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Support XMLTABLE query expression

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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
This commit is contained in:
Alvaro Herrera
2017-03-08 12:39:37 -03:00
parent 270d7dd8a5
commit fcec6caafa
52 changed files with 4606 additions and 50 deletions
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39
src/include/nodes/parsenodes.h
View File

@@ -554,6 +554,39 @@ typedef struct RangeFunction
* of function returning RECORD */
} RangeFunction;
/*
* RangeTableFunc - raw form of "table functions" such as XMLTABLE
*/
typedef struct RangeTableFunc
{
NodeTag type;
bool lateral; /* does it have LATERAL prefix? */
Node *docexpr; /* document expression */
Node *rowexpr; /* row generator expression */
List *namespaces; /* list of namespaces as ResTarget */
List *columns; /* list of RangeTableFuncCol */
Alias *alias; /* table alias & optional column aliases */
int location; /* token location, or -1 if unknown */
} RangeTableFunc;
/*
* RangeTableFuncCol - one column in a RangeTableFunc->columns
*
* If for_ordinality is true (FOR ORDINALITY), then the column is an int4
* column and the rest of the fields are ignored.
*/
typedef struct RangeTableFuncCol
{
NodeTag type;
char *colname; /* name of generated column */
TypeName *typeName; /* type of generated column */
bool for_ordinality; /* does it have FOR ORDINALITY? */
bool is_not_null; /* does it have NOT NULL? */
Node *colexpr; /* column filter expression */
Node *coldefexpr; /* column default value expression */
int location; /* token location, or -1 if unknown */
} RangeTableFuncCol;
/*
* RangeTableSample - TABLESAMPLE appearing in a raw FROM clause
*
@@ -871,6 +904,7 @@ typedef enum RTEKind
RTE_SUBQUERY, /* subquery in FROM */
RTE_JOIN, /* join */
RTE_FUNCTION, /* function in FROM */
RTE_TABLEFUNC, /* TableFunc(.., column list) */
RTE_VALUES, /* VALUES (<exprlist>), (<exprlist>), ... */
RTE_CTE /* common table expr (WITH list element) */
} RTEKind;
@@ -931,6 +965,11 @@ typedef struct RangeTblEntry
List *functions; /* list of RangeTblFunction nodes */
bool funcordinality; /* is this called WITH ORDINALITY? */
/*
* Fields valid for a TableFunc RTE (else NULL):
*/
TableFunc *tablefunc;
/*
* Fields valid for a values RTE (else NIL):
*/