Remove blocker for unique constraints with ADD COLUMN

Remove special handling for ADD COLUMN with unique/primary key
constraints on compressed hypertables. This patch makes the behaviour
consistent with uncompressed hypertable where ADD COLUMN with unique/
primary key constraint is blocked because those constraints require
all partitioning columns to be included.

Author: svenklemm

.unreleased/pr_7877

@@ -0,0 +1 @@
+Implements: #7877 Remove blocker for unique constraints with ADD COLUMN

src/process_utility.c

@@ -327,6 +327,14 @@ check_altertable_add_column_for_compressed(Hypertable *ht, ColumnDef *col)
 			Constraint *constraint = lfirst_node(Constraint, lc);
 			switch (constraint->contype)
 			{
+				/*
+				 * These will fail in combination with ADD COLUMN because this will
+				 * be a single column constraint and we require all partitioning
+				 * columns to be part if the unique/primary key constraint.
+				 */
+				case CONSTR_PRIMARY:
+				case CONSTR_UNIQUE:
+					break;
 				/*
 				 * We can safelly ignore NULL constraints because it does nothing
 				 * and according to Postgres docs is useless and exist just for

tsl/test/expected/compression_errors.out

@@ -366,9 +366,11 @@ alter table table_constr drop constraint table_constr_exclu ;
 ALTER TABLE table_constr set (timescaledb.compress, timescaledb.compress_orderby = 'timec', timescaledb.compress_segmentby = 'device_id, location, d');
 -- ddl ADD column variants that are not supported
 ALTER TABLE table_constr ADD COLUMN newcol integer UNIQUE;
-ERROR:  cannot add column with constraints to a hypertable that has compression enabled
+ERROR:  cannot create a unique index without the column "timec" (used in partitioning)
+HINT:  If you're creating a hypertable on a table with a primary key, ensure the partitioning column is part of the primary or composite key.
 ALTER TABLE table_constr ADD COLUMN newcol integer PRIMARY KEY;
-ERROR:  cannot add column with constraints to a hypertable that has compression enabled
+ERROR:  cannot create a unique index without the column "timec" (used in partitioning)
+HINT:  If you're creating a hypertable on a table with a primary key, ensure the partitioning column is part of the primary or composite key.
 ALTER TABLE table_constr ADD COLUMN newcol integer NOT NULL;
 ERROR:  cannot add column with NOT NULL constraint without default to a hypertable that has compression enabled
 ALTER TABLE table_constr ADD COLUMN newcol integer DEFAULT random() + random();