sql: get results of PRAGMA statement as result set

Currently box.sql.execute ('PRAGMA') returns nothing, but prints
list of pragmas and their statuses to stdout. Such strategy is
considered to be wrong since output of this command would be
unavailable for users who redirect stdout, use net box connection
etc. This patch makes the command to return result as the rest of
SQL commands. The result contains only FLAG-type pragmas and their
statuses.

src/box/sql/pragma.c

@@ -168,48 +168,26 @@ pragmaLocate(const char *zName)
 	return lwr > upr ? 0 : &aPragmaName[mid];
 }
 
-#ifdef PRINT_PRAGMA
-#undef PRINT_PRAGMA
-#endif
-#define PRINT_PRAGMA(pragma_name, pragma_flag) do {			       \
-	int nCoolSpaces = 30 - strlen(pragma_name);			       \
-	if (user_session->sql_flags & (pragma_flag)) {			       \
-		printf("%s %*c --  [true] \n", pragma_name, nCoolSpaces, ' '); \
-	} else {							       \
-		printf("%s %*c --  [false] \n", pragma_name, nCoolSpaces, ' ');\
-	}								       \
-} while (0)
-
-#define PRINT_STR_PRAGMA(pragma_name, str_value) do {			       \
-	int nCoolSpaces = 30 - strlen(pragma_name);			       \
-	printf("%s %*c --  '%s' \n", pragma_name, nCoolSpaces, ' ', str_value);\
-} while (0)
-
 static void
-printActivePragmas(struct session *user_session)
+vdbe_emit_pragma_status(struct Parse *parse)
 {
-	int i;
-	for (i = 0; i < ArraySize(aPragmaName); ++i) {
-		switch (aPragmaName[i].ePragTyp) {
-			case PragTyp_FLAG:
-				PRINT_PRAGMA(aPragmaName[i].zName, aPragmaName[i].iArg);
-				break;
-			case PragTyp_DEFAULT_ENGINE: {
-				const char *engine_name =
-					sql_storage_engine_strs[
-						current_session()->
-							sql_default_engine];
-				PRINT_STR_PRAGMA(aPragmaName[i].zName,
-						 engine_name);
-				break;
-			}
-		}
-	}
+	struct Vdbe *v = sqlGetVdbe(parse);
+	struct session *user_session = current_session();
+
+	sqlVdbeSetNumCols(v, 2);
+	sqlVdbeSetColName(v, 0, COLNAME_NAME, "pragma_name", SQL_STATIC);
+	sqlVdbeSetColName(v, 0, COLNAME_DECLTYPE, "TEXT", SQL_STATIC);
+	sqlVdbeSetColName(v, 1, COLNAME_NAME, "pragma_value", SQL_STATIC);
+	sqlVdbeSetColName(v, 1, COLNAME_DECLTYPE, "INTEGER", SQL_STATIC);
 
-	printf("Other available pragmas: \n");
-	for (i = 0; i < ArraySize(aPragmaName); ++i) {
+	parse->nMem = 2;
+	for (int i = 0; i < ArraySize(aPragmaName); ++i) {
 		if (aPragmaName[i].ePragTyp != PragTyp_FLAG)
-			printf("-- %s \n", aPragmaName[i].zName);
+			continue;
+		sqlVdbeAddOp4(v, OP_String8, 0, 1, 0, aPragmaName[i].zName, 0);
+		int val = (user_session->sql_flags & aPragmaName[i].iArg) != 0;
+		sqlVdbeAddOp2(v, OP_Integer, val, 2);
+		sqlVdbeAddOp2(v, OP_ResultRow, 1, 2);
 	}
 }
 
@@ -454,7 +432,7 @@ sqlPragma(Parse * pParse, Token * pId,	/* First part of [schema.]id field */
 
 	zLeft = sqlNameFromToken(db, pId);
 	if (!zLeft) {
-		printActivePragmas(user_session);
+		vdbe_emit_pragma_status(pParse);
 		return;
 	}
 

test/sql/sql-debug.result

@@ -21,3 +21,25 @@ box.sql.execute('PRAGMA parser_trace')
 box.sql.execute('PRAGMA parser_trace = '.. result[1][1])
 ---
 ...
+--
+-- Make PRAGMA command return the result as a result set.
+--
+box.sql.execute('PRAGMA')
+---
+- - ['case_sensitive_like', 0]
+  - ['count_changes', 0]
+  - ['defer_foreign_keys', 0]
+  - ['full_column_names', 0]
+  - ['parser_trace', 0]
+  - ['recursive_triggers', 1]
+  - ['reverse_unordered_selects', 0]
+  - ['select_trace', 0]
+  - ['short_column_names', 1]
+  - ['sql_trace', 0]
+  - ['vdbe_addoptrace', 0]
+  - ['vdbe_debug', 0]
+  - ['vdbe_eqp', 0]
+  - ['vdbe_listing', 0]
+  - ['vdbe_trace', 0]
+  - ['where_trace', 0]
+...

test/sql/sql-debug.test.lua

@@ -10,3 +10,8 @@ result = box.sql.execute('PRAGMA parser_trace')
 box.sql.execute('PRAGMA parser_trace = 1')
 box.sql.execute('PRAGMA parser_trace')
 box.sql.execute('PRAGMA parser_trace = '.. result[1][1])
+
+--
+-- Make PRAGMA command return the result as a result set.
+--
+box.sql.execute('PRAGMA')