TABLE self_dep_store DROP COLUMN stored;
-
-query TT
-SHOW CREATE TABLE self_dep_store
-----
-self_dep_store  CREATE TABLE public.self_dep_store (
-                  id INT8 NOT NULL,
-                  ref INT8 NULL,
-                  CONSTRAINT self_dep_store_pkey PRIMARY KEY (id ASC),
-                  CONSTRAINT fk_self_dep_store FOREIGN KEY (ref) REFERENCES public.self_dep_store(id),
-                  FAMILY f1 (id, ref)
-                );
-
-statement ok
-DROP TABLE self_dep_store;
-
-subtest end
-
-subtest drop_col_dep_self_ref_key
-
-statement ok
-CREATE TABLE self_dep_key (
-  id INT PRIMARY KEY,
-  ref INT,
-  stored STRING,
-  FAMILY f1 (id, ref, stored)
-) WITH (schema_locked = false);
-
-statement ok
-CREATE UNIQUE INDEX idx_self_dep_key ON self_dep_key (ref) STORING (stored);
-
-statement ok
-ALTER TABLE self_dep_key ADD CONSTRAINT fk_self_dep_key FOREIGN KEY (ref) REFERENCES self_dep_key (id);
-
-query B
-SELECT column_drop_violates_fk_index_requirements('self_dep_key', 'ref');
-----
-false
-
-statement ok
-ALTER TABLE self_dep_key DROP COLUMN ref;
-
-query TT
-SHOW CREATE TABLE self_dep_key
-----
-self_dep_key  CREATE TABLE public.self_dep_key (
-                id INT8 NOT NULL,
-                stored STRING NULL,
-                CONSTRAINT self_dep_key_pkey PRIMARY KEY (id ASC),
-                FAMILY f1 (id, stored)
-              );
-
-statement ok
-DROP TABLE self_dep_key;
-
-# Alternative secondary index has more storing columns, but has the correct key column
-# prefix to work.
-statement ok
-CREATE TABLE self_dep_key_2 (
-       col1_w4_6 INET NOT NULL,
-       col1_w4_7 DATE NOT NULL,
-       col1_w4_8 STRING COLLATE da_DK NOT NULL,
-       col1_w4_11 STRING NOT NULL,
-       col1_w4_13 INTERVAL NOT NULL,
-       col1_w4_14 UUID NOT NULL,
-       col1_w4_15 "char" NOT NULL,
-       CONSTRAINT table_w4_1_pkey PRIMARY KEY (col1_w4_6 ASC) USING HASH WITH (bucket_count=16),
-       CONSTRAINT table_w4_1_col1_w4_6_table_w4_1_col1_w4_6_fk FOREIGN KEY (col1_w4_6) REFERENCES self_dep_key_2 (col1_w4_6) ON DELETE CASCADE ON UPDATE CASCADE,
-       UNIQUE INDEX table_w4_1_col1_w4_6_key (col1_w4_6 ASC) STORING (col1_w4_7, col1_w4_11, col1_w4_13, col1_w4_14, col1_w4_15),
-       UNIQUE INDEX table_w4_1_col1_w4_6_col1_w4_8_key (col1_w4_6 ASC, col1_w4_8 DESC)
-   );
-
-query B
-SELECT column_drop_violates_fk_index_requirements('self_dep_key_2', 'col1_w4_8');
-----
-false
-
-# Sanity this should work.
-statement ok
-ALTER TABLE self_dep_key_2 DROP COLUMN col1_w4_8;
-
-
-# Self reference where dropping the stored column will be trouble.
-statement ok
-CREATE TABLE self_dep_key_3 (
-  id INT PRIMARY KEY,
-  indexed_col INT NOT NULL,
-  stored_col INT NOT NULL,
-  UNIQUE (indexed_col) STORING (stored_col)
-);
-
-statement ok
-ALTER TABLE self_dep_key_3 ADD CONSTRAINT t_fk
-  FOREIGN KEY (indexed_col) REFERENCES self_dep_key_3 (indexed_col);
-
-query B
-SELECT column_drop_violates_fk_index_requirements('self_dep_key_3', 'stored_col');
-----
-true
-
-# This should fail
-statement error pq: "self_dep_key_3_indexed_col_key" is referenced by foreign key from table "self_dep_key_3"
-ALTER TABLE self_dep_key_3 DROP COLUMN stored_col;
-
-# Self reference where dropping the stored column will lead to the only other
-# index not being usable (not the same prefix + length).
-statement ok
-CREATE TABLE self_dep_key_4 (
-  id INT PRIMARY KEY,
-  indexed_col INT NOT NULL,
-  stored_col INT NOT NULL,
-  UNIQUE (indexed_col) STORING (stored_col),
-  UNIQUE (indexed_col, id)
-);
-
-statement ok
-ALTER TABLE self_dep_key_4 ADD CONSTRAINT t_fk
-  FOREIGN KEY (indexed_col) REFERENCES self_dep_key_4 (indexed_col);
-
-query B
-SELECT column_drop_violates_fk_index_requirements('self_dep_key_4', 'stored_col');
-----
-true
-
-# This should fail
-statement error pq: "self_dep_key_4_indexed_col_key" is referenced by foreign key from table "self_dep_key_4"
-ALTER TABLE self_dep_key_4 DROP COLUMN stored_col;
-
-subtest end