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Diffstat (limited to 'doc/FAQ_DEV')
| -rw-r--r-- | doc/FAQ_DEV | 76 |
1 files changed, 63 insertions, 13 deletions
diff --git a/doc/FAQ_DEV b/doc/FAQ_DEV index 8190358b8e4..c1f7dcda1ea 100644 --- a/doc/FAQ_DEV +++ b/doc/FAQ_DEV @@ -1,7 +1,7 @@ Developer's Frequently Asked Questions (FAQ) for PostgreSQL - Last updated: Fri Oct 2 15:21:32 EDT 1998 + Last updated: Mon Feb 22 17:15:06 EST 1999 Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us) @@ -67,7 +67,7 @@ s Third, you need to get mkid from ftp.postgresql.org. By running tools/make_mkid, an archive of source symbols can be created that can - be rapidly queried like grep or edited. + be rapidly queried like grep or edited. Others prefer glimpse. make_diff has tools to create patch diff files that can be applied to the distribution. @@ -105,22 +105,72 @@ s We do this because this allows a consistent way to pass data inside the backend in a flexible way. Every node has a NodeTag which - specifies what type of data is inside the Node. Lists are lists of - Nodes. lfirst(), lnext(), and foreach() are used to get, skip, and - traverse through Lists. + specifies what type of data is inside the Node. Lists are groups of + Nodes chained together as a forward-linked list. + Here are some of the List manipulation commands: + + lfirst(i) + return the data at list element i. + + lnext(i) + return the next list element after i. + + foreach(i, list) + loop through list, assigning each list element to i. It is + important to note that i is a List *, not the data in the List + element. You need to use lfirst(i) to get at the data. Here is + a typical code snipped that loops through a List containing Var + *'s and processes each one: + + + List *i, *list; + + foreach(i, list) + { + Var *var = lfirst(i); + + /* process var here */ + } + + lcons(node, list) + add node to the front of list, or create a new list with node + if list is NIL. + + lappend(list, node) + add node to the end of list. This is more expensive that lcons. + + nconc(list1, list2) + Concat list2 on to the end of list1. + + length(list) + return the length of the list. + + nth(i, list) + return the i'th element in list. + + lconsi, ... + There are integer versions of these: lconsi, lappendi, nthi. + List's containing integers instead of Node pointers are used to + hold list of relation object id's and other integer quantities. + You can print nodes easily inside gdb. First, to disable output - truncation: + truncation when you use the gdb print command: (gdb) set print elements 0 - You may then use either of the next two commands to print out List, - Node, and structure contents. The first prints in a short format, and - the second in a long format: + Instead of printing values in gdb format, you can use the next two + commands to print out List, Node, and structure contents in a verbose + format that is easier to understand. List's are unrolled into nodes, + and nodes are printed in detail. The first prints in a short format, + and the second in a long format: (gdb) call print(any_pointer) (gdb) call pprint(any_pointer) + The output appears in the postmaster log file, or on your screen if + you are running a backend directly without a postmaster. + 5) How do I add a feature or fix a bug? The source code is over 250,000 lines. Many problems/features are @@ -197,7 +247,7 @@ s } NameData; typedef NameData *Name; - Table, column, type, function, and view names that come in to the + Table, column, type, function, and view names that come into the backend via user queries are stored as variable-length, null-terminated character strings. @@ -244,12 +294,12 @@ s While scans automatically lock/unlock rows from the buffer cache, with heap_fetch(), you must pass a Buffer pointer, and ReleaseBuffer() it when completed. Once you have the row, you can get data that is common - to all tuples, like t_ctid and t_oid, by mererly accessing the + to all tuples, like t_self and t_oid, by mererly accessing the HeapTuple structure entries. If you need a table-specific column, you should take the HeapTuple pointer, and use the GETSTRUCT() macro to access the table-specific start of the tuple. You then cast the pointer as a Form_pg_proc pointer if you are accessing the pg_proc - table, or TypeTupleForm if you are accessing pg_type. You can then + table, or Form_pg_type if you are accessing pg_type. You can then access the columns by using a structure pointer: ((Form_pg_class) GETSTRUCT(tuple))->relnatts @@ -258,7 +308,7 @@ s is to use heap_tuplemodify() and pass it your palloc'ed tuple, and the values you want changed. It returns another palloc'ed tuple, which you pass to heap_replace(). You can delete tuples by passing the tuple's - t_ctid to heap_destroy(). Remember, tuples can be either system cache + t_self to heap_destroy(). Remember, tuples can be either system cache versions, which may go away soon after you get them, buffer cache version, which will go away when you heap_getnext(), heap_endscan, or ReleaseBuffer(), in the heap_fetch() case. Or it may be a palloc'ed |