Hi, While digging through the archives, I found a thread from a couple years back about syscache performance. There was an idea [1] to generate the cache control data at compile time. That would to remove the need to perform database access to complete cache initialization, as well as the need to check in various places whether initialization has happened.
If this were done, catcache.c:InitCatCachePhase2() and catcache.c:CatalogCacheInitializeCache() would disappear, and syscache.c:InitCatalogCachePhase2() could be replaced by code that simply opens the relations when writing new init files. Another possibility this opens up is making the SysCacheRelationOid and SysCacheSupportingRelOid arrays constant data as well. Here's a basic design sketch: 1. Generate the current syscache cacheinfo[] array and cacheid enum by adding a couple arguments to the declarations for system indexes, as in: #define DECLARE_UNIQUE_INDEX(name,oid,oid_macro,cacheid,num_buckets,decl) extern int no_such_variable DECLARE_UNIQUE_INDEX(pg_amop_opr_fam_index, 2654, AccessMethodOperatorIndexId, AMOPOPID, 64, on pg_amop using btree(amopopr oid_ops, amoppurpose char_ops, amopfamily oid_ops)); DECLARE_UNIQUE_INDEX(pg_amop_oid_index, 2756, AccessMethodOperatorOidIndexId, -, 0, on pg_amop using btree(oid oid_ops)); ...and add in data we already know how to parse from the catalog headers. Note that the last example has '-' and '0' to mean "no cache". (The index oid macro is superfluous there, but kept for consistency.) 2. Expand the cacheinfo[] element structs with the rest of the constant data: Relname, and relisshared are straightforward. For eq/hash functions, we could add metadata attributes to pg_type.dat for the relevant types. Tuple descriptors would get their attrs from schemapg.h. 3. Simplify cat/syscache.c Is this something worth doing? [1] https://www.postgresql.org/message-id/1295.1507918074%40sss.pgh.pa.us -- John Naylor https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
