diff options
Diffstat (limited to 'src/include/nodes/parsenodes.h')
| -rw-r--r-- | src/include/nodes/parsenodes.h | 62 |
1 files changed, 36 insertions, 26 deletions
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h index 8f6cc25e0a..0da9b37907 100644 --- a/src/include/nodes/parsenodes.h +++ b/src/include/nodes/parsenodes.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.257 2004/06/02 21:01:09 momjian Exp $ + * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.258 2004/06/09 19:08:18 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -166,26 +166,26 @@ typedef struct TypeName * ColumnRef - specifies a reference to a column, or possibly a whole tuple * * The "fields" list must be nonempty; its last component may be "*" - * instead of a field name. Subscripts are optional. + * instead of a regular field name. + * + * Note: any array subscripting or selection of fields from composite columns + * is represented by an A_Indirection node above the ColumnRef. However, + * for simplicity in the normal case, initial field selection from a table + * name is represented within ColumnRef and not by adding A_Indirection. */ typedef struct ColumnRef { NodeTag type; List *fields; /* field names (list of Value strings) */ - List *indirection; /* subscripts (list of A_Indices) */ } ColumnRef; /* - * ParamRef - specifies a parameter reference - * - * The parameter could be qualified with field names and/or subscripts + * ParamRef - specifies a $n parameter reference */ typedef struct ParamRef { NodeTag type; int number; /* the number of the parameter */ - List *fields; /* field names (list of Value strings) */ - List *indirection; /* subscripts (list of A_Indices) */ } ParamRef; /* @@ -267,40 +267,50 @@ typedef struct A_Indices } A_Indices; /* - * ExprFieldSelect - select a field and/or array element from an expression + * A_Indirection - select a field and/or array element from an expression * - * This is used in the raw parsetree to represent selection from an - * arbitrary expression (not a column or param reference). Either - * fields or indirection may be NIL if not used. + * The indirection list can contain both A_Indices nodes (representing + * subscripting) and string Value nodes (representing field selection + * --- the string value is the name of the field to select). For example, + * a complex selection operation like + * (foo).field1[42][7].field2 + * would be represented with a single A_Indirection node having a 4-element + * indirection list. + * + * Note: as of Postgres 7.5, we don't support arrays of composite values, + * so cases in which a field select follows a subscript aren't actually + * semantically legal. However the parser is prepared to handle such. */ -typedef struct ExprFieldSelect +typedef struct A_Indirection { NodeTag type; Node *arg; /* the thing being selected from */ - List *fields; /* field names (list of Value strings) */ - List *indirection; /* subscripts (list of A_Indices) */ -} ExprFieldSelect; + List *indirection; /* subscripts and/or field names */ +} A_Indirection; /* * ResTarget - - * result target (used in target list of pre-transformed Parse trees) + * result target (used in target list of pre-transformed parse trees) * - * In a SELECT or INSERT target list, 'name' is either NULL or - * the column name assigned to the value. (If there is an 'AS ColumnLabel' - * clause, the grammar sets 'name' from it; otherwise 'name' is initially NULL - * and is filled in during the parse analysis phase.) - * The 'indirection' field is not used at all. + * In a SELECT or INSERT target list, 'name' is the column label from an + * 'AS ColumnLabel' clause, or NULL if there was none, and 'val' is the + * value expression itself. The 'indirection' field is not used. * - * In an UPDATE target list, 'name' is the name of the destination column, + * INSERT has a second ResTarget list which is the target-column-names list. + * Here, 'val' is not used, 'name' is the name of the destination column, * and 'indirection' stores any subscripts attached to the destination. - * That is, our representation is UPDATE table SET name [indirection] = val. + * + * In an UPDATE target list, 'name' is the name of the destination column, + * 'indirection' stores any subscripts attached to the destination, and + * 'val' is the expression to assign. + * + * See A_Indirection for more info about what can appear in 'indirection'. */ typedef struct ResTarget { NodeTag type; char *name; /* column name or NULL */ - List *indirection; /* subscripts for destination column, or - * NIL */ + List *indirection; /* subscripts and field names, or NIL */ Node *val; /* the value expression to compute or * assign */ } ResTarget; |