diff options
Diffstat (limited to 'src/include/nodes/primnodes.h')
| -rw-r--r-- | src/include/nodes/primnodes.h | 42 |
1 files changed, 25 insertions, 17 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h index cdbe781c734..dd85908fe2f 100644 --- a/src/include/nodes/primnodes.h +++ b/src/include/nodes/primnodes.h @@ -390,14 +390,14 @@ typedef struct WindowFunc int location; /* token location, or -1 if unknown */ } WindowFunc; -/* ---------------- - * SubscriptingRef: describes a subscripting operation over a container - * (array, etc). +/* + * SubscriptingRef: describes a subscripting operation over a container + * (array, etc). * * A SubscriptingRef can describe fetching a single element from a container, - * fetching a part of container (e.g. array slice), storing a single element into - * a container, or storing a slice. The "store" cases work with an - * initial container value and a source value that is inserted into the + * fetching a part of a container (e.g. an array slice), storing a single + * element into a container, or storing a slice. The "store" cases work with + * an initial container value and a source value that is inserted into the * appropriate part of the container; the result of the operation is an * entire new modified container value. * @@ -410,23 +410,32 @@ typedef struct WindowFunc * * In the slice case, individual expressions in the subscript lists can be * NULL, meaning "substitute the array's current lower or upper bound". - * - * Note: the result datatype is the element type when fetching a single - * element; but it is the array type when doing subarray fetch or either - * type of store. + * (Non-array containers may or may not support this.) + * + * refcontainertype is the actual container type that determines the + * subscripting semantics. (This will generally be either the exposed type of + * refexpr, or the base type if that is a domain.) refelemtype is the type of + * the container's elements; this is saved for the use of the subscripting + * functions, but is not used by the core code. refrestype, reftypmod, and + * refcollid describe the type of the SubscriptingRef's result. In a store + * expression, refrestype will always match refcontainertype; in a fetch, + * it could be refelemtype for an element fetch, or refcontainertype for a + * slice fetch, or possibly something else as determined by type-specific + * subscripting logic. Likewise, reftypmod and refcollid will match the + * container's properties in a store, but could be different in a fetch. * * Note: for the cases where a container is returned, if refexpr yields a R/W - * expanded container, then the implementation is allowed to modify that object - * in-place and return the same object.) - * ---------------- + * expanded container, then the implementation is allowed to modify that + * object in-place and return the same object. */ typedef struct SubscriptingRef { Expr xpr; Oid refcontainertype; /* type of the container proper */ - Oid refelemtype; /* type of the container elements */ - int32 reftypmod; /* typmod of the container (and elements too) */ - Oid refcollid; /* OID of collation, or InvalidOid if none */ + Oid refelemtype; /* the container type's pg_type.typelem */ + Oid refrestype; /* type of the SubscriptingRef's result */ + int32 reftypmod; /* typmod of the result */ + Oid refcollid; /* collation of result, or InvalidOid if none */ List *refupperindexpr; /* expressions that evaluate to upper * container indexes */ List *reflowerindexpr; /* expressions that evaluate to lower @@ -434,7 +443,6 @@ typedef struct SubscriptingRef * container element */ Expr *refexpr; /* the expression that evaluates to a * container value */ - Expr *refassgnexpr; /* expression for the source value, or NULL if * fetch */ } SubscriptingRef; |