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e812458b27
* Buffer refcount cleanup (per my "progress report" to pghackers, 9/22). * Add links to backend PROC structs to sinval's array of per-backend info, and use these links for routines that need to check the state of all backends (rather than the slow, complicated search of the ShmemIndex hashtable that was used before). Add databaseOID to PROC structs. * Use this to implement an interlock that prevents DESTROY DATABASE of a database containing running backends. (It's a little tricky to prevent a concurrently-starting backend from getting in there, since the new backend is not able to lock anything at the time it tries to look up its database in pg_database. My solution is to recheck that the DB is OK at the end of InitPostgres. It may not be a 100% solution, but it's a lot better than no interlock at all...) * In ALTER TABLE RENAME, flush buffers for the relation before doing the rename of the physical files, to ensure we don't get failures later from mdblindwrt(). * Update TRUNCATE patch so that it actually compiles against current sources :-(. You should do "make clean all" after pulling these changes. |
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| .. | ||
| aclchk.c | ||
| catalog.c | ||
| genbki.sh.in | ||
| heap.c | ||
| index.c | ||
| indexing.c | ||
| Makefile | ||
| pg_aggregate.c | ||
| pg_operator.c | ||
| pg_proc.c | ||
| pg_type.c | ||
| README | ||
$Header: /cvsroot/pgsql/src/backend/catalog/README,v 1.1.1.1 1996/07/09 06:21:15 scrappy Exp $ This directory contains .c files that manipulate the system catalogs as well as .h files that define the structure of the system catalogs. When the compile-time scripts (such as Gen_fmgrtab.sh and genbki.sh) execute, they grep the DATA statements out of the .h files and munge these in order to generate the .bki files. The .bki files are then used as input to initdb (which is just a wrapper around postgres running single-user in bootstrapping mode) in order to generate the initial (template) system catalog relation files. ----------------------------------------------------------------- People who are going to hose around with the .h files should be aware of the following facts: - It is very important that the DATA statements be properly formatted (e.g., no broken lines, proper use of white-space and _null_). The scripts are line-oriented and break easily. In addition, the only documentation on the proper format for them is the code in the bootstrap/ directory. Just be careful when adding new DATA statements. - Some catalogs require that OIDs be preallocated to tuples because certain catalogs contain circular references. For example, pg_type contains pointers into pg_proc (pg_type.typinput), and pg_proc contains back-pointers into pg_type (pg_proc.proargtypes). In these cases, the references may be explicitly set by use of the "OID =" clause of the .bki insert statement. If no such pointers are required to a given tuple, then the OID may be set to the wildcard value 0 (i.e., the system generates a random OID in the usual way). If you need to find a valid OID for a set of tuples that refer to each other, use the unused_oids script. It generates inclusive ranges of *unused* OIDs (i.e., the line "45-900" means OIDs 45 through 900 have not been allocated yet). However, you should not rely 100% on this script, since it only looks at the .h files in the catalog/ directory. Do a pg_grepsrc (recursive grep) of the source tree to insure that there aren't any hidden crocks (i.e., explicit use of a numeric OID) anywhere in the code. ----------------------------------------------------------------- When munging the .c files, you should be aware of certain conventions: - The system catalog cache code (and most catalog-munging code in general) assumes that the fixed-length portion of all system catalog tuples are in fact present. That is, only the variable-length portions of a catalog tuple are assumed to be permitted to be non-NULL. For example, if you set pg_type.typdelim to be NULL, a piece of code will likely perform "typetup->typdelim" (or, worse, "typetyp->typelem", which follows typdelim). This will result in random errors or even segmentation violations. Hence, do NOT insert catalog tuples that contain NULL attributes except in their variable-length portions! - Modification of the catalogs must be performed with the proper updating of catalog indexes! That is, several catalogs have indexes on them; when you munge them using the executor, the executor will take care of doing the index updates, but if you make direct access method calls to insert new or modified tuples into a heap, you must also make the calls to insert the tuple into ALL of its indexes! If not, the new tuple will generally be "invisible" to the system because most of the accesses to the catalogs in question will be through the associated indexes.