Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * tupconvert.c
       4             :  *    Tuple conversion support.
       5             :  *
       6             :  * These functions provide conversion between rowtypes that are logically
       7             :  * equivalent but might have columns in a different order or different sets of
       8             :  * dropped columns.
       9             :  *
      10             :  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
      11             :  * Portions Copyright (c) 1994, Regents of the University of California
      12             :  *
      13             :  *
      14             :  * IDENTIFICATION
      15             :  *    src/backend/access/common/tupconvert.c
      16             :  *
      17             :  *-------------------------------------------------------------------------
      18             :  */
      19             : #include "postgres.h"
      20             : 
      21             : #include "access/tupconvert.h"
      22             : #include "executor/tuptable.h"
      23             : 
      24             : 
      25             : /*
      26             :  * The conversion setup routines have the following common API:
      27             :  *
      28             :  * The setup routine checks using attmap.c whether the given source and
      29             :  * destination tuple descriptors are logically compatible.  If not, it throws
      30             :  * an error.  If so, it returns NULL if they are physically compatible (ie, no
      31             :  * conversion is needed), else a TupleConversionMap that can be used by
      32             :  * execute_attr_map_tuple or execute_attr_map_slot to perform the conversion.
      33             :  *
      34             :  * The TupleConversionMap, if needed, is palloc'd in the caller's memory
      35             :  * context.  Also, the given tuple descriptors are referenced by the map,
      36             :  * so they must survive as long as the map is needed.
      37             :  *
      38             :  * The caller must supply a suitable primary error message to be used if
      39             :  * a compatibility error is thrown.  Recommended coding practice is to use
      40             :  * gettext_noop() on this string, so that it is translatable but won't
      41             :  * actually be translated unless the error gets thrown.
      42             :  *
      43             :  *
      44             :  * Implementation notes:
      45             :  *
      46             :  * The key component of a TupleConversionMap is an attrMap[] array with
      47             :  * one entry per output column.  This entry contains the 1-based index of
      48             :  * the corresponding input column, or zero to force a NULL value (for
      49             :  * a dropped output column).  The TupleConversionMap also contains workspace
      50             :  * arrays.
      51             :  */
      52             : 
      53             : 
      54             : /*
      55             :  * Set up for tuple conversion, matching input and output columns by
      56             :  * position.  (Dropped columns are ignored in both input and output.)
      57             :  */
      58             : TupleConversionMap *
      59        9500 : convert_tuples_by_position(TupleDesc indesc,
      60             :                            TupleDesc outdesc,
      61             :                            const char *msg)
      62             : {
      63             :     TupleConversionMap *map;
      64             :     int         n;
      65             :     AttrMap    *attrMap;
      66             : 
      67             :     /* Verify compatibility and prepare attribute-number map */
      68        9500 :     attrMap = build_attrmap_by_position(indesc, outdesc, msg);
      69             : 
      70        9468 :     if (attrMap == NULL)
      71             :     {
      72             :         /* runtime conversion is not needed */
      73        9374 :         return NULL;
      74             :     }
      75             : 
      76             :     /* Prepare the map structure */
      77          94 :     map = (TupleConversionMap *) palloc(sizeof(TupleConversionMap));
      78          94 :     map->indesc = indesc;
      79          94 :     map->outdesc = outdesc;
      80          94 :     map->attrMap = attrMap;
      81             :     /* preallocate workspace for Datum arrays */
      82          94 :     n = outdesc->natts + 1;      /* +1 for NULL */
      83          94 :     map->outvalues = (Datum *) palloc(n * sizeof(Datum));
      84          94 :     map->outisnull = (bool *) palloc(n * sizeof(bool));
      85          94 :     n = indesc->natts + 1;       /* +1 for NULL */
      86          94 :     map->invalues = (Datum *) palloc(n * sizeof(Datum));
      87          94 :     map->inisnull = (bool *) palloc(n * sizeof(bool));
      88          94 :     map->invalues[0] = (Datum) 0;    /* set up the NULL entry */
      89          94 :     map->inisnull[0] = true;
      90             : 
      91          94 :     return map;
      92             : }
      93             : 
      94             : /*
      95             :  * Set up for tuple conversion, matching input and output columns by name.
      96             :  * (Dropped columns are ignored in both input and output.)  This is intended
      97             :  * for use when the rowtypes are related by inheritance, so we expect an exact
      98             :  * match of both type and typmod.  The error messages will be a bit unhelpful
      99             :  * unless both rowtypes are named composite types.
     100             :  */
     101             : TupleConversionMap *
     102        3194 : convert_tuples_by_name(TupleDesc indesc,
     103             :                        TupleDesc outdesc)
     104             : {
     105             :     AttrMap    *attrMap;
     106             : 
     107             :     /* Verify compatibility and prepare attribute-number map */
     108        3194 :     attrMap = build_attrmap_by_name_if_req(indesc, outdesc, false);
     109             : 
     110        3194 :     if (attrMap == NULL)
     111             :     {
     112             :         /* runtime conversion is not needed */
     113        2434 :         return NULL;
     114             :     }
     115             : 
     116         760 :     return convert_tuples_by_name_attrmap(indesc, outdesc, attrMap);
     117             : }
     118             : 
     119             : /*
     120             :  * Set up tuple conversion for input and output TupleDescs using the given
     121             :  * AttrMap.
     122             :  */
     123             : TupleConversionMap *
     124        2138 : convert_tuples_by_name_attrmap(TupleDesc indesc,
     125             :                                TupleDesc outdesc,
     126             :                                AttrMap *attrMap)
     127             : {
     128        2138 :     int         n = outdesc->natts;
     129             :     TupleConversionMap *map;
     130             : 
     131             :     Assert(attrMap != NULL);
     132             : 
     133             :     /* Prepare the map structure */
     134        2138 :     map = (TupleConversionMap *) palloc(sizeof(TupleConversionMap));
     135        2138 :     map->indesc = indesc;
     136        2138 :     map->outdesc = outdesc;
     137        2138 :     map->attrMap = attrMap;
     138             :     /* preallocate workspace for Datum arrays */
     139        2138 :     map->outvalues = (Datum *) palloc(n * sizeof(Datum));
     140        2138 :     map->outisnull = (bool *) palloc(n * sizeof(bool));
     141        2138 :     n = indesc->natts + 1;       /* +1 for NULL */
     142        2138 :     map->invalues = (Datum *) palloc(n * sizeof(Datum));
     143        2138 :     map->inisnull = (bool *) palloc(n * sizeof(bool));
     144        2138 :     map->invalues[0] = (Datum) 0;    /* set up the NULL entry */
     145        2138 :     map->inisnull[0] = true;
     146             : 
     147        2138 :     return map;
     148             : }
     149             : 
     150             : /*
     151             :  * Perform conversion of a tuple according to the map.
     152             :  */
     153             : HeapTuple
     154      106734 : execute_attr_map_tuple(HeapTuple tuple, TupleConversionMap *map)
     155             : {
     156      106734 :     AttrMap    *attrMap = map->attrMap;
     157      106734 :     Datum      *invalues = map->invalues;
     158      106734 :     bool       *inisnull = map->inisnull;
     159      106734 :     Datum      *outvalues = map->outvalues;
     160      106734 :     bool       *outisnull = map->outisnull;
     161             :     int         i;
     162             : 
     163             :     /*
     164             :      * Extract all the values of the old tuple, offsetting the arrays so that
     165             :      * invalues[0] is left NULL and invalues[1] is the first source attribute;
     166             :      * this exactly matches the numbering convention in attrMap.
     167             :      */
     168      106734 :     heap_deform_tuple(tuple, map->indesc, invalues + 1, inisnull + 1);
     169             : 
     170             :     /*
     171             :      * Transpose into proper fields of the new tuple.
     172             :      */
     173             :     Assert(attrMap->maplen == map->outdesc->natts);
     174      424652 :     for (i = 0; i < attrMap->maplen; i++)
     175             :     {
     176      317918 :         int         j = attrMap->attnums[i];
     177             : 
     178      317918 :         outvalues[i] = invalues[j];
     179      317918 :         outisnull[i] = inisnull[j];
     180             :     }
     181             : 
     182             :     /*
     183             :      * Now form the new tuple.
     184             :      */
     185      106734 :     return heap_form_tuple(map->outdesc, outvalues, outisnull);
     186             : }
     187             : 
     188             : /*
     189             :  * Perform conversion of a tuple slot according to the map.
     190             :  */
     191             : TupleTableSlot *
     192      143418 : execute_attr_map_slot(AttrMap *attrMap,
     193             :                       TupleTableSlot *in_slot,
     194             :                       TupleTableSlot *out_slot)
     195             : {
     196             :     Datum      *invalues;
     197             :     bool       *inisnull;
     198             :     Datum      *outvalues;
     199             :     bool       *outisnull;
     200             :     int         outnatts;
     201             :     int         i;
     202             : 
     203             :     /* Sanity checks */
     204             :     Assert(in_slot->tts_tupleDescriptor != NULL &&
     205             :            out_slot->tts_tupleDescriptor != NULL);
     206             :     Assert(in_slot->tts_values != NULL && out_slot->tts_values != NULL);
     207             : 
     208      143418 :     outnatts = out_slot->tts_tupleDescriptor->natts;
     209             : 
     210             :     /* Extract all the values of the in slot. */
     211      143418 :     slot_getallattrs(in_slot);
     212             : 
     213             :     /* Before doing the mapping, clear any old contents from the out slot */
     214      143418 :     ExecClearTuple(out_slot);
     215             : 
     216      143418 :     invalues = in_slot->tts_values;
     217      143418 :     inisnull = in_slot->tts_isnull;
     218      143418 :     outvalues = out_slot->tts_values;
     219      143418 :     outisnull = out_slot->tts_isnull;
     220             : 
     221             :     /* Transpose into proper fields of the out slot. */
     222      578290 :     for (i = 0; i < outnatts; i++)
     223             :     {
     224      434872 :         int         j = attrMap->attnums[i] - 1;
     225             : 
     226             :         /* attrMap->attnums[i] == 0 means it's a NULL datum. */
     227      434872 :         if (j == -1)
     228             :         {
     229        2472 :             outvalues[i] = (Datum) 0;
     230        2472 :             outisnull[i] = true;
     231             :         }
     232             :         else
     233             :         {
     234      432400 :             outvalues[i] = invalues[j];
     235      432400 :             outisnull[i] = inisnull[j];
     236             :         }
     237             :     }
     238             : 
     239      143418 :     ExecStoreVirtualTuple(out_slot);
     240             : 
     241      143418 :     return out_slot;
     242             : }
     243             : 
     244             : /*
     245             :  * Perform conversion of bitmap of columns according to the map.
     246             :  *
     247             :  * The input and output bitmaps are offset by
     248             :  * FirstLowInvalidHeapAttributeNumber to accommodate system cols, like the
     249             :  * column-bitmaps in RangeTblEntry.
     250             :  */
     251             : Bitmapset *
     252         486 : execute_attr_map_cols(AttrMap *attrMap, Bitmapset *in_cols)
     253             : {
     254             :     Bitmapset  *out_cols;
     255             :     int         out_attnum;
     256             : 
     257             :     /* fast path for the common trivial case */
     258         486 :     if (in_cols == NULL)
     259           0 :         return NULL;
     260             : 
     261             :     /*
     262             :      * For each output column, check which input column it corresponds to.
     263             :      */
     264         486 :     out_cols = NULL;
     265             : 
     266         486 :     for (out_attnum = FirstLowInvalidHeapAttributeNumber;
     267        6200 :          out_attnum <= attrMap->maplen;
     268        5714 :          out_attnum++)
     269             :     {
     270             :         int         in_attnum;
     271             : 
     272        5714 :         if (out_attnum < 0)
     273             :         {
     274             :             /* System column. No mapping. */
     275        3402 :             in_attnum = out_attnum;
     276             :         }
     277        2312 :         else if (out_attnum == 0)
     278         486 :             continue;
     279             :         else
     280             :         {
     281             :             /* normal user column */
     282        1826 :             in_attnum = attrMap->attnums[out_attnum - 1];
     283             : 
     284        1826 :             if (in_attnum == 0)
     285         142 :                 continue;
     286             :         }
     287             : 
     288        5086 :         if (bms_is_member(in_attnum - FirstLowInvalidHeapAttributeNumber, in_cols))
     289         520 :             out_cols = bms_add_member(out_cols, out_attnum - FirstLowInvalidHeapAttributeNumber);
     290             :     }
     291             : 
     292         486 :     return out_cols;
     293             : }
     294             : 
     295             : /*
     296             :  * Free a TupleConversionMap structure.
     297             :  */
     298             : void
     299         134 : free_conversion_map(TupleConversionMap *map)
     300             : {
     301             :     /* indesc and outdesc are not ours to free */
     302         134 :     free_attrmap(map->attrMap);
     303         134 :     pfree(map->invalues);
     304         134 :     pfree(map->inisnull);
     305         134 :     pfree(map->outvalues);
     306         134 :     pfree(map->outisnull);
     307         134 :     pfree(map);
     308         134 : }