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XMLTABLE is defined by the SQL/XML standard as a feature that allows turning XML-formatted data into relational form, so that it can be used as a <table primary> in the FROM clause of a query. This new construct provides significant simplicity and performance benefit for XML data processing; what in a client-side custom implementation was reported to take 20 minutes can be executed in 400ms using XMLTABLE. (The same functionality was said to take 10 seconds using nested PostgreSQL XPath function calls, and 5 seconds using XMLReader under PL/Python). The implemented syntax deviates slightly from what the standard requires. First, the standard indicates that the PASSING clause is optional and that multiple XML input documents may be given to it; we make it mandatory and accept a single document only. Second, we don't currently support a default namespace to be specified. This implementation relies on a new executor node based on a hardcoded method table. (Because the grammar is fixed, there is no extensibility in the current approach; further constructs can be implemented on top of this such as JSON_TABLE, but they require changes to core code.) Author: Pavel Stehule, Álvaro Herrera Extensively reviewed by: Craig Ringer Discussion: https://postgr.es/m/CAFj8pRAgfzMD-LoSmnMGybD0WsEznLHWap8DO79+-GTRAPR4qA@mail.gmail.com
95 lines
3.2 KiB
C
95 lines
3.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* parse_coerce.h
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* Routines for type coercion.
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*
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*
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* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/parser/parse_coerce.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PARSE_COERCE_H
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#define PARSE_COERCE_H
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#include "parser/parse_node.h"
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/* Type categories (see TYPCATEGORY_xxx symbols in catalog/pg_type.h) */
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typedef char TYPCATEGORY;
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/* Result codes for find_coercion_pathway */
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typedef enum CoercionPathType
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{
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COERCION_PATH_NONE, /* failed to find any coercion pathway */
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COERCION_PATH_FUNC, /* apply the specified coercion function */
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COERCION_PATH_RELABELTYPE, /* binary-compatible cast, no function */
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COERCION_PATH_ARRAYCOERCE, /* need an ArrayCoerceExpr node */
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COERCION_PATH_COERCEVIAIO /* need a CoerceViaIO node */
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} CoercionPathType;
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extern bool IsBinaryCoercible(Oid srctype, Oid targettype);
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extern bool IsPreferredType(TYPCATEGORY category, Oid type);
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extern TYPCATEGORY TypeCategory(Oid type);
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extern Node *coerce_to_target_type(ParseState *pstate,
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Node *expr, Oid exprtype,
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Oid targettype, int32 targettypmod,
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CoercionContext ccontext,
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CoercionForm cformat,
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int location);
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extern bool can_coerce_type(int nargs, Oid *input_typeids, Oid *target_typeids,
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CoercionContext ccontext);
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extern Node *coerce_type(ParseState *pstate, Node *node,
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Oid inputTypeId, Oid targetTypeId, int32 targetTypeMod,
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CoercionContext ccontext, CoercionForm cformat, int location);
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extern Node *coerce_to_domain(Node *arg, Oid baseTypeId, int32 baseTypeMod,
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Oid typeId,
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CoercionForm cformat, int location,
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bool hideInputCoercion,
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bool lengthCoercionDone);
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extern Node *coerce_to_boolean(ParseState *pstate, Node *node,
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const char *constructName);
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extern Node *coerce_to_specific_type(ParseState *pstate, Node *node,
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Oid targetTypeId,
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const char *constructName);
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extern Node *coerce_to_specific_type_typmod(ParseState *pstate, Node *node,
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Oid targetTypeId, int32 targetTypmod,
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const char *constructName);
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extern int parser_coercion_errposition(ParseState *pstate,
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int coerce_location,
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Node *input_expr);
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extern Oid select_common_type(ParseState *pstate, List *exprs,
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const char *context, Node **which_expr);
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extern Node *coerce_to_common_type(ParseState *pstate, Node *node,
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Oid targetTypeId,
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const char *context);
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extern bool check_generic_type_consistency(Oid *actual_arg_types,
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Oid *declared_arg_types,
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int nargs);
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extern Oid enforce_generic_type_consistency(Oid *actual_arg_types,
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Oid *declared_arg_types,
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int nargs,
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Oid rettype,
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bool allow_poly);
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extern Oid resolve_generic_type(Oid declared_type,
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Oid context_actual_type,
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Oid context_declared_type);
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extern CoercionPathType find_coercion_pathway(Oid targetTypeId,
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Oid sourceTypeId,
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CoercionContext ccontext,
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Oid *funcid);
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extern CoercionPathType find_typmod_coercion_function(Oid typeId,
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Oid *funcid);
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#endif /* PARSE_COERCE_H */
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