diff options
| -rw-r--r-- | src/backend/catalog/pg_attribute.h | 24 | ||||
| -rw-r--r-- | src/backend/catalog/pg_type.h | 47 |
2 files changed, 63 insertions, 8 deletions
diff --git a/src/backend/catalog/pg_attribute.h b/src/backend/catalog/pg_attribute.h index 4de58840052..16294621991 100644 --- a/src/backend/catalog/pg_attribute.h +++ b/src/backend/catalog/pg_attribute.h @@ -7,7 +7,7 @@ * * Copyright (c) 1994, Regents of the University of California * - * $Id: pg_attribute.h,v 1.2 1996/08/21 04:25:47 scrappy Exp $ + * $Id: pg_attribute.h,v 1.3 1996/08/24 20:56:13 scrappy Exp $ * * NOTES * the genbki.sh script reads this file and generates .bki @@ -44,13 +44,19 @@ CATALOG(pg_attribute) BOOTSTRAP { Oid attrelid; NameData attname; Oid atttypid; + /* atttypid is the OID of the instance in Catalog Class pg_type that + defines the data type of this attribute (e.g. int4). Information in + that instance is redundant with the attlen, attbyval, and attalign + attributes of this instance, so they had better match or Postgres + will fail. + */ Oid attdefrel; int4 attnvals; Oid atttyparg; /* type arg for arrays/spquel/procs */ int2 attlen; - /* attlen is the number of bytes we use to represent the value - of this attribute, e.g. 4 for an int4. But for a variable length - attribute, attlen is -1. + /* attlen is a copy of the typlen field from pg_type for this + attribute. See atttypid above. See struct TypeTupleFormData for + definition. */ int2 attnum; /* attnum is the "attribute number" for the attribute: A @@ -68,6 +74,10 @@ CATALOG(pg_attribute) BOOTSTRAP { */ int2 attbound; bool attbyval; + /* attbyval is a copy of the typbyval field from pg_type for this + attribute. See atttypid above. See struct TypeTupleFormData for + definition. + */ bool attcanindex; Oid attproc; /* spquel? */ int4 attnelems; @@ -80,7 +90,11 @@ CATALOG(pg_attribute) BOOTSTRAP { walking process. */ bool attisset; - char attalign; /* alignment (c=char, s=short, i=int, d=double) */ + char attalign; + /* attalign is a copy of the typalign field from pg_type for this + attribute. See atttypid above. See struct TypeTupleFormData for + definition. + */ } FormData_pg_attribute; /* diff --git a/src/backend/catalog/pg_type.h b/src/backend/catalog/pg_type.h index 029c25a781f..39ebdb6bdaf 100644 --- a/src/backend/catalog/pg_type.h +++ b/src/backend/catalog/pg_type.h @@ -7,7 +7,7 @@ * * Copyright (c) 1994, Regents of the University of California * - * $Id: pg_type.h,v 1.3 1996/07/19 05:21:28 scrappy Exp $ + * $Id: pg_type.h,v 1.4 1996/08/24 20:56:16 scrappy Exp $ * * NOTES * the genbki.sh script reads this file and generates .bki @@ -30,14 +30,34 @@ /* ---------------- * pg_type definition. cpp turns this into * typedef struct FormData_pg_type + * + * Some of the values in a pg_type instance are copied into + * pg_attribute intances. Some parts of Postgres use the pg_type copy, + * while others use the pg_attribute copy, so they must match. + * See struct FormData_pg_attribute for details. * ---------------- */ CATALOG(pg_type) BOOTSTRAP { NameData typname; Oid typowner; int2 typlen; + /* typlen is the number of bytes we use to represent a value of + this type, e.g. 4 for an int4. But for a variable length + attribute, typlen is -1. + */ int2 typprtlen; bool typbyval; + /* typbyval determines whether internal Postgres routines pass a value + of this type by value or by reference. Postgres uses a 4 byte + area for passing class data, so if the value is not 1, 2, + or 4 bytes long, Postgres does not have the option of passing by + value and ignores typbyval. + + (I don't understand why this attribute exists. The above description + may be an oversimplification. Also, there appear to be bugs in which + Postgres doesn't ignore typbyval when it should, but I'm + afraid to change them until I see proof of damage. -BRYANH 96.08). + */ char typtype; bool typisdefined; char typdelim; @@ -47,7 +67,23 @@ CATALOG(pg_type) BOOTSTRAP { regproc typoutput; regproc typreceive; regproc typsend; - char typalign; /* alignment (c=char, s=short, i=int, d=double) */ + char typalign; + /* typalign is the alignment required when storing a value of this + type. It applies to storage on disk as well as most representations + of the value inside Postgres. When multiple values are stored + consecutively, such as in the representation of a complete tuple + on disk, padding is inserted before a datum of this type so that it + begins on the specified boundary. The alignment reference is the + beginning of the first datum in the sequence. + + 'c' = 1 byte alignment. + 's' = 2 byte alignment. + 'i' = 4 byte alignment. + 'd' = 8 byte alignment. + + (This might actually be flexible depending on machine architecture, + but I doubt it - BRYANH 96.08). + */ text typdefault; /* VARIABLE LENGTH FIELD */ } TypeTupleFormData; @@ -87,6 +123,11 @@ typedef TypeTupleFormData *TypeTupleForm; /* keep the following ordered by OID so that later changes can be made easier*/ +/* Make sure the typlen, typbyval, and typalign values here match the initial + values for attlen, attbyval, and attalign in both places in pg_attribute.h + for every instance. +*/ + /* OIDS 1 - 99 */ DATA(insert OID = 16 ( bool PGUID 1 1 t b t \054 0 0 boolin boolout boolin boolout c _null_ )); @@ -95,7 +136,7 @@ DATA(insert OID = 16 ( bool PGUID 1 1 t b t \054 0 0 boolin boolout DATA(insert OID = 17 ( bytea PGUID -1 -1 f b t \054 0 18 byteain byteaout byteain byteaout i _null_ )); DATA(insert OID = 18 ( char PGUID 1 1 t b t \054 0 0 charin charout charin charout c _null_ )); -DATA(insert OID = 19 ( name PGUID NAMEDATALEN NAMEDATALEN f b t \054 0 18 namein nameout namein nameout d _null_ )); +DATA(insert OID = 19 ( name PGUID NAMEDATALEN NAMEDATALEN f b t \054 0 18 namein nameout namein nameout i _null_ )); DATA(insert OID = 20 ( char16 PGUID 16 16 f b t \054 0 18 char16in char16out char16in char16out i _null_ )); /*DATA(insert OID = 20 ( dt PGUID 4 10 t b t \054 0 0 dtin dtout dtin dtout i _null_ )); */ DATA(insert OID = 21 ( int2 PGUID 2 5 t b t \054 0 0 int2in int2out int2in int2out s _null_ )); |