Support reloptions of enum type

All our current in core relation options of type string (not many,
admittedly) behave in reality like enums.  But after seeing an
implementation for enum reloptions, it's clear that strings are messier,
so introduce the new reloption type.  Switch all string options to be
enums instead.

Fortunately we have a recently introduced test module for reloptions, so
we don't lose coverage of string reloptions, which may still be used by
third-party modules.

Authors: Nikolay Shaplov, Álvaro Herrera
Reviewed-by: Nikita Glukhov, Aleksandr Parfenov
Discussion: https://postgr.es/m/43332102.S2V5pIjXRx@x200m

Author: alvherre

src/backend/access/common/reloptions.c

@@ -433,7 +433,25 @@ static relopt_real realRelOpts[] =
 	{{NULL}}
 };
 
-static relopt_string stringRelOpts[] =
+/* values from GistOptBufferingMode */
+relopt_enum_elt_def gistBufferingOptValues[] =
+{
+	{"auto", GIST_OPTION_BUFFERING_AUTO},
+	{"on", GIST_OPTION_BUFFERING_ON},
+	{"off", GIST_OPTION_BUFFERING_OFF},
+	{(const char *) NULL}		/* list terminator */
+};
+
+/* values from ViewOptCheckOption */
+relopt_enum_elt_def viewCheckOptValues[] =
+{
+	/* no value for NOT_SET */
+	{"local", VIEW_OPTION_CHECK_OPTION_LOCAL},
+	{"cascaded", VIEW_OPTION_CHECK_OPTION_CASCADED},
+	{(const char *) NULL}		/* list terminator */
+};
+
+static relopt_enum enumRelOpts[] =
 {
 	{
 		{
@@ -442,10 +460,9 @@ static relopt_string stringRelOpts[] =
 			RELOPT_KIND_GIST,
 			AccessExclusiveLock
 		},
-		4,
-		false,
-		gistValidateBufferingOption,
-		"auto"
+		gistBufferingOptValues,
+		GIST_OPTION_BUFFERING_AUTO,
+		gettext_noop("Valid values are \"on\", \"off\", and \"auto\".")
 	},
 	{
 		{
@@ -454,15 +471,20 @@ static relopt_string stringRelOpts[] =
 			RELOPT_KIND_VIEW,
 			AccessExclusiveLock
 		},
-		0,
-		true,
-		validateWithCheckOption,
-		NULL
+		viewCheckOptValues,
+		VIEW_OPTION_CHECK_OPTION_NOT_SET,
+		gettext_noop("Valid values are \"local\" and \"cascaded\".")
 	},
 	/* list terminator */
 	{{NULL}}
 };
 
+static relopt_string stringRelOpts[] =
+{
+	/* list terminator */
+	{{NULL}}
+};
+
 static relopt_gen **relOpts = NULL;
 static bits32 last_assigned_kind = RELOPT_KIND_LAST_DEFAULT;
 
@@ -505,6 +527,12 @@ initialize_reloptions(void)
 								   realRelOpts[i].gen.lockmode));
 		j++;
 	}
+	for (i = 0; enumRelOpts[i].gen.name; i++)
+	{
+		Assert(DoLockModesConflict(enumRelOpts[i].gen.lockmode,
+								   enumRelOpts[i].gen.lockmode));
+		j++;
+	}
 	for (i = 0; stringRelOpts[i].gen.name; i++)
 	{
 		Assert(DoLockModesConflict(stringRelOpts[i].gen.lockmode,
@@ -543,6 +571,14 @@ initialize_reloptions(void)
 		j++;
 	}
 
+	for (i = 0; enumRelOpts[i].gen.name; i++)
+	{
+		relOpts[j] = &enumRelOpts[i].gen;
+		relOpts[j]->type = RELOPT_TYPE_ENUM;
+		relOpts[j]->namelen = strlen(relOpts[j]->name);
+		j++;
+	}
+
 	for (i = 0; stringRelOpts[i].gen.name; i++)
 	{
 		relOpts[j] = &stringRelOpts[i].gen;
@@ -641,6 +677,9 @@ allocate_reloption(bits32 kinds, int type, const char *name, const char *desc,
 		case RELOPT_TYPE_REAL:
 			size = sizeof(relopt_real);
 			break;
+		case RELOPT_TYPE_ENUM:
+			size = sizeof(relopt_enum);
+			break;
 		case RELOPT_TYPE_STRING:
 			size = sizeof(relopt_string);
 			break;
@@ -661,6 +700,13 @@ allocate_reloption(bits32 kinds, int type, const char *name, const char *desc,
 	newoption->type = type;
 	newoption->lockmode = lockmode;
 
+	/*
+	 * Set the default lock mode for this option.  There is no actual way
+	 * for a module to enforce it when declaring a custom relation option,
+	 * so just use the highest level, which is safe for all cases.
+	 */
+	newoption->lockmode = AccessExclusiveLock;
+
 	MemoryContextSwitchTo(oldcxt);
 
 	return newoption;
@@ -721,6 +767,34 @@ add_real_reloption(bits32 kinds, const char *name, const char *desc, double defa
 	add_reloption((relopt_gen *) newoption);
 }
 
+/*
+ * add_enum_reloption
+ *		Add a new enum reloption
+ *
+ * The members array must have a terminating NULL entry.
+ *
+ * The detailmsg is shown when unsupported values are passed, and has this
+ * form:   "Valid values are \"foo\", \"bar\", and \"bar\"."
+ *
+ * The members array and detailmsg are not copied -- caller must ensure that
+ * they are valid throughout the life of the process.
+ */
+void
+add_enum_reloption(bits32 kinds, const char *name, const char *desc,
+				   relopt_enum_elt_def *members, int default_val,
+				   const char *detailmsg, LOCKMODE lockmode)
+{
+	relopt_enum *newoption;
+
+	newoption = (relopt_enum *) allocate_reloption(kinds, RELOPT_TYPE_ENUM,
+												   name, desc, lockmode);
+	newoption->members = members;
+	newoption->default_val = default_val;
+	newoption->detailmsg = detailmsg;
+
+	add_reloption((relopt_gen *) newoption);
+}
+
 /*
  * add_string_reloption
  *		Add a new string reloption
@@ -1237,6 +1311,37 @@ parse_one_reloption(relopt_value *option, char *text_str, int text_len,
 									   optreal->min, optreal->max)));
 			}
 			break;
+		case RELOPT_TYPE_ENUM:
+			{
+				relopt_enum *optenum = (relopt_enum *) option->gen;
+				relopt_enum_elt_def *elt;
+
+				parsed = false;
+				for (elt = optenum->members; elt->string_val; elt++)
+				{
+					if (pg_strcasecmp(value, elt->string_val) == 0)
+					{
+						option->values.enum_val = elt->symbol_val;
+						parsed = true;
+						break;
+					}
+				}
+				if (validate && !parsed)
+					ereport(ERROR,
+							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+							 errmsg("invalid value for enum option \"%s\": %s",
+									option->gen->name, value),
+							 optenum->detailmsg ?
+							 errdetail_internal("%s", _(optenum->detailmsg)) : 0));
+
+				/*
+				 * If value is not among the allowed string values, but we are
+				 * not asked to validate, just use the default numeric value.
+				 */
+				if (!parsed)
+					option->values.enum_val = optenum->default_val;
+			}
+			break;
 		case RELOPT_TYPE_STRING:
 			{
 				relopt_string *optstring = (relopt_string *) option->gen;
@@ -1330,6 +1435,11 @@ fillRelOptions(void *rdopts, Size basesize,
 							options[i].values.real_val :
 							((relopt_real *) options[i].gen)->default_val;
 						break;
+					case RELOPT_TYPE_ENUM:
+						*(int *) itempos = options[i].isset ?
+							options[i].values.enum_val :
+							((relopt_enum *) options[i].gen)->default_val;
+						break;
 					case RELOPT_TYPE_STRING:
 						optstring = (relopt_string *) options[i].gen;
 						if (options[i].isset)
@@ -1446,8 +1556,8 @@ view_reloptions(Datum reloptions, bool validate)
 	static const relopt_parse_elt tab[] = {
 		{"security_barrier", RELOPT_TYPE_BOOL,
 		offsetof(ViewOptions, security_barrier)},
-		{"check_option", RELOPT_TYPE_STRING,
-		offsetof(ViewOptions, check_option_offset)}
+		{"check_option", RELOPT_TYPE_ENUM,
+		offsetof(ViewOptions, check_option)}
 	};
 
 	options = parseRelOptions(reloptions, validate, RELOPT_KIND_VIEW, &numoptions);

src/backend/access/gist/gistbuild.c

@@ -125,15 +125,15 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 
 	buildstate.indexrel = index;
 	buildstate.heaprel = heap;
+
 	if (index->rd_options)
 	{
 		/* Get buffering mode from the options string */
 		GiSTOptions *options = (GiSTOptions *) index->rd_options;
-		char	   *bufferingMode = (char *) options + options->bufferingModeOffset;
 
-		if (strcmp(bufferingMode, "on") == 0)
+		if (options->buffering_mode == GIST_OPTION_BUFFERING_ON)
 			buildstate.bufferingMode = GIST_BUFFERING_STATS;
-		else if (strcmp(bufferingMode, "off") == 0)
+		else if (options->buffering_mode == GIST_OPTION_BUFFERING_OFF)
 			buildstate.bufferingMode = GIST_BUFFERING_DISABLED;
 		else
 			buildstate.bufferingMode = GIST_BUFFERING_AUTO;
@@ -236,25 +236,6 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	return result;
 }
 
-/*
- * Validator for "buffering" reloption on GiST indexes. Allows "on", "off"
- * and "auto" values.
- */
-void
-gistValidateBufferingOption(const char *value)
-{
-	if (value == NULL ||
-		(strcmp(value, "on") != 0 &&
-		 strcmp(value, "off") != 0 &&
-		 strcmp(value, "auto") != 0))
-	{
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("invalid value for \"buffering\" option"),
-				 errdetail("Valid values are \"on\", \"off\", and \"auto\".")));
-	}
-}
-
 /*
  * Attempt to switch to buffering mode.
  *

src/backend/access/gist/gistutil.c

@@ -913,7 +913,7 @@ gistoptions(Datum reloptions, bool validate)
 	int			numoptions;
 	static const relopt_parse_elt tab[] = {
 		{"fillfactor", RELOPT_TYPE_INT, offsetof(GiSTOptions, fillfactor)},
-		{"buffering", RELOPT_TYPE_STRING, offsetof(GiSTOptions, bufferingModeOffset)}
+		{"buffering", RELOPT_TYPE_ENUM, offsetof(GiSTOptions, buffering_mode)}
 	};
 
 	options = parseRelOptions(reloptions, validate, RELOPT_KIND_GIST,

src/backend/commands/view.c

@@ -38,24 +38,6 @@
 
 static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc);
 
-/*---------------------------------------------------------------------
- * Validator for "check_option" reloption on views. The allowed values
- * are "local" and "cascaded".
- */
-void
-validateWithCheckOption(const char *value)
-{
-	if (value == NULL ||
-		(strcmp(value, "local") != 0 &&
-		 strcmp(value, "cascaded") != 0))
-	{
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("invalid value for \"check_option\" option"),
-				 errdetail("Valid values are \"local\" and \"cascaded\".")));
-	}
-}
-
 /*---------------------------------------------------------------------
  * DefineVirtualRelation
  *

src/include/access/gist_private.h

@@ -380,14 +380,22 @@ typedef struct GISTBuildBuffers
 	int			rootlevel;
 } GISTBuildBuffers;
 
+/* GiSTOptions->buffering_mode values */
+typedef enum GistOptBufferingMode
+{
+	GIST_OPTION_BUFFERING_AUTO,
+	GIST_OPTION_BUFFERING_ON,
+	GIST_OPTION_BUFFERING_OFF
+} GistOptBufferingMode;
+
 /*
  * Storage type for GiST's reloptions
  */
 typedef struct GiSTOptions
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	int			fillfactor;		/* page fill factor in percent (0..100) */
-	int			bufferingModeOffset;	/* use buffering build? */
+	GistOptBufferingMode buffering_mode;	/* buffering build mode */
 } GiSTOptions;
 
 /* gist.c */

src/include/access/reloptions.h

@@ -31,6 +31,7 @@ typedef enum relopt_type
 	RELOPT_TYPE_BOOL,
 	RELOPT_TYPE_INT,
 	RELOPT_TYPE_REAL,
+	RELOPT_TYPE_ENUM,
 	RELOPT_TYPE_STRING
 } relopt_type;
 
@@ -80,6 +81,7 @@ typedef struct relopt_value
 		bool		bool_val;
 		int			int_val;
 		double		real_val;
+		int			enum_val;
 		char	   *string_val; /* allocated separately */
 	}			values;
 } relopt_value;
@@ -107,6 +109,25 @@ typedef struct relopt_real
 	double		max;
 } relopt_real;
 
+/*
+ * relopt_enum_elt_def -- One member of the array of acceptable values
+ * of an enum reloption.
+ */
+typedef struct relopt_enum_elt_def
+{
+	const char *string_val;
+	int			symbol_val;
+} relopt_enum_elt_def;
+
+typedef struct relopt_enum
+{
+	relopt_gen	gen;
+	relopt_enum_elt_def *members;
+	int			default_val;
+	const char *detailmsg;
+	/* null-terminated array of members */
+} relopt_enum;
+
 /* validation routines for strings */
 typedef void (*validate_string_relopt) (const char *value);
 
@@ -254,6 +275,9 @@ extern void add_int_reloption(bits32 kinds, const char *name, const char *desc,
 extern void add_real_reloption(bits32 kinds, const char *name, const char *desc,
 							   double default_val, double min_val, double max_val,
 							   LOCKMODE lockmode);
+extern void add_enum_reloption(bits32 kinds, const char *name, const char *desc,
+							   relopt_enum_elt_def *members, int default_val,
+							   const char *detailmsg, LOCKMODE lockmode);
 extern void add_string_reloption(bits32 kinds, const char *name, const char *desc,
 								 const char *default_val, validate_string_relopt validator,
 								 LOCKMODE lockmode);

src/include/commands/view.h

@@ -17,8 +17,6 @@
 #include "catalog/objectaddress.h"
 #include "nodes/parsenodes.h"
 
-extern void validateWithCheckOption(const char *value);
-
 extern ObjectAddress DefineView(ViewStmt *stmt, const char *queryString,
 								int stmt_location, int stmt_len);