Implement operator class parameters

PostgreSQL provides set of template index access methods, where opclasses have
much freedom in the semantics of indexing.  These index AMs are GiST, GIN,
SP-GiST and BRIN.  There opclasses define representation of keys, operations on
them and supported search strategies.  So, it's natural that opclasses may be
faced some tradeoffs, which require user-side decision.  This commit implements
opclass parameters allowing users to set some values, which tell opclass how to
index the particular dataset.

This commit doesn't introduce new storage in system catalog.  Instead it uses
pg_attribute.attoptions, which is used for table column storage options but
unused for index attributes.

In order to evade changing signature of each opclass support function, we
implement unified way to pass options to opclass support functions.  Options
are set to fn_expr as the constant bytea expression.  It's possible due to the
fact that opclass support functions are executed outside of expressions, so
fn_expr is unused for them.

This commit comes with some examples of opclass options usage.  We parametrize
signature length in GiST.  That applies to multiple opclasses: tsvector_ops,
gist__intbig_ops, gist_ltree_ops, gist__ltree_ops, gist_trgm_ops and
gist_hstore_ops.  Also we parametrize maximum number of integer ranges for
gist__int_ops.  However, the main future usage of this feature is expected
to be json, where users would be able to specify which way to index particular
json parts.

Catversion is bumped.

Discussion: https://postgr.es/m/d22c3a18-31c7-1879-fc11-4c1ce2f5e5af%40postgrespro.ru
Author: Nikita Glukhov, revised by me
Reviwed-by: Nikolay Shaplov, Robert Haas, Tom Lane, Tomas Vondra, Alvaro Herrera

src/include/access/amapi.h

@@ -171,6 +171,8 @@ typedef struct IndexAmRoutine
 	uint16		amstrategies;
 	/* total number of support functions that this AM uses */
 	uint16		amsupport;
+	/* opclass options support function number or 0 */
+	uint16		amoptsprocnum;
 	/* does AM support ORDER BY indexed column's value? */
 	bool		amcanorder;
 	/* does AM support ORDER BY result of an operator on indexed column? */

src/include/access/amvalidate.h

@@ -29,6 +29,7 @@ typedef struct OpFamilyOpFuncGroup
 extern List *identify_opfamily_groups(CatCList *oprlist, CatCList *proclist);
 extern bool check_amproc_signature(Oid funcid, Oid restype, bool exact,
 								   int minargs, int maxargs,...);
+extern bool check_amoptsproc_signature(Oid funcid);
 extern bool check_amop_signature(Oid opno, Oid restype,
 								 Oid lefttype, Oid righttype);
 extern bool opfamily_can_sort_type(Oid opfamilyoid, Oid datatypeoid);

src/include/access/brin_internal.h

@@ -69,6 +69,7 @@ typedef struct BrinDesc
 #define BRIN_PROCNUM_CONSISTENT		3
 #define BRIN_PROCNUM_UNION			4
 #define BRIN_MANDATORY_NPROCS		4
+#define BRIN_PROCNUM_OPTIONS 		5	/* optional */
 /* procedure numbers up to 10 are reserved for BRIN future expansion */
 #define BRIN_FIRST_OPTIONAL_PROCNUM 11
 #define BRIN_LAST_OPTIONAL_PROCNUM	15

src/include/access/genam.h

@@ -188,6 +188,9 @@ extern void index_store_float8_orderby_distances(IndexScanDesc scan,
 												 Oid *orderByTypes,
 												 IndexOrderByDistance *distances,
 												 bool recheckOrderBy);
+extern bytea *index_opclass_options(Relation relation, AttrNumber attnum,
+									Datum attoptions, bool validate);
+
 
 /*
  * index access method support routines (in genam.c)

src/include/access/gin.h

@@ -25,7 +25,8 @@
 #define GIN_CONSISTENT_PROC			   4
 #define GIN_COMPARE_PARTIAL_PROC	   5
 #define GIN_TRICONSISTENT_PROC		   6
-#define GINNProcs					   6
+#define GIN_OPTIONS_PROC	   7
+#define GINNProcs					   7
 
 /*
  * searchMode settings for extractQueryFn.

src/include/access/gist.h

@@ -16,6 +16,7 @@
 #ifndef GIST_H
 #define GIST_H
 
+#include "access/itup.h"
 #include "access/transam.h"
 #include "access/xlog.h"
 #include "access/xlogdefs.h"
@@ -35,7 +36,8 @@
 #define GIST_EQUAL_PROC					7
 #define GIST_DISTANCE_PROC				8
 #define GIST_FETCH_PROC					9
-#define GISTNProcs					9
+#define GIST_OPTIONS_PROC				10
+#define GISTNProcs						10
 
 /*
  * Page opaque data in a GiST index page.
@@ -73,6 +75,24 @@ typedef struct GISTPageOpaqueData
 
 typedef GISTPageOpaqueData *GISTPageOpaque;
 
+/*
+ * Maximum possible sizes for GiST index tuple and index key.  Calculation is
+ * based on assumption that GiST page should fit at least 4 tuples.  In theory,
+ * GiST index can be functional when page can fit 3 tuples.  But that seems
+ * rather inefficent, so we use a bit conservative estimate.
+ *
+ * The maximum size of index key is true for unicolumn index.  Therefore, this
+ * estimation should be used to figure out which maximum size of GiST index key
+ * makes sense at all.  For multicolumn indexes, user might be able to tune
+ * key size using opclass parameters.
+ */
+#define GISTMaxIndexTupleSize	\
+	MAXALIGN_DOWN((BLCKSZ - SizeOfPageHeaderData - sizeof(GISTPageOpaqueData)) / \
+				  4 - sizeof(ItemIdData))
+
+#define GISTMaxIndexKeySize	\
+	(GISTMaxIndexTupleSize - MAXALIGN(sizeof(IndexTupleData)))
+
 /*
  * The page ID is for the convenience of pg_filedump and similar utilities,
  * which otherwise would have a hard time telling pages of different index

src/include/access/hash.h

@@ -352,7 +352,8 @@ typedef struct HashOptions
  */
 #define HASHSTANDARD_PROC		1
 #define HASHEXTENDED_PROC		2
-#define HASHNProcs				2
+#define HASHOPTIONS_PROC		3
+#define HASHNProcs				3
 
 
 /* public routines */

src/include/access/nbtree.h

@@ -587,7 +587,8 @@ BTreeTupleGetMaxHeapTID(IndexTuple itup)
 #define BTSORTSUPPORT_PROC	2
 #define BTINRANGE_PROC		3
 #define BTEQUALIMAGE_PROC	4
-#define BTNProcs			4
+#define BTOPTIONS_PROC		5
+#define BTNProcs			5
 
 /*
  *	We need to be able to tell the difference between read and write

src/include/access/reloptions.h

@@ -38,6 +38,7 @@ typedef enum relopt_type
 /* kinds supported by reloptions */
 typedef enum relopt_kind
 {
+	RELOPT_KIND_LOCAL = 0,
 	RELOPT_KIND_HEAP = (1 << 0),
 	RELOPT_KIND_TOAST = (1 << 1),
 	RELOPT_KIND_BTREE = (1 << 2),
@@ -130,6 +131,10 @@ typedef struct relopt_enum
 
 /* validation routines for strings */
 typedef void (*validate_string_relopt) (const char *value);
+typedef Size (*fill_string_relopt) (const char *value, void *ptr);
+
+/* validation routine for the whole option set */
+typedef void (*relopts_validator) (void *parsed_options, relopt_value *vals, int nvals);
 
 typedef struct relopt_string
 {
@@ -137,6 +142,7 @@ typedef struct relopt_string
 	int			default_len;
 	bool		default_isnull;
 	validate_string_relopt validate_cb;
+	fill_string_relopt fill_cb;
 	char	   *default_val;
 } relopt_string;
 
@@ -148,6 +154,21 @@ typedef struct
 	int			offset;			/* offset of field in result struct */
 } relopt_parse_elt;
 
+/* Local reloption definition */
+typedef struct local_relopt
+{
+	relopt_gen *option;			/* option definition */
+	int			offset;			/* offset of parsed value in bytea structure */
+} local_relopt;
+
+/* Structure to hold local reloption data for build_local_reloptions() */
+typedef struct local_relopts
+{
+	List	   *options;		/* list of local_relopt definitions */
+	List	   *validators;		/* list of relopts_validator callbacks */
+	Size		relopt_struct_size; /* size of parsed bytea structure */
+} local_relopts;
+
 /*
  * Utility macro to get a value for a string reloption once the options
  * are parsed.  This gets a pointer to the string value itself.  "optstruct"
@@ -174,6 +195,30 @@ extern void add_string_reloption(bits32 kinds, const char *name, const char *des
 								 const char *default_val, validate_string_relopt validator,
 								 LOCKMODE lockmode);
 
+extern void init_local_reloptions(local_relopts *opts, Size relopt_struct_size);
+extern void register_reloptions_validator(local_relopts *opts,
+										  relopts_validator validator);
+extern void add_local_bool_reloption(local_relopts *opts, const char *name,
+									 const char *desc, bool default_val,
+									 int offset);
+extern void add_local_int_reloption(local_relopts *opts, const char *name,
+									const char *desc, int default_val,
+									int min_val, int max_val, int offset);
+extern void add_local_real_reloption(local_relopts *opts, const char *name,
+									 const char *desc, double default_val,
+									 double min_val, double max_val,
+									 int offset);
+extern void add_local_enum_reloption(local_relopts *relopts,
+									 const char *name, const char *desc,
+									 relopt_enum_elt_def *members,
+									 int default_val, const char *detailmsg,
+									 int offset);
+extern void add_local_string_reloption(local_relopts *opts, const char *name,
+									   const char *desc,
+									   const char *default_val,
+									   validate_string_relopt validator,
+									   fill_string_relopt filler, int offset);
+
 extern Datum transformRelOptions(Datum oldOptions, List *defList,
 								 const char *namspace, char *validnsps[],
 								 bool acceptOidsOff, bool isReset);
@@ -185,6 +230,8 @@ extern void *build_reloptions(Datum reloptions, bool validate,
 							  Size relopt_struct_size,
 							  const relopt_parse_elt *relopt_elems,
 							  int num_relopt_elems);
+extern void *build_local_reloptions(local_relopts *relopts, Datum options,
+									bool validate);
 
 extern bytea *default_reloptions(Datum reloptions, bool validate,
 								 relopt_kind kind);

src/include/access/spgist.h

@@ -26,8 +26,9 @@
 #define SPGIST_INNER_CONSISTENT_PROC	4
 #define SPGIST_LEAF_CONSISTENT_PROC		5
 #define SPGIST_COMPRESS_PROC			6
+#define SPGIST_OPTIONS_PROC				7
 #define SPGISTNRequiredProc				5
-#define SPGISTNProc						6
+#define SPGISTNProc						7
 
 /*
  * Argument structs for spg_config method