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本篇內容介紹了“PostgreSQL怎么實現用戶自定義”的有關知識，在實際案例的操作過程中，不少人都會遇到這樣的困境，接下來就讓小編帶領大家學習一下如何處理這些情況吧！希望大家仔細閱讀，能夠學有所成！
Bison輸入文件的組成:
%{
Declarations
%}
Definitions
%%
Productions
%%
User subroutines用戶自定義例程會原封不動的拷貝到gram.c文件中,詳細請參考gram.c文件.
下面是gram.y用戶自定義部分的源碼
/*
* The signature of this function is required by bison. However, we
* ignore the passed yylloc and instead use the last token position
* available from the scanner.
*/
static void
base_yyerror(YYLTYPE *yylloc, core_yyscan_t yyscanner, const char *msg)
{
parser_yyerror(msg);
}
static RawStmt *
makeRawStmt(Node *stmt, int stmt_location)
{
RawStmt *rs = makeNode(RawStmt);
rs->stmt = stmt;
rs->stmt_location = stmt_location;
rs->stmt_len = 0; /* might get changed later */
return rs;
}
/* Adjust a RawStmt to reflect that it doesn't run to the end of the string */
static void
updateRawStmtEnd(RawStmt *rs, int end_location)
{
/*
* If we already set the length, don't change it. This is for situations
* like "select foo ;; select bar" where the same statement will be last
* in the string for more than one semicolon.
*/
if (rs->stmt_len > 0)
return;
/* OK, update length of RawStmt */
rs->stmt_len = end_location - rs->stmt_location;
}
static Node *
makeColumnRef(char *colname, List *indirection,
int location, core_yyscan_t yyscanner)
{
/*
* Generate a ColumnRef node, with an A_Indirection node added if there
* is any subscripting in the specified indirection list. However,
* any field selection at the start of the indirection list must be
* transposed into the "fields" part of the ColumnRef node.
*/
ColumnRef *c = makeNode(ColumnRef);
int nfields = 0;
ListCell *l;
c->location = location;
foreach(l, indirection)
{
if (IsA(lfirst(l), A_Indices))
{
A_Indirection *i = makeNode(A_Indirection);
if (nfields == 0)
{
/* easy case - all indirection goes to A_Indirection */
c->fields = list_make1(makeString(colname));
i->indirection = check_indirection(indirection, yyscanner);
}
else
{
/* got to split the list in two */
i->indirection = check_indirection(list_copy_tail(indirection,
nfields),
yyscanner);
indirection = list_truncate(indirection, nfields);
c->fields = lcons(makeString(colname), indirection);
}
i->arg = (Node *) c;
return (Node *) i;
}
else if (IsA(lfirst(l), A_Star))
{
/* We only allow '*' at the end of a ColumnRef */
if (lnext(l) != NULL)
parser_yyerror("improper use of \"*\"");
}
nfields++;
}
/* No subscripting, so all indirection gets added to field list */
c->fields = lcons(makeString(colname), indirection);
return (Node *) c;
}
static Node *
makeTypeCast(Node *arg, TypeName *typename, int location)
{
TypeCast *n = makeNode(TypeCast);
n->arg = arg;
n->typeName = typename;
n->location = location;
return (Node *) n;
}
static Node *
makeStringConst(char *str, int location)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_String;
n->val.val.str = str;
n->location = location;
return (Node *)n;
}
static Node *
makeStringConstCast(char *str, int location, TypeName *typename)
{
Node *s = makeStringConst(str, location);
return makeTypeCast(s, typename, -1);
}
static Node *
makeIntConst(int val, int location)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Integer;
n->val.val.ival = val;
n->location = location;
return (Node *)n;
}
static Node *
makeFloatConst(char *str, int location)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Float;
n->val.val.str = str;
n->location = location;
return (Node *)n;
}
static Node *
makeBitStringConst(char *str, int location)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_BitString;
n->val.val.str = str;
n->location = location;
return (Node *)n;
}
static Node *
makeNullAConst(int location)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_Null;
n->location = location;
return (Node *)n;
}
static Node *
makeAConst(Value *v, int location)
{
Node *n;
switch (v->type)
{
case T_Float:
n = makeFloatConst(v->val.str, location);
break;
case T_Integer:
n = makeIntConst(v->val.ival, location);
break;
case T_String:
default:
n = makeStringConst(v->val.str, location);
break;
}
return n;
}
/* makeBoolAConst()
* Create an A_Const string node and put it inside a boolean cast.
*/
static Node *
makeBoolAConst(bool state, int location)
{
A_Const *n = makeNode(A_Const);
n->val.type = T_String;
n->val.val.str = (state ? "t" : "f");
n->location = location;
return makeTypeCast((Node *)n, SystemTypeName("bool"), -1);
}
/* makeRoleSpec
* Create a RoleSpec with the given type
*/
static RoleSpec *
makeRoleSpec(RoleSpecType type, int location)
{
RoleSpec *spec = makeNode(RoleSpec);
spec->roletype = type;
spec->location = location;
return spec;
}
/* check_qualified_name --- check the result of qualified_name production
*
* It's easiest to let the grammar production for qualified_name allow
* subscripts and '*', which we then must reject here.
*/
static void
check_qualified_name(List *names, core_yyscan_t yyscanner)
{
ListCell *i;
foreach(i, names)
{
if (!IsA(lfirst(i), String))
parser_yyerror("syntax error");
}
}
/* check_func_name --- check the result of func_name production
*
* It's easiest to let the grammar production for func_name allow subscripts
* and '*', which we then must reject here.
*/
static List *
check_func_name(List *names, core_yyscan_t yyscanner)
{
ListCell *i;
foreach(i, names)
{
if (!IsA(lfirst(i), String))
parser_yyerror("syntax error");
}
return names;
}
/* check_indirection --- check the result of indirection production
*
* We only allow '*' at the end of the list, but it's hard to enforce that
* in the grammar, so do it here.
*/
static List *
check_indirection(List *indirection, core_yyscan_t yyscanner)
{
ListCell *l;
foreach(l, indirection)
{
if (IsA(lfirst(l), A_Star))
{
if (lnext(l) != NULL)
parser_yyerror("improper use of \"*\"");
}
}
return indirection;
}
/* extractArgTypes()
* Given a list of FunctionParameter nodes, extract a list of just the
* argument types (TypeNames) for input parameters only. This is what
* is needed to look up an existing function, which is what is wanted by
* the productions that use this call.
*/
static List *
extractArgTypes(List *parameters)
{
List *result = NIL;
ListCell *i;
foreach(i, parameters)
{
FunctionParameter *p = (FunctionParameter *) lfirst(i);
if (p->mode != FUNC_PARAM_OUT && p->mode != FUNC_PARAM_TABLE)
result = lappend(result, p->argType);
}
return result;
}
/* extractAggrArgTypes()
* As above, but work from the output of the aggr_args production.
*/
static List *
extractAggrArgTypes(List *aggrargs)
{
Assert(list_length(aggrargs) == 2);
return extractArgTypes((List *) linitial(aggrargs));
}
/* makeOrderedSetArgs()
* Build the result of the aggr_args production (which see the comments for).
* This handles only the case where both given lists are nonempty, so that
* we have to deal with multiple VARIADIC arguments.
*/
static List *
makeOrderedSetArgs(List *directargs, List *orderedargs,
core_yyscan_t yyscanner)
{
FunctionParameter *lastd = (FunctionParameter *) llast(directargs);
int ndirectargs;
/* No restriction unless last direct arg is VARIADIC */
if (lastd->mode == FUNC_PARAM_VARIADIC)
{
FunctionParameter *firsto = (FunctionParameter *) linitial(orderedargs);
/*
* We ignore the names, though the aggr_arg production allows them;
* it doesn't allow default values, so those need not be checked.
*/
if (list_length(orderedargs) != 1 ||
firsto->mode != FUNC_PARAM_VARIADIC ||
!equal(lastd->argType, firsto->argType))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("an ordered-set aggregate with a VARIADIC direct argument must have one VARIADIC aggregated argument of the same data type"),
parser_errposition(exprLocation((Node *) firsto))));
/* OK, drop the duplicate VARIADIC argument from the internal form */
orderedargs = NIL;
}
/* don't merge into the next line, as list_concat changes directargs */
ndirectargs = list_length(directargs);
return list_make2(list_concat(directargs, orderedargs),
makeInteger(ndirectargs));
}
/* insertSelectOptions()
* Insert ORDER BY, etc into an already-constructed SelectStmt.
*
* This routine is just to avoid duplicating code in SelectStmt productions.
*/
static void
insertSelectOptions(SelectStmt *stmt,
List *sortClause, List *lockingClause,
Node *limitOffset, Node *limitCount,
WithClause *withClause,
core_yyscan_t yyscanner)
{
Assert(IsA(stmt, SelectStmt));
/*
* Tests here are to reject constructs like
* (SELECT foo ORDER BY bar) ORDER BY baz
*/
if (sortClause)
{
if (stmt->sortClause)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple ORDER BY clauses not allowed"),
parser_errposition(exprLocation((Node *) sortClause))));
stmt->sortClause = sortClause;
}
/* We can handle multiple locking clauses, though */
stmt->lockingClause = list_concat(stmt->lockingClause, lockingClause);
if (limitOffset)
{
if (stmt->limitOffset)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple OFFSET clauses not allowed"),
parser_errposition(exprLocation(limitOffset))));
stmt->limitOffset = limitOffset;
}
if (limitCount)
{
if (stmt->limitCount)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple LIMIT clauses not allowed"),
parser_errposition(exprLocation(limitCount))));
stmt->limitCount = limitCount;
}
if (withClause)
{
if (stmt->withClause)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple WITH clauses not allowed"),
parser_errposition(exprLocation((Node *) withClause))));
stmt->withClause = withClause;
}
}
static Node *
makeSetOp(SetOperation op, bool all, Node *larg, Node *rarg)
{
SelectStmt *n = makeNode(SelectStmt);
n->op = op;
n->all = all;
n->larg = (SelectStmt *) larg;
n->rarg = (SelectStmt *) rarg;
return (Node *) n;
}
/* SystemFuncName()
* Build a properly-qualified reference to a built-in function.
*/
List *
SystemFuncName(char *name)
{
return list_make2(makeString("pg_catalog"), makeString(name));
}
/* SystemTypeName()
* Build a properly-qualified reference to a built-in type.
*
* typmod is defaulted, but may be changed afterwards by caller.
* Likewise for the location.
*/
TypeName *
SystemTypeName(char *name)
{
return makeTypeNameFromNameList(list_make2(makeString("pg_catalog"),
makeString(name)));
}
/* doNegate()
* Handle negation of a numeric constant.
*
* Formerly, we did this here because the optimizer couldn't cope with
* indexquals that looked like "var = -4" --- it wants "var = const"
* and a unary minus operator applied to a constant didn't qualify.
* As of Postgres 7.0, that problem doesn't exist anymore because there
* is a constant-subexpression simplifier in the optimizer. However,
* there's still a good reason for doing this here, which is that we can
* postpone committing to a particular internal representation for simple
* negative constants. It's better to leave "-123.456" in string form
* until we know what the desired type is.
*/
static Node *
doNegate(Node *n, int location)
{
if (IsA(n, A_Const))
{
A_Const *con = (A_Const *)n;
/* report the constant's location as that of the '-' sign */
con->location = location;
if (con->val.type == T_Integer)
{
con->val.val.ival = -con->val.val.ival;
return n;
}
if (con->val.type == T_Float)
{
doNegateFloat(&con->val);
return n;
}
}
return (Node *) makeSimpleA_Expr(AEXPR_OP, "-", NULL, n, location);
}
static void
doNegateFloat(Value *v)
{
char *oldval = v->val.str;
Assert(IsA(v, Float));
if (*oldval == '+')
oldval++;
if (*oldval == '-')
v->val.str = oldval+1; /* just strip the '-' */
else
v->val.str = psprintf("-%s", oldval);
}
static Node *
makeAndExpr(Node *lexpr, Node *rexpr, int location)
{
Node *lexp = lexpr;
/* Look through AEXPR_PAREN nodes so they don't affect flattening */
while (IsA(lexp, A_Expr) &&
((A_Expr *) lexp)->kind == AEXPR_PAREN)
lexp = ((A_Expr *) lexp)->lexpr;
/* Flatten "a AND b AND c ..." to a single BoolExpr on sight */
if (IsA(lexp, BoolExpr))
{
BoolExpr *blexpr = (BoolExpr *) lexp;
if (blexpr->boolop == AND_EXPR)
{
blexpr->args = lappend(blexpr->args, rexpr);
return (Node *) blexpr;
}
}
return (Node *) makeBoolExpr(AND_EXPR, list_make2(lexpr, rexpr), location);
}
static Node *
makeOrExpr(Node *lexpr, Node *rexpr, int location)
{
Node *lexp = lexpr;
/* Look through AEXPR_PAREN nodes so they don't affect flattening */
while (IsA(lexp, A_Expr) &&
((A_Expr *) lexp)->kind == AEXPR_PAREN)
lexp = ((A_Expr *) lexp)->lexpr;
/* Flatten "a OR b OR c ..." to a single BoolExpr on sight */
if (IsA(lexp, BoolExpr))
{
BoolExpr *blexpr = (BoolExpr *) lexp;
if (blexpr->boolop == OR_EXPR)
{
blexpr->args = lappend(blexpr->args, rexpr);
return (Node *) blexpr;
}
}
return (Node *) makeBoolExpr(OR_EXPR, list_make2(lexpr, rexpr), location);
}
static Node *
makeNotExpr(Node *expr, int location)
{
return (Node *) makeBoolExpr(NOT_EXPR, list_make1(expr), location);
}
static Node *
makeAArrayExpr(List *elements, int location)
{
A_ArrayExpr *n = makeNode(A_ArrayExpr);
n->elements = elements;
n->location = location;
return (Node *) n;
}
static Node *
makeSQLValueFunction(SQLValueFunctionOp op, int32 typmod, int location)
{
SQLValueFunction *svf = makeNode(SQLValueFunction);
svf->op = op;
/* svf->type will be filled during parse anaXXXis */
svf->typmod = typmod;
svf->location = location;
return (Node *) svf;
}
static Node *
makeXmlExpr(XmlExprOp op, char *name, List *named_args, List *args,
int location)
{
XmlExpr *x = makeNode(XmlExpr);
x->op = op;
x->name = name;
/*
* named_args is a list of ResTarget; it'll be split apart into separate
* expression and name lists in transformXmlExpr().
*/
x->named_args = named_args;
x->arg_names = NIL;
x->args = args;
/* xmloption, if relevant, must be filled in by caller */
/* type and typmod will be filled in during parse anaXXXis */
x->type = InvalidOid; /* marks the node as not analyzed */
x->location = location;
return (Node *) x;
}
/*
* Merge the input and output parameters of a table function.
*/
static List *
mergeTableFuncParameters(List *func_args, List *columns)
{
ListCell *lc;
/* Explicit OUT and INOUT parameters shouldn't be used in this syntax */
foreach(lc, func_args)
{
FunctionParameter *p = (FunctionParameter *) lfirst(lc);
if (p->mode != FUNC_PARAM_IN && p->mode != FUNC_PARAM_VARIADIC)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("OUT and INOUT arguments aren't allowed in TABLE functions")));
}
return list_concat(func_args, columns);
}
/*
* Determine return type of a TABLE function. A single result column
* returns setof that column's type; otherwise return setof record.
*/
static TypeName *
TableFuncTypeName(List *columns)
{
TypeName *result;
if (list_length(columns) == 1)
{
FunctionParameter *p = (FunctionParameter *) linitial(columns);
result = copyObject(p->argType);
}
else
result = SystemTypeName("record");
result->setof = true;
return result;
}
/*
* Convert a list of (dotted) names to a RangeVar (like
* makeRangeVarFromNameList, but with position support). The
* "AnyName" refers to the any_name production in the grammar.
*/
static RangeVar *
makeRangeVarFromAnyName(List *names, int position, core_yyscan_t yyscanner)
{
RangeVar *r = makeNode(RangeVar);
switch (list_length(names))
{
case 1:
r->catalogname = NULL;
r->schemaname = NULL;
r->relname = strVal(linitial(names));
break;
case 2:
r->catalogname = NULL;
r->schemaname = strVal(linitial(names));
r->relname = strVal(lsecond(names));
break;
case 3:
r->catalogname = strVal(linitial(names));
r->schemaname = strVal(lsecond(names));
r->relname = strVal(lthird(names));
break;
default:
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("improper qualified name (too many dotted names): %s",
NameListToString(names)),
parser_errposition(position)));
break;
}
r->relpersistence = RELPERSISTENCE_PERMANENT;
r->location = position;
return r;
}
/* Separate Constraint nodes from COLLATE clauses in a ColQualList */
static void
SplitColQualList(List *qualList,
List **constraintList, CollateClause **collClause,
core_yyscan_t yyscanner)
{
ListCell *cell;
ListCell *prev;
ListCell *next;
*collClause = NULL;
prev = NULL;
for (cell = list_head(qualList); cell; cell = next)
{
Node *n = (Node *) lfirst(cell);
next = lnext(cell);
if (IsA(n, Constraint))
{
/* keep it in list */
prev = cell;
continue;
}
if (IsA(n, CollateClause))
{
CollateClause *c = (CollateClause *) n;
if (*collClause)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple COLLATE clauses not allowed"),
parser_errposition(c->location)));
*collClause = c;
}
else
elog(ERROR, "unexpected node type %d", (int) n->type);
/* remove non-Constraint nodes from qualList */
qualList = list_delete_cell(qualList, cell, prev);
}
*constraintList = qualList;
}
/*
* Process result of ConstraintAttributeSpec, and set appropriate bool flags
* in the output command node. Pass NULL for any flags the particular
* command doesn't support.
*/
static void
processCASbits(int cas_bits, int location, const char *constrType,
bool *deferrable, bool *initdeferred, bool *not_valid,
bool *no_inherit, core_yyscan_t yyscanner)
{
/* defaults */
if (deferrable)
*deferrable = false;
if (initdeferred)
*initdeferred = false;
if (not_valid)
*not_valid = false;
if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
{
if (deferrable)
*deferrable = true;
else
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s is CHECK, UNIQUE, or similar */
errmsg("%s constraints cannot be marked DEFERRABLE",
constrType),
parser_errposition(location)));
}
if (cas_bits & CAS_INITIALLY_DEFERRED)
{
if (initdeferred)
*initdeferred = true;
else
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s is CHECK, UNIQUE, or similar */
errmsg("%s constraints cannot be marked DEFERRABLE",
constrType),
parser_errposition(location)));
}
if (cas_bits & CAS_NOT_VALID)
{
if (not_valid)
*not_valid = true;
else
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s is CHECK, UNIQUE, or similar */
errmsg("%s constraints cannot be marked NOT VALID",
constrType),
parser_errposition(location)));
}
if (cas_bits & CAS_NO_INHERIT)
{
if (no_inherit)
*no_inherit = true;
else
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/* translator: %s is CHECK, UNIQUE, or similar */
errmsg("%s constraints cannot be marked NO INHERIT",
constrType),
parser_errposition(location)));
}
}
/*----------
* Recursive view transformation
*
* Convert
*
* CREATE RECURSIVE VIEW relname (aliases) AS query
*
* to
*
* CREATE VIEW relname (aliases) AS
* WITH RECURSIVE relname (aliases) AS (query)
* SELECT aliases FROM relname
*
* Actually, just the WITH ... part, which is then inserted into the original
* view definition as the query.
* ----------
*/
static Node *
makeRecursiveViewSelect(char *relname, List *aliases, Node *query)
{
SelectStmt *s = makeNode(SelectStmt);
WithClause *w = makeNode(WithClause);
CommonTableExpr *cte = makeNode(CommonTableExpr);
List *tl = NIL;
ListCell *lc;
/* create common table expression */
cte->ctename = relname;
cte->aliascolnames = aliases;
cte->ctequery = query;
cte->location = -1;
/* create WITH clause and attach CTE */
w->recursive = true;
w->ctes = list_make1(cte);
w->location = -1;
/* create target list for the new SELECT from the alias list of the
* recursive view specification */
foreach (lc, aliases)
{
ResTarget *rt = makeNode(ResTarget);
rt->name = NULL;
rt->indirection = NIL;
rt->val = makeColumnRef(strVal(lfirst(lc)), NIL, -1, 0);
rt->location = -1;
tl = lappend(tl, rt);
}
/* create new SELECT combining WITH clause, target list, and fake FROM
* clause */
s->withClause = w;
s->targetList = tl;
s->fromClause = list_make1(makeRangeVar(NULL, relname, -1));
return (Node *) s;
}
/* parser_init()
* Initialize to parse one query string
*/
void
parser_init(base_yy_extra_type *yyext)
{
yyext->parsetree = NIL; /* in case grammar forgets to set it */
}“PostgreSQL怎么實現用戶自定義”的內容就介紹到這里了，感謝大家的閱讀。如果想了解更多行業相關的知識可以關注億速云網站，小編將為大家輸出更多高質量的實用文章！
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