本节继续介绍PostgreSQL的语法分析定义文件gram.y的第二部分Definitions. Bison输入文件的组成: ``` %{ Declarations %} Definitions %% Productions %% User subroutines ``` ### 一、Definitions Definitions在Bison的作用与Flex中的功能也差不多,在这个段定义一些Bison专有变量或相关选项. **%purge-parser** 指示Bison创建一个可重入的解析器.与普通的解析器一个很大的不同的,yylval的类型是union指针而不是union. **%expect** %expect N告诉Bison，解析器应该有N个shift/reduce冲突，如果不匹配，Bison将报告编译时错误。 **%name-prefix** 命名函数名称,默认为yy %name-prefix "base_yy"意味着默认的yyxx()会变成base_yyxx().比如yyparse(),yylex(),yyerror(),yylval,yychar和 yydebug. **%locations** 位置 **%parse-param** %parse-param声明的内容位于yyparse()的括号之间,可以声明任意多的参数. 比如%parse-param {core_yyscan_t yyscanner},参数为core_yyscan_t yyscanner. **%lex-param** %lex-param声明的内容位于yylex()的括号之间,可以声明任意多的参数. 比如%lex-param {core_yyscan_t yyscanner},参数为core_yyscan_t yyscanner. **%union** %union声明了在解析器中标识符所使用的类型. Bison解析器,每一个标识符,包括tokens和非终结符,都有值与之关联,默认的,值的类型都是整型,但在实际应用中远远不够. %union可以为标识符值创建C语言union声明. ``` %union { core_YYSTYPE core_yystype; /* these fields must match core_YYSTYPE: */ int ival; char *str; const char *keyword; ... } ``` 其中core_yystype的类型为core_YYSTYPE联合体. ``` /* * The scanner returns extra data about scanned tokens in this union type. * Note that this is a subset of the fields used in YYSTYPE of the bison * parsers built atop the scanner. */ typedef union core_YYSTYPE { int ival; /* for integer literals */ char *str; /* for identifiers and non-integer literals */ const char *keyword; /* canonical spelling of keywords */ } core_YYSTYPE; ``` 一旦定义了union,那需要通过将union中合适的名称放在尖括号(<>)中,用以告诉Bison哪些符号具有哪些类型的值. **%type** 类型定义,如: ``` %type <node> stmt schema_stmt AlterEventTrigStmt AlterCollationStmt ... ``` 表示标识符/非终结符<node>的类型可以是stmt/schema_stmt/AlterEventTrigStmt/... **%nonassoc** 使用%nonassoc声明非关联操作符。 **%left** 左关联操作符 **%right** 右关联操作符 ### 二、gram.y定义部分源码 ``` %pure-parser %expect 0 %name-prefix="base_yy" %locations %parse-param {core_yyscan_t yyscanner} %lex-param {core_yyscan_t yyscanner} %union { core_YYSTYPE core_yystype; /* these fields must match core_YYSTYPE: */ int ival; char *str; const char *keyword; char chr; bool boolean; JoinType jtype; DropBehavior dbehavior; OnCommitAction oncommit; List *list; Node *node; Value *value; ObjectType objtype; TypeName *typnam; FunctionParameter *fun_param; FunctionParameterMode fun_param_mode; ObjectWithArgs *objwithargs; DefElem *defelt; SortBy *sortby; WindowDef *windef; JoinExpr *jexpr; IndexElem *ielem; Alias *alias; RangeVar *range; IntoClause *into; WithClause *with; InferClause *infer; OnConflictClause *onconflict; A_Indices *aind; ResTarget *target; struct PrivTarget *privtarget; AccessPriv *accesspriv; struct ImportQual *importqual; InsertStmt *istmt; VariableSetStmt *vsetstmt; PartitionElem *partelem; PartitionSpec *partspec; PartitionBoundSpec *partboundspec; RoleSpec *rolespec; } %type <node> stmt schema_stmt AlterEventTrigStmt AlterCollationStmt AlterDatabaseStmt AlterDatabaseSetStmt AlterDomainStmt AlterEnumStmt AlterFdwStmt AlterForeignServerStmt AlterGroupStmt AlterObjectDependsStmt AlterObjectSchemaStmt AlterOwnerStmt AlterOperatorStmt AlterSeqStmt AlterSystemStmt AlterTableStmt AlterTblSpcStmt AlterExtensionStmt AlterExtensionContentsStmt AlterForeignTableStmt AlterCompositeTypeStmt AlterUserMappingStmt AlterRoleStmt AlterRoleSetStmt AlterPolicyStmt AlterDefaultPrivilegesStmt DefACLAction AnalyzeStmt CallStmt ClosePortalStmt ClusterStmt CommentStmt ConstraintsSetStmt CopyStmt CreateAsStmt CreateCastStmt CreateDomainStmt CreateExtensionStmt CreateGroupStmt CreateOpClassStmt CreateOpFamiXXXtmt AlterOpFamiXXXtmt CreatePLangStmt CreateSchemaStmt CreateSeqStmt CreateStmt CreateStatsStmt CreateTableSpaceStmt CreateFdwStmt CreateForeignServerStmt CreateForeignTableStmt CreateAssertStmt CreateTransformStmt CreateTrigStmt CreateEventTrigStmt CreateUserStmt CreateUserMappingStmt CreateRoleStmt CreatePolicyStmt CreatedbStmt DeclareCursorStmt DefineStmt DeleteStmt DiscardStmt DoStmt DropOpClassStmt DropOpFamiXXXtmt DropPLangStmt DropStmt DropAssertStmt DropCastStmt DropRoleStmt DropdbStmt DropTableSpaceStmt DropTransformStmt DropUserMappingStmt ExplainStmt FetchStmt GrantStmt GrantRoleStmt ImportForeignSchemaStmt IndexStmt InsertStmt ListenStmt LoadStmt LockStmt NotifyStmt ExplainableStmt PreparableStmt CreateFunctionStmt AlterFunctionStmt ReindexStmt RemoveAggrStmt RemoveFuncStmt RemoveOperStmt RenameStmt RevokeStmt RevokeRoleStmt RuleActionStmt RuleActionStmtOrEmpty RuleStmt SecLabelStmt SelectStmt TransactionStmt TruncateStmt UnlistenStmt UpdateStmt VacuumStmt VariableResetStmt VariableSetStmt VariableShowStmt ViewStmt CheckPointStmt CreateConversionStmt DeallocateStmt PrepareStmt ExecuteStmt DropOwnedStmt ReassignOwnedStmt AlterTSConfigurationStmt AlterTSDictionaryStmt CreateMatViewStmt RefreshMatViewStmt CreateAmStmt CreatePublicationStmt AlterPublicationStmt CreateSubscriptionStmt AlterSubscriptionStmt DropSubscriptionStmt %type <node> select_no_parens select_with_parens select_clause simple_select values_clause %type <node> alter_column_default opclass_item opclass_drop alter_using %type <ival> add_drop opt_asc_desc opt_nulls_order %type <node> alter_table_cmd alter_type_cmd opt_collate_clause replica_identity partition_cmd index_partition_cmd %type <list> alter_table_cmds alter_type_cmds %type <list> alter_identity_column_option_list %type <defelt> alter_identity_column_option %type <dbehavior> opt_drop_behavior %type <list> createdb_opt_list createdb_opt_items copy_opt_list transaction_mode_list create_extension_opt_list alter_extension_opt_list %type <defelt> createdb_opt_item copy_opt_item transaction_mode_item create_extension_opt_item alter_extension_opt_item %type <ival> opt_lock lock_type cast_context %type <ival> vacuum_option_list vacuum_option_elem analyze_option_list analyze_option_elem %type <boolean> opt_or_replace opt_grant_grant_option opt_grant_admin_option opt_nowait opt_if_exists opt_with_data %type <ival> opt_nowait_or_skip %type <list> OptRoleList AlterOptRoleList %type <defelt> CreateOptRoleElem AlterOptRoleElem %type <str> opt_type %type <str> foreign_server_version opt_foreign_server_version %type <str> opt_in_database %type <str> OptSchemaName %type <list> OptSchemaEltList %type <boolean> TriggerForSpec TriggerForType %type <ival> TriggerActionTime %type <list> TriggerEvents TriggerOneEvent %type <value> TriggerFuncArg %type <node> TriggerWhen %type <str> TransitionRelName %type <boolean> TransitionRowOrTable TransitionOldOrNew %type <node> TriggerTransition %type <list> event_trigger_when_list event_trigger_value_list %type <defelt> event_trigger_when_item %type <chr> enable_trigger %type <str> copy_file_name database_name access_method_clause access_method attr_name name cursor_name file_name index_name opt_index_name cluster_index_specification %type <list> func_name handler_name qual_Op qual_all_Op subquery_Op opt_class opt_inline_handler opt_validator validator_clause opt_collate %type <range> qualified_name insert_target OptConstrFromTable %type <str> all_Op MathOp %type <str> row_security_cmd RowSecurityDefaultForCmd %type <boolean> RowSecurityDefaultPermissive %type <node> RowSecurityOptionalWithCheck RowSecurityOptionalExpr %type <list> RowSecurityDefaultToRole RowSecurityOptionalToRole %type <str> iso_level opt_encoding %type <rolespec> grantee %type <list> grantee_list %type privilege %type <list> privileges privilege_list %type <privtarget> privilege_target %type <objwithargs> function_with_argtypes aggregate_with_argtypes operator_with_argtypes %type <list> function_with_argtypes_list aggregate_with_argtypes_list operator_with_argtypes_list %type <ival> defacl_privilege_target %type <defelt> DefACLOption %type <list> DefACLOptionList %type <ival> import_qualification_type %type <importqual> import_qualification %type <node> vacuum_relation %type <list> stmtblock stmtmulti OptTableElementList TableElementList OptInherit definition OptTypedTableElementList TypedTableElementList reloptions opt_reloptions OptWith distinct_clause opt_all_clause opt_definition func_args func_args_list func_args_with_defaults func_args_with_defaults_list aggr_args aggr_args_list func_as createfunc_opt_list alterfunc_opt_list old_aggr_definition old_aggr_list oper_argtypes RuleActionList RuleActionMulti opt_column_list columnList opt_name_list sort_clause opt_sort_clause sortby_list index_params opt_include opt_c_include index_including_params name_list role_list from_clause from_list opt_array_bounds qualified_name_list any_name any_name_list type_name_list any_operator expr_list attrs target_list opt_target_list insert_column_list set_target_list set_clause_list set_clause def_list operator_def_list indirection opt_indirection reloption_list group_clause TriggerFuncArgs select_limit opt_select_limit opclass_item_list opclass_drop_list opclass_purpose opt_opfamily transaction_mode_list_or_empty OptTableFuncElementList TableFuncElementList opt_type_modifiers prep_type_clause execute_param_clause using_clause returning_clause opt_enum_val_list enum_val_list table_func_column_list create_generic_options alter_generic_options relation_expr_list dostmt_opt_list transform_element_list transform_type_list TriggerTransitions TriggerReferencing publication_name_list vacuum_relation_list opt_vacuum_relation_list %type <list> group_by_list %type <node> group_by_item empty_grouping_set rollup_clause cube_clause %type <node> grouping_sets_clause %type <node> opt_publication_for_tables publication_for_tables %type <value> publication_name_item %type <list> opt_fdw_options fdw_options %type <defelt> fdw_option %type <range> OptTempTableName %type <into> into_clause create_as_target create_mv_target %type <defelt> createfunc_opt_item common_func_opt_item dostmt_opt_item %type <fun_param> func_arg func_arg_with_default table_func_column aggr_arg %type <fun_param_mode> arg_class %type <typnam> func_return func_type %type <boolean> opt_trusted opt_restart_seqs %type <ival> OptTemp %type <ival> OptNoLog %type <oncommit> OnCommitOption %type <ival> for_locking_strength %type <node> for_locking_item %type <list> for_locking_clause opt_for_locking_clause for_locking_items %type <list> locked_rels_list %type <boolean> all_or_distinct %type <node> join_outer join_qual %type <jtype> join_type %type <list> extract_list overlay_list position_list %type <list> substr_list trim_list %type <list> opt_interval interval_second %type <node> overlay_placing substr_from substr_for %type <boolean> opt_instead %type <boolean> opt_unique opt_concurrently opt_verbose opt_full %type <boolean> opt_freeze opt_analyze opt_default opt_recheck %type <defelt> opt_binary opt_oids copy_delimiter %type <boolean> copy_from opt_program %type <ival> opt_column event cursor_options opt_hold opt_set_data %type <objtype> drop_type_any_name drop_type_name drop_type_name_on_any_name comment_type_any_name comment_type_name security_label_type_any_name security_label_type_name %type <node> fetch_args limit_clause select_limit_value offset_clause select_offset_value select_fetch_first_value I_or_F_const %type <ival> row_or_rows first_or_next %type <list> OptSeqOptList SeqOptList OptParenthesizedSeqOptList %type <defelt> SeqOptElem %type <istmt> insert_rest %type <infer> opt_conf_expr %type <onconflict> opt_on_conflict %type <vsetstmt> generic_set set_rest set_rest_more generic_reset reset_rest SetResetClause FunctionSetResetClause %type <node> TableElement TypedTableElement ConstraintElem TableFuncElement %type <node> columnDef columnOptions %type <defelt> def_elem reloption_elem old_aggr_elem operator_def_elem %type <node> def_arg columnElem where_clause where_or_current_clause a_expr b_expr c_expr AexprConst indirection_el opt_slice_bound columnref in_expr having_clause func_table xmltable array_expr ExclusionWhereClause operator_def_arg %type <list> rowsfrom_item rowsfrom_list opt_col_def_list %type <boolean> opt_ordinality %type <list> ExclusionConstraintList ExclusionConstraintElem %type <list> func_arg_list %type <node> func_arg_expr %type <list> row explicit_row implicit_row type_list array_expr_list %type <node> case_expr case_arg when_clause case_default %type <list> when_clause_list %type <ival> sub_type %type <value> NumericOnly %type <list> NumericOnly_list %type alias_clause opt_alias_clause %type <list> func_alias_clause %type <sortby> sortby %type <ielem> index_elem %type <node> table_ref %type <jexpr> joined_table %type <range> relation_expr %type <range> relation_expr_opt_alias %type <node> tablesample_clause opt_repeatable_clause %type <target> target_el set_target insert_column_item %type <str> generic_option_name %type <node> generic_option_arg %type <defelt> generic_option_elem alter_generic_option_elem %type <list> generic_option_list alter_generic_option_list %type <str> explain_option_name %type <node> explain_option_arg %type <defelt> explain_option_elem %type <list> explain_option_list %type <ival> reindex_target_type reindex_target_multitable %type <ival> reindex_option_list reindex_option_elem %type <node> copy_generic_opt_arg copy_generic_opt_arg_list_item %type <defelt> copy_generic_opt_elem %type <list> copy_generic_opt_list copy_generic_opt_arg_list %type <list> copy_options %type <typnam> Typename SimpleTypename ConstTypename GenericType Numeric opt_float Character ConstCharacter CharacterWithLength CharacterWithoutLength ConstDatetime ConstInterval Bit ConstBit BitWithLength BitWithoutLength %type <str> character %type <str> extract_arg %type <boolean> opt_varying opt_timezone opt_no_inherit %type <ival> Iconst SignedIconst %type <str> Sconst comment_text notify_payload %type <str> RoleId opt_boolean_or_string %type <list> var_list %type <str> ColId ColLabel var_name type_function_name param_name %type <str> NonReservedWord NonReservedWord_or_Sconst %type <str> createdb_opt_name %type <node> var_value zone_value %type <rolespec> auth_ident RoleSpec opt_granted_by %type <keyword> unreserved_keyword type_func_name_keyword %type <keyword> col_name_keyword reserved_keyword %type <node> TableConstraint TableLikeClause %type <ival> TableLikeOptionList TableLikeOption %type <list> ColQualList %type <node> ColConstraint ColConstraintElem ConstraintAttr %type <ival> key_actions key_delete key_match key_update key_action %type <ival> ConstraintAttributeSpec ConstraintAttributeElem %type <str> ExistingIndex %type <list> constraints_set_list %type <boolean> constraints_set_mode %type <str> OptTableSpace OptConsTableSpace %type <rolespec> OptTableSpaceOwner %type <ival> opt_check_option %type <str> opt_provider security_label %type <target> xml_attribute_el %type <list> xml_attribute_list xml_attributes %type <node> xml_root_version opt_xml_root_standalone %type <node> xmlexists_argument %type <ival> document_or_content %type <boolean> xml_whitespace_option %type <list> xmltable_column_list xmltable_column_option_list %type <node> xmltable_column_el %type <defelt> xmltable_column_option_el %type <list> xml_namespace_list %type <target> xml_namespace_el %type <node> func_application func_expr_common_subexpr %type <node> func_expr func_expr_windowless %type <node> common_table_expr %type <with> with_clause opt_with_clause %type <list> cte_list %type <list> within_group_clause %type <node> filter_clause %type <list> window_clause window_definition_list opt_partition_clause %type <windef> window_definition over_clause window_specification opt_frame_clause frame_extent frame_bound %type <ival> opt_window_exclusion_clause %type <str> opt_existing_window_name %type <boolean> opt_if_not_exists %type <ival> generated_when override_kind %type <partspec> PartitionSpec OptPartitionSpec %type <str> part_strategy %type <partelem> part_elem %type <list> part_params %type <partboundspec> PartitionBoundSpec %type <node> partbound_datum PartitionRangeDatum %type <list> hash_partbound partbound_datum_list range_datum_list %type <defelt> hash_partbound_elem /* * Non-keyword token types. These are hard-wired into the "flex" lexer. * They must be listed first so that their numeric codes do not depend on * the set of keywords. PL/pgSQL depends on this so that it can share the * same lexer. If you add/change tokens here, fix PL/pgSQL to match! * 非关键字token类型. * 这些都被硬链接到"flex"的词法分析器中. * 必须首先列出这些token,这样他们的数字代码就不用依赖关键字集合了. * PL/pgsQL依赖于该集合以便可以共享相同的词法分析器. * 如果在这里添加/修改tokens,那么注意相应的修改PL/pgSQL. * * DOT_DOT is unused in the core SQL grammar, and so will always provoke * parse errors. It is needed by PL/pgSQL. * DOT_DOT在核心SQL语法中不会使用,因此通常会提示解析错误.用于PL/pgSQL. */ %token <str> IDENT FCONST SCONST BCONST XCONST Op %token <ival> ICONST PARAM %token TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER %token LESS_EQUALS GREATER_EQUALS NOT_EQUALS /* * If you want to make any keyword changes, update the keyword table in * src/include/parser/kwlist.h and add new keywords to the appropriate one * of the reserved-or-not-so-reserved keyword lists, below; search * this file for "Keyword category lists". * 如果希望修改关键字,更新src/include/parser/kwlist.h, * 同时在下面的关键字列表中在合适的位置添加新的关键字.可在文件中搜索"Keyword category lists" */ /* ordinary key words in alphabetical order */ //以字母顺序排列的普通关键字. %token <keyword> ABORT_P ABSOLUTE_P ACCESS ACTION ADD_P ADMIN AFTER AGGREGATE ALL ALSO ALTER ALWAYS ANAXXXE ANALYZE AND ANY ARRAY AS ASC ASSERTION ASSIGNMENT ASYMMETRIC AT ATTACH ATTRIBUTE AUTHORIZATION BACKWARD BEFORE BEGIN_P BETWEEN BIGINT BINARY BIT BOOLEAN_P BOTH BY CACHE CALL CALLED CASCADE CASCADED CASE CAST CATALOG_P CHAIN CHAR_P CHARACTER CHARACTERISTICS CHECK CHECKPOINT CLASS CLOSE CLUSTER COALESCE COLLATE COLLATION COLUMN COLUMNS COMMENT COMMENTS COMMIT COMMITTED CONCURRENTLY CONFIGURATION CONFLICT CONNECTION CONSTRAINT CONSTRAINTS CONTENT_P CONTINUE_P CONVERSION_P COPY COST CREATE CROSS CSV CUBE CURRENT_P CURRENT_CATALOG CURRENT_DATE CURRENT_ROLE CURRENT_SCHEMA CURRENT_TIME CURRENT_TIMESTAMP CURRENT_USER CURSOR CYCLE DATA_P DATABASE DAY_P DEALLOCATE DEC DECIMAL_P DECLARE DEFAULT DEFAULTS DEFERRABLE DEFERRED DEFINER DELETE_P DELIMITER DELIMITERS DEPENDS DESC DETACH DICTIONARY DISABLE_P DISCARD DISTINCT DO DOCUMENT_P DOMAIN_P DOUBLE_P DROP EACH ELSE ENABLE_P ENCODING ENCRYPTED END_P ENUM_P ESCAPE EVENT EXCEPT EXCLUDE EXCLUDING EXCLUSIVE EXECUTE EXISTS EXPLAIN EXTENSION EXTERNAL EXTRACT FALSE_P FAMILY FETCH FILTER FIRST_P FLOAT_P FOLLOWING FOR FORCE FOREIGN FORWARD FREEZE FROM FULL FUNCTION FUNCTIONS GENERATED GLOBAL GRANT GRANTED GREATEST GROUP_P GROUPING GROUPS HANDLER HAVING HEADER_P HOLD HOUR_P IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE INCLUDING INCREMENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION JOIN KEY LABEL LANGUAGE LARGE_P LAST_P LATERAL_P LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P MOVE NAME_P NAMES NATIONAL NATURAL NCHAR NEW NEXT NO NONE NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF NULLS_P NUMERIC OBJECT_P OF OFF OFFSET OIDS OLD ON ONLY OPERATOR OPTION OPTIONS OR ORDER ORDINALITY OTHERS OUT_P OUTER_P OVER OVERLAPS OVERLAY OVERRIDING OWNED OWNER PARALLEL PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POLICY POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY PRIOR PRIVILEGES PROCEDURAL PROCEDURE PROCEDURES PROGRAM PUBLICATION QUOTE RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFERENCING REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP ROUTINE ROUTINES ROW ROWS RULE SAVEPOINT SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES SERIALIZABLE SERVER SESSION SESSION_USER SET SETS SETOF SHARE SHOW SIMILAR SIMPLE SKIP SMALLINT SNAPSHOT SOME SQL_P STABLE STANDALONE_P START STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSCRIPTION SUBSTRING SYMMETRIC SYSID SYSTEM_P TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIES TIME TIMESTAMP TO TRAILING TRANSACTION TRANSFORM TREAT TRIGGER TRIM TRUE_P TRUNCATE TRUSTED TYPE_P TYPES_P UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED UNTIL UPDATE USER USING VACUUM VALID VALIDATE VALIDATOR VALUE_P VALUES VARCHAR VARIADIC VARYING VERBOSE VERSION_P VIEW VIEWS VOLATILE WHEN WHERE WHITESPACE_P WINDOW WITH WITHIN WITHOUT WORK WRAPPER WRITE XML_P XMLATTRIBUTES XMLCONCAT XMLELEMENT XMLEXISTS XMLFOREST XMLNAMESPACES XMLPARSE XMLPI XMLROOT XMLSERIALIZE XMLTABLE YEAR_P YES_P ZONE /* * The grammar thinks these are keywords, but they are not in the kwlist.h * list and so can never be entered directly. The filter in parser.c * creates these tokens when required (based on looking one token ahead). * 语法分析器认为存在关键字,但这些关键字没有在kwlist.h中列出,因此永远都不能直接进入. * parser.c中的过滤器在需要的时候创建这些tokens(基于提前查看一个token). * * NOT_LA exists so that productions such as NOT LIKE can be given the same * precedence as LIKE; otherwise they'd effectively have the same precedence * as NOT, at least with respect to their left-hand subexpression. * NULLS_LA and WITH_LA are needed to make the grammar LALR(1). * NOT_LA之所以存在以便诸如NOT LIKE这样的产生式可与LIKE具备同样的优先顺序. * 否则它们会与NOT的优先级一样,至少对于他们的左子表达式如此. * NULLS_LA和WITH_LA用于产生LALR(1)语法解析器. */ %token NOT_LA NULLS_LA WITH_LA /* Precedence: lowest to highest */ //优先级:从低到高 %nonassoc SET /* see relation_expr_opt_alias */ %left UNION EXCEPT %left INTERSECT %left OR %left AND %right NOT %nonassoc IS ISNULL NOTNULL /* IS sets precedence for IS NULL, etc */ %nonassoc '<' '>' '=' LESS_EQUALS GREATER_EQUALS NOT_EQUALS %nonassoc BETWEEN IN_P LIKE ILIKE SIMILAR NOT_LA //转义操作 %nonassoc ESCAPE /* ESCAPE must be just above LIKE/ILIKE/SIMILAR */ %left POSTFIXOP /* dummy for postfix Op rules */ /* * To support target_el without AS, we must give IDENT an explicit priority * between POSTFIXOP and Op. We can safely assign the same priority to * various unreserved keywords as needed to resolve ambiguities (this can't * have any bad effects since obviously the keywords will still behave the * same as if they weren't keywords). We need to do this: * for PARTITION, RANGE, ROWS, GROUPS to support opt_existing_window_name; * for RANGE, ROWS, GROUPS so that they can follow a_expr without creating * postfix-operator problems; * for GENERATED so that it can follow b_expr; * and for NULL so that it can follow b_expr in ColQualList without creating * postfix-operator problems. * 为了支持没有AS的target_el,必须在POSTFIXOP和Op之间明确的给IDENT一个显式的优先级. * 我们可以根据需要安全地为各种未保留的关键字分配相同的优先级,以解决歧义. * (这不会有什么不好的影响,因为显然的,关键字的行为与它们不是关键字是一样的). * 我们需要做的事情是: * 对于PARTITION, RANGE, ROWS, GROUPS,需要支持opt_existing_window_name; * 对于RANGE, ROWS, GROUPS,以便它们可以跟随a_expr而不会产生后缀操作符问题; * 对于GENERATED,可以跟随b_expr; * 对于NULL,可以在ColQualList中跟随b_expr而不会产生后缀操作符问题; * * To support CUBE and ROLLUP in GROUP BY without reserving them, we give them * an explicit priority lower than '(', so that a rule with CUBE '(' will shift * rather than reducing a conflicting rule that takes CUBE as a function name. * Using the same precedence as IDENT seems right for the reasons given above. * 在GROUP BY中支持CUBE/ROLLUP而无需保留它们,我们给予它们显示的优先级,要低于字符'(', * 这样存在CUBE '('的规则会进行状态转换而不是把CUBE视为函数名称而产生折叠冲突的规则. * 基于以上的理由,使用与IDENT相同的优先级似乎是正确的. * * The frame_bound productions UNBOUNDED PRECEDING and UNBOUNDED FOLLOWING * are even messier: since UNBOUNDED is an unreserved keyword (per spec!), * there is no principled way to distinguish these from the productions * . We hack this up by giving UNBOUNDED slightly * lower precedence than PRECEDING and FOLLOWING. At present this doesn't * appear to cause UNBOUNDED to be treated differently from other unreserved * keywords anywhere else in the grammar, but it's definitely risky. We can * blame any funny behavior of UNBOUNDED on the SQL standard, though. * frame_bound产生式UNBOUNDED PRECEDING和UNBOUNDED FOLLOWING更加混乱: * 因为UNBOUNDED是非保留关键字(per spec!),不存在明确的原则来区分产生式. * 通过给UNBOUNDED的优先级比PRECEDING和FOLLOWING更低优先级来解决此问题. * 到现在为止,看起来不会产生把UNBOUNDED与语法中其他任何地方的非保留关键字区别对待, * 但这肯定存在风险. * 不过,我们可以将UNBOUNDED的任何有趣行为归咎于SQL标准。 * */ //理想的情况下不应存在于IDENT相同的优先级. %nonassoc UNBOUNDED /* ideally should have same precedence as IDENT */ %nonassoc IDENT GENERATED NULL_P PARTITION RANGE ROWS GROUPS PRECEDING FOLLOWING CUBE ROLLUP //多字符组成的操作符和用户自定义操作符 %left Op OPERATOR /* multi-character ops and user-defined operators */ %left '+' '-' %left '*' '/' '%' %left '^' /* Unary Operators */ //一元运算符 %left AT /* sets precedence for AT TIME ZONE */ %left COLLATE %right UMINUS %left '[' ']' %left '(' ')' %left TYPECAST %left '.' /* * These might seem to be low-precedence, but actually they are not part * of the arithmetic hierarchy at all in their use as JOIN operators. * We make them high-precedence to support their use as function names. * They wouldn't be given a precedence at all, were it not that we need * left-associativity among the JOIN rules themselves. * 这些操作符看起来优先级比较低,但实际上在把它们作为连接操作符时, * 它们根本不是算术层次结构的一部分. * 提高它们的优先级,可以支持将它们用作函数名称. * 如果我们不需要连接规则本身的左结合性,它们根本就不会被授予优先级. */ %left JOIN CROSS LEFT FULL RIGHT INNER_P NATURAL /* kluge to keep xml_whitespace_option from causing shift/reduce conflicts */ //可防止xml_whitespace_option引起的转移/折叠冲突. %right PRESERVE STRIP_P ``` ### 三、参考资料 [Flex&Bison](http://web.iitd.ac.in/~sumeet/flex__bison.pdf)