parse_node.h

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/*-------------------------------------------------------------------------
 *
 * parse_node.h
 *      Internal definitions for parser
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/parser/parse_node.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PARSE_NODE_H
#define PARSE_NODE_H

#include "nodes/parsenodes.h"
#include "utils/queryenvironment.h"
#include "utils/relcache.h"


/* Forward references for some structs declared below */
typedef struct ParseState ParseState;
typedef struct ParseNamespaceItem ParseNamespaceItem;
typedef struct ParseNamespaceColumn ParseNamespaceColumn;

/*
 * Expression kinds distinguished by transformExpr().  Many of these are not
 * semantically distinct so far as expression transformation goes; rather,
 * we distinguish them so that context-specific error messages can be printed.
 *
 * Note: EXPR_KIND_OTHER is not used in the core code, but is left for use
 * by extension code that might need to call transformExpr().  The core code
 * will not enforce any context-driven restrictions on EXPR_KIND_OTHER
 * expressions, so the caller would have to check for sub-selects, aggregates,
 * window functions, SRFs, etc if those need to be disallowed.
 */
typedef enum ParseExprKind
{
    EXPR_KIND_NONE = 0,         /* "not in an expression" */
    EXPR_KIND_OTHER,            /* reserved for extensions */
    EXPR_KIND_JOIN_ON,          /* JOIN ON */
    EXPR_KIND_JOIN_USING,       /* JOIN USING */
    EXPR_KIND_FROM_SUBSELECT,   /* sub-SELECT in FROM clause */
    EXPR_KIND_FROM_FUNCTION,    /* function in FROM clause */
    EXPR_KIND_WHERE,            /* WHERE */
    EXPR_KIND_HAVING,           /* HAVING */
    EXPR_KIND_FILTER,           /* FILTER */
    EXPR_KIND_WINDOW_PARTITION, /* window definition PARTITION BY */
    EXPR_KIND_WINDOW_ORDER,     /* window definition ORDER BY */
    EXPR_KIND_WINDOW_FRAME_RANGE,   /* window frame clause with RANGE */
    EXPR_KIND_WINDOW_FRAME_ROWS,    /* window frame clause with ROWS */
    EXPR_KIND_WINDOW_FRAME_GROUPS,  /* window frame clause with GROUPS */
    EXPR_KIND_SELECT_TARGET,    /* SELECT target list item */
    EXPR_KIND_INSERT_TARGET,    /* INSERT target list item */
    EXPR_KIND_UPDATE_SOURCE,    /* UPDATE assignment source item */
    EXPR_KIND_UPDATE_TARGET,    /* UPDATE assignment target item */
    EXPR_KIND_GROUP_BY,         /* GROUP BY */
    EXPR_KIND_ORDER_BY,         /* ORDER BY */
    EXPR_KIND_DISTINCT_ON,      /* DISTINCT ON */
    EXPR_KIND_LIMIT,            /* LIMIT */
    EXPR_KIND_OFFSET,           /* OFFSET */
    EXPR_KIND_RETURNING,        /* RETURNING */
    EXPR_KIND_VALUES,           /* VALUES */
    EXPR_KIND_VALUES_SINGLE,    /* single-row VALUES (in INSERT only) */
    EXPR_KIND_CHECK_CONSTRAINT, /* CHECK constraint for a table */
    EXPR_KIND_DOMAIN_CHECK,     /* CHECK constraint for a domain */
    EXPR_KIND_COLUMN_DEFAULT,   /* default value for a table column */
    EXPR_KIND_FUNCTION_DEFAULT, /* default parameter value for function */
    EXPR_KIND_INDEX_EXPRESSION, /* index expression */
    EXPR_KIND_INDEX_PREDICATE,  /* index predicate */
    EXPR_KIND_ALTER_COL_TRANSFORM,  /* transform expr in ALTER COLUMN TYPE */
    EXPR_KIND_EXECUTE_PARAMETER,    /* parameter value in EXECUTE */
    EXPR_KIND_TRIGGER_WHEN,     /* WHEN condition in CREATE TRIGGER */
    EXPR_KIND_POLICY,           /* USING or WITH CHECK expr in policy */
    EXPR_KIND_PARTITION_BOUND,  /* partition bound expression */
    EXPR_KIND_PARTITION_EXPRESSION, /* PARTITION BY expression */
    EXPR_KIND_CALL_ARGUMENT,    /* procedure argument in CALL */
    EXPR_KIND_COPY_WHERE,       /* WHERE condition in COPY FROM */
    EXPR_KIND_GENERATED_COLUMN, /* generation expression for a column */
} ParseExprKind;


/*
 * Function signatures for parser hooks
 */
typedef Node *(*PreParseColumnRefHook) (ParseState *pstate, ColumnRef *cref);
typedef Node *(*PostParseColumnRefHook) (ParseState *pstate, ColumnRef *cref, Node *var);
typedef Node *(*ParseParamRefHook) (ParseState *pstate, ParamRef *pref);
typedef Node *(*CoerceParamHook) (ParseState *pstate, Param *param,
                                  Oid targetTypeId, int32 targetTypeMod,
                                  int location);


/*
 * State information used during parse analysis
 *
 * parentParseState: NULL in a top-level ParseState.  When parsing a subquery,
 * links to current parse state of outer query.
 *
 * p_sourcetext: source string that generated the raw parsetree being
 * analyzed, or NULL if not available.  (The string is used only to
 * generate cursor positions in error messages: we need it to convert
 * byte-wise locations in parse structures to character-wise cursor
 * positions.)
 *
 * p_rtable: list of RTEs that will become the rangetable of the query.
 * Note that neither relname nor refname of these entries are necessarily
 * unique; searching the rtable by name is a bad idea.
 *
 * p_joinexprs: list of JoinExpr nodes associated with p_rtable entries.
 * This is one-for-one with p_rtable, but contains NULLs for non-join
 * RTEs, and may be shorter than p_rtable if the last RTE(s) aren't joins.
 *
 * p_joinlist: list of join items (RangeTblRef and JoinExpr nodes) that
 * will become the fromlist of the query's top-level FromExpr node.
 *
 * p_namespace: list of ParseNamespaceItems that represents the current
 * namespace for table and column lookup.  (The RTEs listed here may be just
 * a subset of the whole rtable.  See ParseNamespaceItem comments below.)
 *
 * p_lateral_active: true if we are currently parsing a LATERAL subexpression
 * of this parse level.  This makes p_lateral_only namespace items visible,
 * whereas they are not visible when p_lateral_active is FALSE.
 *
 * p_ctenamespace: list of CommonTableExprs (WITH items) that are visible
 * at the moment.  This is entirely different from p_namespace because a CTE
 * is not an RTE, rather "visibility" means you could make an RTE from it.
 *
 * p_future_ctes: list of CommonTableExprs (WITH items) that are not yet
 * visible due to scope rules.  This is used to help improve error messages.
 *
 * p_parent_cte: CommonTableExpr that immediately contains the current query,
 * if any.
 *
 * p_target_relation: target relation, if query is INSERT, UPDATE, or DELETE.
 *
 * p_target_nsitem: target relation's ParseNamespaceItem.
 *
 * p_is_insert: true to process assignment expressions like INSERT, false
 * to process them like UPDATE.  (Note this can change intra-statement, for
 * cases like INSERT ON CONFLICT UPDATE.)
 *
 * p_windowdefs: list of WindowDefs representing WINDOW and OVER clauses.
 * We collect these while transforming expressions and then transform them
 * afterwards (so that any resjunk tlist items needed for the sort/group
 * clauses end up at the end of the query tlist).  A WindowDef's location in
 * this list, counting from 1, is the winref number to use to reference it.
 *
 * p_expr_kind: kind of expression we're currently parsing, as per enum above;
 * EXPR_KIND_NONE when not in an expression.
 *
 * p_next_resno: next TargetEntry.resno to assign, starting from 1.
 *
 * p_multiassign_exprs: partially-processed MultiAssignRef source expressions.
 *
 * p_locking_clause: query's FOR UPDATE/FOR SHARE clause, if any.
 *
 * p_locked_from_parent: true if parent query level applies FOR UPDATE/SHARE
 * to this subquery as a whole.
 *
 * p_resolve_unknowns: resolve unknown-type SELECT output columns as type TEXT
 * (this is true by default).
 *
 * p_hasAggs, p_hasWindowFuncs, etc: true if we've found any of the indicated
 * constructs in the query.
 *
 * p_last_srf: the set-returning FuncExpr or OpExpr most recently found in
 * the query, or NULL if none.
 *
 * p_pre_columnref_hook, etc: optional parser hook functions for modifying the
 * interpretation of ColumnRefs and ParamRefs.
 *
 * p_ref_hook_state: passthrough state for the parser hook functions.
 */
struct ParseState
{
    ParseState *parentParseState;   /* stack link */
    const char *p_sourcetext;   /* source text, or NULL if not available */
    List       *p_rtable;       /* range table so far */
    List       *p_joinexprs;    /* JoinExprs for RTE_JOIN p_rtable entries */
    List       *p_joinlist;     /* join items so far (will become FromExpr
                                 * node's fromlist) */
    List       *p_namespace;    /* currently-referenceable RTEs (List of
                                 * ParseNamespaceItem) */
    bool        p_lateral_active;   /* p_lateral_only items visible? */
    List       *p_ctenamespace; /* current namespace for common table exprs */
    List       *p_future_ctes;  /* common table exprs not yet in namespace */
    CommonTableExpr *p_parent_cte;  /* this query's containing CTE */
    Relation    p_target_relation;  /* INSERT/UPDATE/DELETE target rel */
    ParseNamespaceItem *p_target_nsitem;    /* target rel's NSItem, or NULL */
    bool        p_is_insert;    /* process assignment like INSERT not UPDATE */
    List       *p_windowdefs;   /* raw representations of window clauses */
    ParseExprKind p_expr_kind;  /* what kind of expression we're parsing */
    int         p_next_resno;   /* next targetlist resno to assign */
    List       *p_multiassign_exprs;    /* junk tlist entries for multiassign */
    List       *p_locking_clause;   /* raw FOR UPDATE/FOR SHARE info */
    bool        p_locked_from_parent;   /* parent has marked this subquery
                                         * with FOR UPDATE/FOR SHARE */
    bool        p_resolve_unknowns; /* resolve unknown-type SELECT outputs as
                                     * type text */

    QueryEnvironment *p_queryEnv;   /* curr env, incl refs to enclosing env */

    /* Flags telling about things found in the query: */
    bool        p_hasAggs;
    bool        p_hasWindowFuncs;
    bool        p_hasTargetSRFs;
    bool        p_hasSubLinks;
    bool        p_hasModifyingCTE;

    Node       *p_last_srf;     /* most recent set-returning func/op found */

    /*
     * Optional hook functions for parser callbacks.  These are null unless
     * set up by the caller of make_parsestate.
     */
    PreParseColumnRefHook p_pre_columnref_hook;
    PostParseColumnRefHook p_post_columnref_hook;
    ParseParamRefHook p_paramref_hook;
    CoerceParamHook p_coerce_param_hook;
    void       *p_ref_hook_state;   /* common passthrough link for above */
};

/*
 * An element of a namespace list.
 *
 * The p_nscolumns array contains info showing how to construct Vars
 * referencing corresponding elements of the RTE's colnames list.
 *
 * Namespace items with p_rel_visible set define which RTEs are accessible by
 * qualified names, while those with p_cols_visible set define which RTEs are
 * accessible by unqualified names.  These sets are different because a JOIN
 * without an alias does not hide the contained tables (so they must be
 * visible for qualified references) but it does hide their columns
 * (unqualified references to the columns refer to the JOIN, not the member
 * tables, so we must not complain that such a reference is ambiguous).
 * Various special RTEs such as NEW/OLD for rules may also appear with only
 * one flag set.
 *
 * While processing the FROM clause, namespace items may appear with
 * p_lateral_only set, meaning they are visible only to LATERAL
 * subexpressions.  (The pstate's p_lateral_active flag tells whether we are
 * inside such a subexpression at the moment.)  If p_lateral_ok is not set,
 * it's an error to actually use such a namespace item.  One might think it
 * would be better to just exclude such items from visibility, but the wording
 * of SQL:2008 requires us to do it this way.  We also use p_lateral_ok to
 * forbid LATERAL references to an UPDATE/DELETE target table.
 *
 * At no time should a namespace list contain two entries that conflict
 * according to the rules in checkNameSpaceConflicts; but note that those
 * are more complicated than "must have different alias names", so in practice
 * code searching a namespace list has to check for ambiguous references.
 */
struct ParseNamespaceItem
{
    RangeTblEntry *p_rte;       /* The relation's rangetable entry */
    int         p_rtindex;      /* The relation's index in the rangetable */
    /* array of same length as p_rte->eref->colnames: */
    ParseNamespaceColumn *p_nscolumns;  /* per-column data */
    bool        p_rel_visible;  /* Relation name is visible? */
    bool        p_cols_visible; /* Column names visible as unqualified refs? */
    bool        p_lateral_only; /* Is only visible to LATERAL expressions? */
    bool        p_lateral_ok;   /* If so, does join type allow use? */
};

/*
 * Data about one column of a ParseNamespaceItem.
 *
 * We track the info needed to construct a Var referencing the column
 * (but only for user-defined columns; system column references and
 * whole-row references are handled separately).
 *
 * p_varno and p_varattno identify the semantic referent, which is a
 * base-relation column unless the reference is to a join USING column that
 * isn't semantically equivalent to either join input column (because it is a
 * FULL join or the input column requires a type coercion).  In those cases
 * p_varno and p_varattno refer to the JOIN RTE.
 *
 * p_varnosyn and p_varattnosyn are either identical to p_varno/p_varattno,
 * or they specify the column's position in an aliased JOIN RTE that hides
 * the semantic referent RTE's refname.  (That could be either the JOIN RTE
 * in which this ParseNamespaceColumn entry exists, or some lower join level.)
 *
 * If an RTE contains a dropped column, its ParseNamespaceColumn struct
 * is all-zeroes.  (Conventionally, test for p_varno == 0 to detect this.)
 */
struct ParseNamespaceColumn
{
    Index       p_varno;        /* rangetable index */
    AttrNumber  p_varattno;     /* attribute number of the column */
    Oid         p_vartype;      /* pg_type OID */
    int32       p_vartypmod;    /* type modifier value */
    Oid         p_varcollid;    /* OID of collation, or InvalidOid */
    Index       p_varnosyn;     /* rangetable index of syntactic referent */
    AttrNumber  p_varattnosyn;  /* attribute number of syntactic referent */
};

/* Support for parser_errposition_callback function */
typedef struct ParseCallbackState
{
    ParseState *pstate;
    int         location;
    ErrorContextCallback errcallback;
} ParseCallbackState;


extern ParseState *make_parsestate(ParseState *parentParseState);
extern void free_parsestate(ParseState *pstate);
extern int  parser_errposition(ParseState *pstate, int location);

extern void setup_parser_errposition_callback(ParseCallbackState *pcbstate,
                                              ParseState *pstate, int location);
extern void cancel_parser_errposition_callback(ParseCallbackState *pcbstate);

extern void transformContainerType(Oid *containerType, int32 *containerTypmod);

extern SubscriptingRef *transformContainerSubscripts(ParseState *pstate,
                                                     Node *containerBase,
                                                     Oid containerType,
                                                     int32 containerTypMod,
                                                     List *indirection,
                                                     bool isAssignment);

extern Const *make_const(ParseState *pstate, Value *value, int location);

#endif                          /* PARSE_NODE_H */