src/backend/commands/conversioncmds.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * conversioncmds.c
   4  *        conversion creation command support code
   5  *
   6  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/commands/conversioncmds.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #include "postgres.h"
  16
  17 #include "catalog/pg_conversion.h"
  18 #include "catalog/pg_namespace.h"
  19 #include "catalog/pg_proc.h"
  20 #include "catalog/pg_type.h"
  21 #include "commands/conversioncmds.h"
  22 #include "mb/pg_wchar.h"
  23 #include "miscadmin.h"
  24 #include "parser/parse_func.h"
  25 #include "utils/acl.h"
  26 #include "utils/lsyscache.h"
  27
  28 /*
  29  * CREATE CONVERSION
  30  */
  31 ObjectAddress
  32 CreateConversionCommand(CreateConversionStmt *stmt)
  33 {
  34         Oid                     namespaceId;
  35         char       *conversion_name;
  36         AclResult       aclresult;
  37         int                     from_encoding;
  38         int                     to_encoding;
  39         Oid                     funcoid;
  40         const char *from_encoding_name = stmt->for_encoding_name;
  41         const char *to_encoding_name = stmt->to_encoding_name;
  42         List       *func_name = stmt->func_name;
  43         static const Oid funcargs[] = {INT4OID, INT4OID, CSTRINGOID, INTERNALOID, INT4OID, BOOLOID};
  44         char            result[1];
  45         Datum           funcresult;
  46
  47         /* Convert list of names to a name and namespace */
  48         namespaceId = QualifiedNameGetCreationNamespace(stmt->conversion_name,
  49                                                                                                         &conversion_name);
  50
  51         /* Check we have creation rights in target namespace */
  52         aclresult = object_aclcheck(NamespaceRelationId, namespaceId, GetUserId(), ACL_CREATE);
  53         if (aclresult != ACLCHECK_OK)
  54                 aclcheck_error(aclresult, OBJECT_SCHEMA,
  55                                            get_namespace_name(namespaceId));
  56
  57         /* Check the encoding names */
  58         from_encoding = pg_char_to_encoding(from_encoding_name);
  59         if (from_encoding < 0)
  60                 ereport(ERROR,
  61                                 (errcode(ERRCODE_UNDEFINED_OBJECT),
  62                                  errmsg("source encoding \"%s\" does not exist",
  63                                                 from_encoding_name)));
  64
  65         to_encoding = pg_char_to_encoding(to_encoding_name);
  66         if (to_encoding < 0)
  67                 ereport(ERROR,
  68                                 (errcode(ERRCODE_UNDEFINED_OBJECT),
  69                                  errmsg("destination encoding \"%s\" does not exist",
  70                                                 to_encoding_name)));
  71
  72         /*
  73          * We consider conversions to or from SQL_ASCII to be meaningless.  (If
  74          * you wish to change this, note that pg_do_encoding_conversion() and its
  75          * sister functions have hard-wired fast paths for any conversion in which
  76          * the source or target encoding is SQL_ASCII, so that an encoding
  77          * conversion function declared for such a case will never be used.)
  78          */
  79         if (from_encoding == PG_SQL_ASCII || to_encoding == PG_SQL_ASCII)
  80                 ereport(ERROR,
  81                                 (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  82                                  errmsg("encoding conversion to or from \"SQL_ASCII\" is not supported")));
  83
  84         /*
  85          * Check the existence of the conversion function. Function name could be
  86          * a qualified name.
  87          */
  88         funcoid = LookupFuncName(func_name, sizeof(funcargs) / sizeof(Oid),
  89                                                          funcargs, false);
  90
  91         /* Check it returns int4, else it's probably the wrong function */
  92         if (get_func_rettype(funcoid) != INT4OID)
  93                 ereport(ERROR,
  94                                 (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  95                                  errmsg("encoding conversion function %s must return type %s",
  96                                                 NameListToString(func_name), "integer")));
  97
  98         /* Check we have EXECUTE rights for the function */
  99         aclresult = object_aclcheck(ProcedureRelationId, funcoid, GetUserId(), ACL_EXECUTE);
 100         if (aclresult != ACLCHECK_OK)
 101                 aclcheck_error(aclresult, OBJECT_FUNCTION,
 102                                            NameListToString(func_name));
 103
 104         /*
 105          * Check that the conversion function is suitable for the requested source
 106          * and target encodings. We do that by calling the function with an empty
 107          * string; the conversion function should throw an error if it can't
 108          * perform the requested conversion.
 109          */
 110         funcresult = OidFunctionCall6(funcoid,
 111                                                                   Int32GetDatum(from_encoding),
 112                                                                   Int32GetDatum(to_encoding),
 113                                                                   CStringGetDatum(""),
 114                                                                   CStringGetDatum(result),
 115                                                                   Int32GetDatum(0),
 116                                                                   BoolGetDatum(false));
 117
 118         /*
 119          * The function should return 0 for empty input. Might as well check that,
 120          * too.
 121          */
 122         if (DatumGetInt32(funcresult) != 0)
 123                 ereport(ERROR,
 124                                 (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
 125                                  errmsg("encoding conversion function %s returned incorrect result for empty input",
 126                                                 NameListToString(func_name))));
 127
 128         /*
 129          * All seem ok, go ahead (possible failure would be a duplicate conversion
 130          * name)
 131          */
 132         return ConversionCreate(conversion_name, namespaceId, GetUserId(),
 133                                                         from_encoding, to_encoding, funcoid, stmt->def);
 134 }