Enable CHECK constraints to be declared NOT VALID

This means that they can initially be added to a large existing table
without checking its initial contents, but new tuples must comply to
them; a separate pass invoked by ALTER TABLE / VALIDATE can verify
existing data and ensure it complies with the constraint, at which point
it is marked validated and becomes a normal part of the table ecosystem.

An non-validated CHECK constraint is ignored in the planner for
constraint_exclusion purposes; when validated, cached plans are
recomputed so that partitioning starts working right away.

This patch also enables domains to have unvalidated CHECK constraints
attached to them as well by way of ALTER DOMAIN / ADD CONSTRAINT / NOT
VALID, which can later be validated with ALTER DOMAIN / VALIDATE
CONSTRAINT.

Thanks to Thom Brown, Dean Rasheed and Jaime Casanova for the various
reviews, and Robert Hass for documentation wording improvement
suggestions.

This patch was sponsored by Enova Financial.

4 files changed, 6 insertions, 0 deletions

diff --git a/src/include/access/tupdesc.h b/src/include/access/tupdesc.h
index 99448efe12f..8b99cb849d8 100644
--- a/src/include/access/tupdesc.h
+++ b/src/include/access/tupdesc.h
@@ -29,6 +29,7 @@ typedef struct constrCheck
 {
 	char	   *ccname;
 	char	   *ccbin;			/* nodeToString representation of expr */
+	bool		ccvalid;
 } ConstrCheck;
 
 /* This structure contains constraints of a tuple */
diff --git a/src/include/catalog/heap.h b/src/include/catalog/heap.h
index c95e91303b8..0b7b190dd10 100644
--- a/src/include/catalog/heap.h
+++ b/src/include/catalog/heap.h
@@ -30,6 +30,7 @@ typedef struct CookedConstraint
 	char	   *name;			/* name, or NULL if none */
 	AttrNumber	attnum;			/* which attr (only for DEFAULT) */
 	Node	   *expr;			/* transformed default or check expr */
+	bool		skip_validation;	/* skip validation? (only for CHECK) */
 	bool		is_local;		/* constraint has local (non-inherited) def */
 	int			inhcount;		/* number of times constraint is inherited */
 } CookedConstraint;
diff --git a/src/include/commands/typecmds.h b/src/include/commands/typecmds.h
index 6d9d1ccaa95..23726fb0fb2 100644
--- a/src/include/commands/typecmds.h
+++ b/src/include/commands/typecmds.h
@@ -31,6 +31,7 @@ extern Oid	AssignTypeArrayOid(void);
 extern void AlterDomainDefault(List *names, Node *defaultRaw);
 extern void AlterDomainNotNull(List *names, bool notNull);
 extern void AlterDomainAddConstraint(List *names, Node *constr);
+extern void AlterDomainValidateConstraint(List *names, char *constrName);
 extern void AlterDomainDropConstraint(List *names, const char *constrName,
 						  DropBehavior behavior);
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index c65e3cd6e8c..00c1269bd14 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1190,6 +1190,7 @@ typedef enum AlterTableType
 	AT_AddConstraint,			/* add constraint */
 	AT_AddConstraintRecurse,	/* internal to commands/tablecmds.c */
 	AT_ValidateConstraint,		/* validate constraint */
+	AT_ValidateConstraintRecurse, /* internal to commands/tablecmds.c */
 	AT_ProcessedConstraint,		/* pre-processed add constraint (local in
 								 * parser/parse_utilcmd.c) */
 	AT_AddIndexConstraint,		/* add constraint using existing index */
@@ -1543,6 +1544,8 @@ typedef struct Constraint
 	char		fk_matchtype;	/* FULL, PARTIAL, UNSPECIFIED */
 	char		fk_upd_action;	/* ON UPDATE action */
 	char		fk_del_action;	/* ON DELETE action */
+
+	/* Fields used for constraints that allow a NOT VALID specification */
 	bool		skip_validation;	/* skip validation of existing rows? */
 	bool		initially_valid;	/* mark the new constraint as valid? */
 } Constraint;