Analyzing B-Tree Indexes
CREATE TABLE index_log (
owner VARCHAR2(30),
index_name VARCHAR2(30),
last_inspected DATE,
leaf_blocks NUMBER,
target_size NUMBER,
idx_layout CLOB);
ALTER TABLE index_log ADD CONSTRAINT pk_index_log PRIMARY KEY (owner,index_name);
CREATE TABLE index_hist (
owner VARCHAR2(30),
index_name VARCHAR2(30),
inspected_date DATE,
leaf_blocks NUMBER,
target_size NUMBER,
idx_layout VARCHAR2(4000));
ALTER TABLE index_hist ADD CONSTRAINT pk_index_hist PRIMARY KEY (owner,index_name,inspected_date);
--
-- Variables:
-- vMinBlks: Specifies the minimum number of leaf blocks for scanning the index
-- Indexes below this number will not be scanned/reported on
-- vScaleFactor: The scaling factor, defines the threshold of the estimated leaf block count
-- to be smaller than the supplied fraction of the current size.
-- vTargetUse : Supplied percentage utilisation. For example 90% equates to the default pctfree 10
-- vHistRet : Defines the number of records to keep in the INDEX_HIST table for each index entry
--
CREATE OR REPLACE PACKAGE index_util AUTHID CURRENT_USER IS
vMinBlks CONSTANT POSITIVE := 1000;
vScaleFactor CONSTANT NUMBER := 0.6;
vTargetUse CONSTANT POSITIVE := 90; -- equates to pctfree 10
vHistRet CONSTANT POSITIVE := 10; -- (#) records to keep in index_hist
procedure inspect_schema (aSchemaName IN VARCHAR2);
procedure inspect_index (aIndexOwner IN VARCHAR2, aIndexName IN VARCHAR2, aTableOwner IN VARCHAR2, aTableName IN VARCHAR2, aLeafBlocks IN NUMBER);
END index_util;
/
CREATE OR REPLACE PACKAGE BODY index_util IS
procedure inspect_schema (aSchemaName IN VARCHAR2) IS
begin
FOR r IN (select table_owner, table_name, owner index_owner, index_name, leaf_blocks
from dba_indexes
where owner = upper(aSchemaname)
and index_type in ('NORMAL','NORMAL/REV','FUNCTION-BASED NORMAL')
and partitioned = 'NO'
and temporary = 'N'
and dropped = 'NO'
and status = 'VALID'
and last_analyzed is not null
order by owner, table_name, index_name) LOOP
IF r.leaf_blocks > vMinBlks THEN
inspect_index (r.index_owner, r.index_name, r.table_owner, r.table_name, r.leaf_blocks);
END IF;
END LOOP;
commit;
end inspect_schema;
procedure inspect_index (aIndexOwner IN VARCHAR2, aIndexName IN VARCHAR2, aTableOwner IN VARCHAR2, aTableName IN VARCHAR2, aLeafBlocks IN NUMBER) IS
vLeafEstimate number;
vBlockSize number;
vOverhead number := 192; -- leaf block "lost" space in index_stats
vIdxObjID number;
vSqlStr VARCHAR2(4000);
vIndxLyt CLOB;
vCnt number := 0;
TYPE IdxRec IS RECORD (rows_per_block number, cnt_blocks number);
TYPE IdxTab IS TABLE OF IdxRec;
l_data IdxTab;
begin
select a.block_size into vBlockSize from dba_tablespaces a,dba_indexes b where b.index_name=aIndexName and b.owner=aIndexOwner and a.tablespacE_name=b.tablespace_name;
select round (100 / vTargetUse * -- assumed packing efficiency
(ind.num_rows * (tab.rowid_length + ind.uniq_ind + 4) + sum((tc.avg_col_len) * (tab.num_rows) ) -- column data bytes
) / (vBlockSize - vOverhead)
) index_leaf_estimate
into vLeafEstimate
from (select /*+ no_merge */ table_name, num_rows, decode(partitioned,'YES',10,6) rowid_length
from dba_tables
where table_name = aTableName
and owner = aTableOwner) tab,
(select /*+ no_merge */ index_name, index_type, num_rows, decode(uniqueness,'UNIQUE',0,1) uniq_ind
from dba_indexes
where table_owner = aTableOwner
and table_name = aTableName
and owner = aIndexOwner
and index_name = aIndexName) ind,
(select /*+ no_merge */ column_name
from dba_ind_columns
where table_owner = aTableOwner
and table_name = aTableName
and index_owner = aIndexOwner
and index_name = aIndexName) ic,
(select /*+ no_merge */ column_name, avg_col_len
from dba_tab_cols
where owner = aTableOwner
and table_name = aTableName) tc
where tc.column_name = ic.column_name
group by ind.num_rows, ind.uniq_ind, tab.rowid_length;
IF vLeafEstimate < vScaleFactor * aLeafBlocks THEN
select object_id into vIdxObjID
from dba_objects
where owner = aIndexOwner
and object_name = aIndexName;
vSqlStr := 'SELECT rows_per_block, count(*) blocks FROM (SELECT /*+ cursor_sharing_exact ' ||
'dynamic_sampling(0) no_monitoring no_expand index_ffs(' || aTableName ||
',' || aIndexName || ') noparallel_index(' || aTableName ||
',' || aIndexName || ') */ sys_op_lbid(' || vIdxObjID ||
', ''L'', ' || aTableName || '.rowid) block_id, ' ||
'COUNT(*) rows_per_block FROM ' || aTableOwner || '.' || aTableName || ' GROUP BY sys_op_lbid(' ||
vIdxObjID || ', ''L'', ' || aTableName || '.rowid)) group by rows_per_block order by rows_per_block';
execute immediate vSqlStr BULK COLLECT INTO l_data;
vIndxLyt := '';
FOR i IN l_data.FIRST..l_data.LAST LOOP
vIndxLyt := vIndxLyt || l_data(i).rows_per_block || ' - ' || l_data(i).cnt_blocks || chr(10);
END LOOP;
select count(*) into vCnt from index_log where owner = aIndexOwner and index_name = aIndexName;
IF vCnt = 0
THEN insert into index_log values (aIndexOwner, aIndexName, sysdate, aLeafBlocks, round(vLeafEstimate,2), vIndxLyt);
ELSE vCnt := 0;
select count(*) into vCnt from index_hist where owner = aIndexOwner and index_name = aIndexName;
IF vCnt >= vHistRet THEN
delete from index_hist
where owner = aIndexOwner
and index_name = aIndexName
and inspected_date = (select MIN(inspected_date)
from index_hist
where owner = aIndexOwner
and index_name = aIndexName);
END IF;
insert into index_hist select * from index_log where owner = aIndexOwner and index_name = aIndexName;
update index_log
set last_inspected = sysdate,
leaf_blocks = aLeafBlocks,
target_size = round(vLeafEstimate,2),
idx_layout = vIndxLyt
where owner = aIndexOwner and index_name = aIndexName;
END IF;
END IF;
END inspect_index;
END index_util;
/
