diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index f66e1449d8..f2ac4e51f1 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -158,6 +158,10 @@ typedef struct Expr * than a heap column. (In ForeignScan and CustomScan plan nodes, INDEX_VAR * is abused to signify references to columns of a custom scan tuple type.) * + * ROWID_VAR is used in the planner to identify nonce variables that carry + * row identity information during UPDATE/DELETE. This value should never + * be seen outside the planner. + * * In the parser, varnosyn and varattnosyn are either identical to * varno/varattno, or they specify the column's position in an aliased JOIN * RTE that hides the semantic referent RTE's refname. This is a syntactic @@ -171,6 +175,7 @@ typedef struct Expr #define INNER_VAR 65000 /* reference to inner subplan */ #define OUTER_VAR 65001 /* reference to outer subplan */ #define INDEX_VAR 65002 /* reference to index column */ +#define ROWID_VAR 65003 /* row identity column during planning */ #define IS_SPECIAL_VARNO(varno) ((varno) >= INNER_VAR) @@ -1386,13 +1391,14 @@ typedef struct InferenceElem * column for the item; so there may be missing or out-of-order resnos. * It is even legal to have duplicated resnos; consider * UPDATE table SET arraycol[1] = ..., arraycol[2] = ..., ... - * The two meanings come together in the executor, because the planner - * transforms INSERT/UPDATE tlists into a normalized form with exactly - * one entry for each column of the destination table. Before that's - * happened, however, it is risky to assume that resno == position. - * Generally get_tle_by_resno() should be used rather than list_nth() - * to fetch tlist entries by resno, and only in SELECT should you assume - * that resno is a unique identifier. + * In an INSERT, the rewriter and planner will normalize the tlist by + * reordering it into physical column order and filling in default values + * for any columns not assigned values by the original query. In an UPDATE, + * after the rewriter merges multiple assignments for the same column, the + * planner extracts the target-column numbers into a separate "update_colnos" + * list, and then renumbers the tlist elements serially. Thus, tlist resnos + * match ordinal position in all tlists seen by the executor; but it is wrong + * to assume that before planning has happened. * * resname is required to represent the correct column name in non-resjunk * entries of top-level SELECT targetlists, since it will be used as the |