Support CREATE ACCESS METHOD

This enables external code to create access methods.  This is useful so
that extensions can add their own access methods which can be formally
tracked for dependencies, so that DROP operates correctly.  Also, having
explicit support makes pg_dump work correctly.

Currently only index AMs are supported, but we expect different types to
be added in the future.

Authors: Alexander Korotkov, Petr Jelínek
Reviewed-By: Teodor Sigaev, Petr Jelínek, Jim Nasby
Commitfest-URL: https://commitfest.postgresql.org/9/353/
Discussion: https://www.postgresql.org/message-id/CAPpHfdsXwZmojm6Dx+TJnpYk27kT4o7Ri6X_4OSWcByu1Rm+VA@mail.gmail.com

8 files changed, 87 insertions, 10 deletions

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 3568cb27e81..b690dc6b34f 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201603211
+#define CATALOG_VERSION_NO	201603231
 
 #endif
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 049bf9f5a2e..d41abc4e480 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -134,6 +134,7 @@ typedef enum ObjectClass
 	OCLASS_OPERATOR,			/* pg_operator */
 	OCLASS_OPCLASS,				/* pg_opclass */
 	OCLASS_OPFAMILY,			/* pg_opfamily */
+	OCLASS_AM,					/* pg_am */
 	OCLASS_AMOP,				/* pg_amop */
 	OCLASS_AMPROC,				/* pg_amproc */
 	OCLASS_REWRITE,				/* pg_rewrite */
diff --git a/src/include/catalog/pg_am.h b/src/include/catalog/pg_am.h
index f801c3ee577..11169237991 100644
--- a/src/include/catalog/pg_am.h
+++ b/src/include/catalog/pg_am.h
@@ -35,6 +35,7 @@ CATALOG(pg_am,2601)
 {
 	NameData	amname;			/* access method name */
 	regproc		amhandler;		/* handler function */
+	char		amtype;			/* see AMTYPE_xxx constants below */
 } FormData_pg_am;
 
 /* ----------------
@@ -48,31 +49,38 @@ typedef FormData_pg_am *Form_pg_am;
  *		compiler constants for pg_am
  * ----------------
  */
-#define Natts_pg_am						2
+#define Natts_pg_am						3
 #define Anum_pg_am_amname				1
 #define Anum_pg_am_amhandler			2
+#define Anum_pg_am_amtype				3
+
+/* ----------------
+ *		compiler constant for amtype
+ * ----------------
+ */
+#define AMTYPE_INDEX					'i'		/* index access method */
 
 /* ----------------
  *		initial contents of pg_am
  * ----------------
  */
 
-DATA(insert OID = 403 (  btree		bthandler ));
+DATA(insert OID = 403 (  btree		bthandler	i ));
 DESCR("b-tree index access method");
 #define BTREE_AM_OID 403
-DATA(insert OID = 405 (  hash		hashhandler ));
+DATA(insert OID = 405 (  hash		hashhandler i ));
 DESCR("hash index access method");
 #define HASH_AM_OID 405
-DATA(insert OID = 783 (  gist		gisthandler ));
+DATA(insert OID = 783 (  gist		gisthandler i ));
 DESCR("GiST index access method");
 #define GIST_AM_OID 783
-DATA(insert OID = 2742 (  gin		ginhandler ));
+DATA(insert OID = 2742 (  gin		ginhandler	i ));
 DESCR("GIN index access method");
 #define GIN_AM_OID 2742
-DATA(insert OID = 4000 (  spgist	spghandler ));
+DATA(insert OID = 4000 (  spgist	spghandler	i ));
 DESCR("SP-GiST index access method");
 #define SPGIST_AM_OID 4000
-DATA(insert OID = 3580 (  brin		brinhandler ));
+DATA(insert OID = 3580 (  brin		brinhandler i ));
 DESCR("block range index (BRIN) access method");
 #define BRIN_AM_OID 3580
 
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index 54f67e9eea6..b064eb4836a 100644
--- a/src/include/commands/defrem.h
+++ b/src/include/commands/defrem.h
@@ -91,8 +91,6 @@ extern void IsThereOpClassInNamespace(const char *opcname, Oid opcmethod,
 						  Oid opcnamespace);
 extern void IsThereOpFamilyInNamespace(const char *opfname, Oid opfmethod,
 						   Oid opfnamespace);
-extern Oid	get_am_oid(const char *amname, bool missing_ok);
-extern char *get_am_name(Oid amOid);
 extern Oid	get_opclass_oid(Oid amID, List *opclassname, bool missing_ok);
 extern Oid	get_opfamily_oid(Oid amID, List *opfamilyname, bool missing_ok);
 
@@ -137,6 +135,13 @@ extern Datum transformGenericOptions(Oid catalogId,
 						List *options,
 						Oid fdwvalidator);
 
+/* commands/amcmds.c */
+extern ObjectAddress CreateAccessMethod(CreateAmStmt *stmt);
+extern void RemoveAccessMethodById(Oid amOid);
+extern Oid	get_index_am_oid(const char *amname, bool missing_ok);
+extern Oid	get_am_oid(const char *amname, bool missing_ok);
+extern char *get_am_name(Oid amOid);
+
 /* support routines in commands/define.c */
 
 extern char *defGetString(DefElem *def);
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 42c958258b6..734df771eb2 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -402,6 +402,7 @@ typedef enum NodeTag
 	T_CreatePolicyStmt,
 	T_AlterPolicyStmt,
 	T_CreateTransformStmt,
+	T_CreateAmStmt,
 
 	/*
 	 * TAGS FOR PARSE TREE NODES (parsenodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 2fd06295e5c..8b958b422cb 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1379,6 +1379,7 @@ typedef struct SetOperationStmt
 
 typedef enum ObjectType
 {
+	OBJECT_ACCESS_METHOD,
 	OBJECT_AGGREGATE,
 	OBJECT_AMOP,
 	OBJECT_AMPROC,
@@ -2070,6 +2071,18 @@ typedef struct AlterPolicyStmt
 	Node	   *with_check;		/* the policy's WITH CHECK condition. */
 } AlterPolicyStmt;
 
+/*----------------------
+ *		Create ACCESS METHOD Statement
+ *----------------------
+ */
+typedef struct CreateAmStmt
+{
+	NodeTag		type;
+	char	   *amname;			/* access method name */
+	List	   *handler_name;	/* handler function name */
+	char		amtype;			/* type of access method */
+} CreateAmStmt;
+
 /* ----------------------
  *		Create TRIGGER Statement
  * ----------------------
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 6e1e82027cb..7de3404aa22 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -239,6 +239,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/include/utils/selfuncs.h b/src/include/utils/selfuncs.h
index 06fbca719b5..8e0d3174687 100644
--- a/src/include/utils/selfuncs.h
+++ b/src/include/utils/selfuncs.h
@@ -95,6 +95,48 @@ typedef enum
 	Pattern_Prefix_None, Pattern_Prefix_Partial, Pattern_Prefix_Exact
 } Pattern_Prefix_Status;
 
+/*
+ * deconstruct_indexquals is a simple function to examine the indexquals
+ * attached to a proposed IndexPath.  It returns a list of IndexQualInfo
+ * structs, one per qual expression.
+ */
+typedef struct
+{
+	RestrictInfo *rinfo;		/* the indexqual itself */
+	int			indexcol;		/* zero-based index column number */
+	bool		varonleft;		/* true if index column is on left of qual */
+	Oid			clause_op;		/* qual's operator OID, if relevant */
+	Node	   *other_operand;	/* non-index operand of qual's operator */
+} IndexQualInfo;
+
+/*
+ * genericcostestimate is a general-purpose estimator that can be used for
+ * most index types.  In some cases we use genericcostestimate as the base
+ * code and then incorporate additional index-type-specific knowledge in
+ * the type-specific calling function.  To avoid code duplication, we make
+ * genericcostestimate return a number of intermediate values as well as
+ * its preliminary estimates of the output cost values.  The GenericCosts
+ * struct includes all these values.
+ *
+ * Callers should initialize all fields of GenericCosts to zero.  In addition,
+ * they can set numIndexTuples to some positive value if they have a better
+ * than default way of estimating the number of leaf index tuples visited.
+ */
+typedef struct
+{
+	/* These are the values the cost estimator must return to the planner */
+	Cost		indexStartupCost;		/* index-related startup cost */
+	Cost		indexTotalCost; /* total index-related scan cost */
+	Selectivity indexSelectivity;		/* selectivity of index */
+	double		indexCorrelation;		/* order correlation of index */
+
+	/* Intermediate values we obtain along the way */
+	double		numIndexPages;	/* number of leaf pages visited */
+	double		numIndexTuples; /* number of leaf tuples visited */
+	double		spc_random_page_cost;	/* relevant random_page_cost value */
+	double		num_sa_scans;	/* # indexscans from ScalarArrayOps */
+} GenericCosts;
+
 /* Hooks for plugins to get control when we ask for stats */
 typedef bool (*get_relation_stats_hook_type) (PlannerInfo *root,
 														  RangeTblEntry *rte,
@@ -191,6 +233,12 @@ extern double estimate_num_groups(PlannerInfo *root, List *groupExprs,
 extern Selectivity estimate_hash_bucketsize(PlannerInfo *root, Node *hashkey,
 						 double nbuckets);
 
+extern List *deconstruct_indexquals(IndexPath *path);
+extern void genericcostestimate(PlannerInfo *root, IndexPath *path,
+					double loop_count,
+					List *qinfos,
+					GenericCosts *costs);
+
 /* Functions in array_selfuncs.c */
 
 extern Selectivity scalararraysel_containment(PlannerInfo *root,