Cache Layer

Relation Cache and Attribute Cache have size 12 (MAX OPEN) in each which each entry in these arrays store the catalog entry for each.

===Can have upto 12 relations open at a time (MAX_OPEN)===

An entry of the relation cache stores the relation catalog entry, the rec-id (block & slot number) of the entry on the disk and some other runtime data. An entry of the attribute cache is a liked list where each node contains one of the attribute catalog entries for the relation, the corresponding rec-ids and some runtime metadata.

Relation Cache Table Structure

typedef struct RelCatEntry {
    unsigned char relName[ATTR_SIZE];
    int numAttrs;
    int numRecs;
    int firstBlk;
    int lastBlk;
    int numSlotsPerBlk;
} RelCatEntry;

typedef struct RelCacheEntry {
    RelCatEntry relCatEntry;
    bool dirty;
    RecId recId;
    RecId searchIndex;
} RelCacheEntry;

Attribute Cat Entry

typedef struct AttrCatEntry {
    unsigned char relName[ATTR_SIZE];
    unsigned char attrName[ATTR_SIZE];
    int attrType;
    int primaryFlag;
    int rootBlock;
    int offset;
} AttrCatEntry;

typedef struct AttrCacheEntry {
    AttrCatEntry attrCatEntry;
    bool dirty;
    RecId recId;
    RecId searchIndex;
    struct AttrCacheEntry *next
} AttrCacheEntry;

Open Relation Table Structure

A relation must have an entry in AttrCache, RelCache, and in Open Relation Table

typedef struct OpenRelTableMetaInfo {
    bool free;
    unsigned char relName[ATTR_SIZE];
} OpenRelTableMetaInfo;