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07-metadata-management.md

File metadata and controls

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Chapter 7: Metadata Management

7.1. TableMgr

  1. Overview

  2. Add metadata/TableMgr.java

  3. Add the following code to App.java

    // 7. Metadata Management
System.out.println("7.1. TableMgr ------------------");
bm = new BufferMgr(fm, lm, 8); // numbuffs: 3 is not enough
tx = new Transaction(fm, lm, bm);
TableMgr tm = new TableMgr(true, tx);
sch = new Schema();
sch.addIntField("A");
sch.addStringField("B", 9);
tm.createTable("MyTable", sch, tx);

layout = tm.getLayout("MyTable", tx);
int size = layout.slotSize();
Schema sch2 = layout.schema();
System.out.println("MyTable has slot size" + size);
System.out.println("Its fields are:");
for (String fldname : sch2.fields()) {
  String type;
  if (sch2.type(fldname) == INTEGER)
    type = "int";
  else {
    int strlen = sch2.length(fldname);
    type = "varchar(" + strlen + ")";
  }

  System.out.println(fldname + ": " + type);
}
tx.commit();

  4. Run

    ./gradlew run

    7.1. TableMgr ------------------
[TableMgr] createTable table: tblcat
[ConcurrencyMgr] starting new sLock on file: tblcat.tbl, blk: -1. ({})
[LockTable] starting slock on blk -1
[LockTable] completed slock on blk -1, status: slock
[TableScan] moveToBlock file: tblcat.tbl, blk: 0
[ConcurrencyMgr] starting new sLock on file: tblcat.tbl, blk: 0. ({[file tblcat.tbl, block -1]=S})
[LockTable] starting slock on blk 0
[LockTable] completed slock on blk 0, status: slock
[TableScan] moveToBlock file: tblcat.tbl, blk: 1
[ConcurrencyMgr] starting new sLock on file: tblcat.tbl, blk: 1. ({[file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S})
[LockTable] starting slock on blk 1
[LockTable] completed slock on blk 1, status: slock
[TableScan] moveToBlock file: tblcat.tbl, blk: 2
[ConcurrencyMgr] starting new sLock on file: tblcat.tbl, blk: 2. ({[file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S})
[LockTable] starting slock on blk 2
[LockTable] completed slock on blk 2, status: slock
[TableScan] moveToBlock file: tblcat.tbl, blk: 3
[ConcurrencyMgr] starting new sLock on file: tblcat.tbl, blk: 3. ({[file tblcat.tbl, block 2]=S, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S})
[LockTable] starting slock on blk 3
[LockTable] completed slock on blk 3, status: slock
[Transaction] setInt to block 3 with offset 252 and val 1
[ConcurrencyMgr] starting new xLock on tblcat.tbl, blk: 3. ({[file tblcat.tbl, block 3]=S, [file tblcat.tbl, block 2]=S, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S})
[LockTable] starting xlock on blk: 3
[LockTable] completed xlock on blk: 3, status: xlock
[Transaction] setString to block 3 with offset 256 and val tblcat
[FileMgr] appending block (size 400) to simpledb.log
[FileMgr] finished appending block. blknum: 27
[Transaction] setInt to block 3 with offset 276 and val 28
[ConcurrencyMgr] starting new sLock on file: fldcat.tbl, blk: -1. ({[file tblcat.tbl, block 3]=X, [file tblcat.tbl, block 2]=S, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S})
[LockTable] starting slock on blk -1
[LockTable] completed slock on blk -1, status: slock
[TableScan] moveToBlock file: fldcat.tbl, blk: 0
[ConcurrencyMgr] starting new sLock on file: fldcat.tbl, blk: 0. ({[file tblcat.tbl, block 3]=X, [file tblcat.tbl, block 2]=S, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S, [file fldcat.tbl, block -1]=S})
[LockTable] starting slock on blk 0
[LockTable] completed slock on blk 0, status: slock
[Transaction] setInt to block 0 with offset 0 and val 1
[ConcurrencyMgr] starting new xLock on fldcat.tbl, blk: 0. ({[file tblcat.tbl, block 3]=X, [file tblcat.tbl, block 2]=S, [file fldcat.tbl, block 0]=S, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S, [file fldcat.tbl, block -1]=S})
[LockTable] starting xlock on blk: 0
[LockTable] completed xlock on blk: 0, status: xlock
[Transaction] setString to block 0 with offset 4 and val tblcat
[Transaction] setString to block 0 with offset 24 and val tblname
[Transaction] setInt to block 0 with offset 44 and val 12
[Transaction] setInt to block 0 with offset 48 and val 16
[Transaction] setInt to block 0 with offset 52 and val 4
[Transaction] setInt to block 0 with offset 56 and val 1
[Transaction] setString to block 0 with offset 60 and val tblcat
[Transaction] setString to block 0 with offset 80 and val slotsize
[FileMgr] appending block (size 400) to simpledb.log
[FileMgr] finished appending block. blknum: 28
[Transaction] setInt to block 0 with offset 100 and val 4
[Transaction] setInt to block 0 with offset 104 and val 0
[Transaction] setInt to block 0 with offset 108 and val 24
[TableMgr] createTable completed table: tblcat
[TableMgr] createTable table: fldcat
[TableScan] moveToBlock file: tblcat.tbl, blk: 0
[TableScan] moveToBlock file: tblcat.tbl, blk: 1
[TableScan] moveToBlock file: tblcat.tbl, blk: 2
[TableScan] moveToBlock file: tblcat.tbl, blk: 3
[Transaction] setInt to block 3 with offset 280 and val 1
[Transaction] setString to block 3 with offset 284 and val fldcat
[Transaction] setInt to block 3 with offset 304 and val 56
[TableScan] moveToBlock file: fldcat.tbl, blk: 0
[Transaction] setInt to block 0 with offset 112 and val 1
[Transaction] setString to block 0 with offset 116 and val fldcat
[Transaction] setString to block 0 with offset 136 and val tblname
[Transaction] setInt to block 0 with offset 156 and val 12
[FileMgr] appending block (size 400) to simpledb.log
[FileMgr] finished appending block. blknum: 29
[Transaction] setInt to block 0 with offset 160 and val 16
[Transaction] setInt to block 0 with offset 164 and val 4
[Transaction] setInt to block 0 with offset 168 and val 1
[Transaction] setString to block 0 with offset 172 and val fldcat
[Transaction] setString to block 0 with offset 192 and val fldname
[Transaction] setInt to block 0 with offset 212 and val 12
[Transaction] setInt to block 0 with offset 216 and val 16
[Transaction] setInt to block 0 with offset 220 and val 24
[Transaction] setInt to block 0 with offset 224 and val 1
[Transaction] setString to block 0 with offset 228 and val fldcat
[FileMgr] appending block (size 400) to simpledb.log
[FileMgr] finished appending block. blknum: 30
[Transaction] setString to block 0 with offset 248 and val type
[Transaction] setInt to block 0 with offset 268 and val 4
[Transaction] setInt to block 0 with offset 272 and val 0
[Transaction] setInt to block 0 with offset 276 and val 44
[Transaction] setInt to block 0 with offset 280 and val 1
[Transaction] setString to block 0 with offset 284 and val fldcat
[Transaction] setString to block 0 with offset 304 and val length
[Transaction] setInt to block 0 with offset 324 and val 4
[Transaction] setInt to block 0 with offset 328 and val 0
[Transaction] setInt to block 0 with offset 332 and val 48
[FileMgr] appending block (size 400) to simpledb.log
[FileMgr] finished appending block. blknum: 31
[Transaction] setInt to block 0 with offset 336 and val 1
[Transaction] setString to block 0 with offset 340 and val fldcat
[Transaction] setString to block 0 with offset 360 and val offset
[Transaction] setInt to block 0 with offset 380 and val 4
[Transaction] setInt to block 0 with offset 384 and val 0
[Transaction] setInt to block 0 with offset 388 and val 52
[TableMgr] createTable completed table: fldcat
[TableMgr] createTable table: MyTable
[TableScan] moveToBlock file: tblcat.tbl, blk: 0
[TableScan] moveToBlock file: tblcat.tbl, blk: 1
[TableScan] moveToBlock file: tblcat.tbl, blk: 2
[TableScan] moveToBlock file: tblcat.tbl, blk: 3
[Transaction] setInt to block 3 with offset 308 and val 1
[Transaction] setString to block 3 with offset 312 and val MyTable
[Transaction] setInt to block 3 with offset 332 and val 21
[TableScan] moveToBlock file: fldcat.tbl, blk: 0
[TableScan] moveToBlock file: fldcat.tbl, blk: 1
[ConcurrencyMgr] starting new sLock on file: fldcat.tbl, blk: 1. ({[file tblcat.tbl, block 3]=X, [file tblcat.tbl, block 2]=S, [file fldcat.tbl, block 0]=X, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S, [file fldcat.tbl, block -1]=S})
[LockTable] starting slock on blk 1
[LockTable] completed slock on blk 1, status: slock
[Transaction] setInt to block 1 with offset 0 and val 1
[ConcurrencyMgr] starting new xLock on fldcat.tbl, blk: 1. ({[file tblcat.tbl, block 3]=X, [file tblcat.tbl, block 2]=S, [file fldcat.tbl, block 0]=X, [file fldcat.tbl, block 1]=S, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S, [file fldcat.tbl, block -1]=S})
[LockTable] starting xlock on blk: 1
[LockTable] completed xlock on blk: 1, status: xlock
[FileMgr] appending block (size 400) to simpledb.log
[FileMgr] finished appending block. blknum: 32
[Transaction] setString to block 1 with offset 4 and val MyTable
[Transaction] setString to block 1 with offset 24 and val A
[Transaction] setInt to block 1 with offset 44 and val 4
[Transaction] setInt to block 1 with offset 48 and val 0
[Transaction] setInt to block 1 with offset 52 and val 4
[Transaction] setInt to block 1 with offset 56 and val 1
[Transaction] setString to block 1 with offset 60 and val MyTable
[Transaction] setString to block 1 with offset 80 and val B
[Transaction] setInt to block 1 with offset 100 and val 12
[Transaction] setInt to block 1 with offset 104 and val 9
[FileMgr] appending block (size 400) to simpledb.log
[FileMgr] finished appending block. blknum: 33
[Transaction] setInt to block 1 with offset 108 and val 8
[TableMgr] createTable completed table: MyTable
[TableScan] moveToBlock file: tblcat.tbl, blk: 0
[TableScan] moveToBlock file: fldcat.tbl, blk: 0
[TableScan] moveToBlock file: fldcat.tbl, blk: 1
MyTable has slot size21
Its fields are:
A: int
B: varchar(9)
transaction 7 committed
[ConcurrencyMgr] starting release: {[file tblcat.tbl, block 3]=X, [file tblcat.tbl, block 2]=S, [file fldcat.tbl, block 0]=X, [file fldcat.tbl, block 1]=X, [file tblcat.tbl, block 1]=S, [file tblcat.tbl, block 0]=S, [file tblcat.tbl, block -1]=S, [file fldcat.tbl, block -1]=S}
[LockTable] starting unlock on blk: 3
[LockTable] completed unlock on blk: 3, status: no lock
[LockTable] starting unlock on blk: 2
[LockTable] completed unlock on blk: 2, status: no lock
[LockTable] starting unlock on blk: 0
[LockTable] completed unlock on blk: 0, status: no lock
[LockTable] starting unlock on blk: 1
[LockTable] completed unlock on blk: 1, status: no lock
[LockTable] starting unlock on blk: 1
[LockTable] completed unlock on blk: 1, status: no lock
[LockTable] starting unlock on blk: 0
[LockTable] completed unlock on blk: 0, status: no lock
[LockTable] starting unlock on blk: -1
[LockTable] completed unlock on blk: -1, status: no lock
[LockTable] starting unlock on blk: -1
[LockTable] completed unlock on blk: -1, status: no lock
[ConcurrencyMgr] completed release: {}

  5. Add mockito to app/build.gradle.kts

    dependencies {
+    // mockito
+    testImplementation("org.mockito:mockito-core:3.6.0")
+
+    // mockito JUnit 5 Extension
+    testImplementation("org.mockito:mockito-junit-jupiter:3.6.0")
}

  6. Add Test

    Table Catalog:

    tablename slotsize
    tblcat 28
    fldcat 56

    Field Catalog: |tblname|fldname|type|length|offset| |---|---|---|---|---|---| |tblcat|tblname|1|16|4| |tblcat|slotsize|0|0|24| |fldcat|tblname|1|16|4| |fldcat|fldname|1|16|24| |fldcat|type|0|0|44| |fldcat|length|0|0|48| |fldcat|offset|0|0|52|

    package simpledb.metadata;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.mockito.Mockito.when;

import java.io.File;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;

import simpledb.buffer.BufferMgr;
import simpledb.file.BlockId;
import simpledb.file.FileMgr;
import simpledb.log.LogMgr;
import simpledb.record.Layout;
import simpledb.record.RecordPage;
import simpledb.record.Schema;
import simpledb.tx.Transaction;

@ExtendWith(MockitoExtension.class)
public class TableMgrTest {
  @Mock
  private Transaction tx;

  @Test
  public void testTblCatLayout() throws Exception {
    when(tx.getInt(new BlockId("tblcat.tbl", 0), 0)).thenReturn(RecordPage.USED); // flag for record 0
    when(tx.getString(new BlockId("tblcat.tbl", 0), 4)).thenReturn("tblcat"); // value for record 0
    when(tx.getInt(new BlockId("tblcat.tbl", 0), 24)).thenReturn(28); // flag for record 1
    when(tx.size("tblcat.tbl")).thenReturn(10); // 10 blocks in tbl1.tbl

    when(tx.getInt(new BlockId("fldcat.tbl", 0), 0)).thenReturn(RecordPage.USED); // flag for record 0
    when(tx.getString(new BlockId("fldcat.tbl", 0), 4)).thenReturn("tblcat"); // tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 24)).thenReturn("tblname"); // fldname
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 44)).thenReturn(1); // type
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 48)).thenReturn(16); // length
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 52)).thenReturn(4); // offset
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56)).thenReturn(RecordPage.USED); // flag for record 0
    when(tx.getString(new BlockId("fldcat.tbl", 0), 56 + 4)).thenReturn("tblcat"); // tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 56 + 24)).thenReturn("slotsize"); // fldname
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56 + 44)).thenReturn(0); // type
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56 + 48)).thenReturn(0); // length
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56 + 52)).thenReturn(24); // offset
    when(tx.size("fldcat.tbl")).thenReturn(10); // 10 blocks in tbl1.tbl
    when(tx.blockSize()).thenReturn(400);
    TableMgr tableMgr = new TableMgr(false, tx);

    Layout layout = tableMgr.getLayout(TableMgr.TBL_CAT_TABLE, tx);
    assertEquals(4, layout.offset(TableMgr.TBL_CAT_FIELD_TABLE_NAME));
    assertEquals(24, layout.offset(TableMgr.TBL_CAT_FIELD_SLOTSIZE));
    assertEquals(28, layout.slotSize());
  }

  @Test
  public void testFldCatLayout() throws Exception {
    // tblcat.tbl
    when(tx.getInt(new BlockId("tblcat.tbl", 0), 0)).thenReturn(RecordPage.USED); // flag for record 1
    when(tx.getString(new BlockId("tblcat.tbl", 0), 4)).thenReturn("fldcat"); // tblname for record 1
    when(tx.getInt(new BlockId("tblcat.tbl", 0), 24)).thenReturn(56); // fldcat's slotsize
    when(tx.size("tblcat.tbl")).thenReturn(10); // 10 blocks in tbl1.tbl

    // fldcat.tbl
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 0)).thenReturn(RecordPage.USED); // flag for fldcat.tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 4)).thenReturn("fldcat"); // tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 24)).thenReturn("tblname"); // fldname
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 44)).thenReturn(1); // type
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 48)).thenReturn(16); // length
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 52)).thenReturn(4); // offset
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56)).thenReturn(RecordPage.USED); // flag for fldcat.fldname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 56 + 4)).thenReturn("fldcat"); // tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 56 + 24)).thenReturn("fldname"); // fldname
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56 + 44)).thenReturn(1); // type
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56 + 48)).thenReturn(16); // length
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 56 + 52)).thenReturn(24); // offset
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 112)).thenReturn(RecordPage.USED); // flag for fldcat.type
    when(tx.getString(new BlockId("fldcat.tbl", 0), 112 + 4)).thenReturn("fldcat"); // tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 112 + 24)).thenReturn("type"); // fldname
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 112 + 44)).thenReturn(0); // type
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 112 + 48)).thenReturn(0); // length
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 112 + 52)).thenReturn(44); // offset
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 168)).thenReturn(RecordPage.USED); // flag for fldcat.length
    when(tx.getString(new BlockId("fldcat.tbl", 0), 168 + 4)).thenReturn("fldcat"); // tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 168 + 24)).thenReturn("length"); // fldname
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 168 + 44)).thenReturn(0); // type
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 168 + 48)).thenReturn(0); // length
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 168 + 52)).thenReturn(48); // offset
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 224)).thenReturn(RecordPage.USED); // flag for fldcat.offset
    when(tx.getString(new BlockId("fldcat.tbl", 0), 224 + 4)).thenReturn("fldcat"); // tblname
    when(tx.getString(new BlockId("fldcat.tbl", 0), 224 + 24)).thenReturn("offset"); // fldname
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 224 + 44)).thenReturn(0); // type
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 224 + 48)).thenReturn(0); // length
    when(tx.getInt(new BlockId("fldcat.tbl", 0), 224 + 52)).thenReturn(52); // offset
    when(tx.size("fldcat.tbl")).thenReturn(10); // 10 blocks in tbl1.tbl
    when(tx.blockSize()).thenReturn(400);
    TableMgr tableMgr = new TableMgr(false, tx);

    Layout layout = tableMgr.getLayout(TableMgr.FLD_CAT_TABLE, tx);
    assertEquals(4, layout.offset(TableMgr.FLD_CAT_FIELD_TABLE_NAME));
    assertEquals(24, layout.offset(TableMgr.FLD_CAT_FIELD_FEILD_NAME));
    assertEquals(44, layout.offset(TableMgr.FLD_CAT_FIELD_TYPE));
    assertEquals(48, layout.offset(TableMgr.FLD_CAT_FIELD_LENGTH));
    assertEquals(52, layout.offset(TableMgr.FLD_CAT_FIELD_OFFSET));
    assertEquals(56, layout.slotSize());
  }

  @Test
  public void testCreateTableGetLayout() throws Exception {
    File dbDirectory = new File("datadir");
    FileMgr fm = new FileMgr(dbDirectory, 400);
    LogMgr lm = new LogMgr(fm, "simpledb.log");
    BufferMgr bm = new BufferMgr(fm, lm, 8);
    Transaction tx = new Transaction(fm, lm, bm);
    TableMgr tableMgr = new TableMgr(true, tx);

    Schema sch = new Schema();
    sch.addStringField("name", 50);
    sch.addIntField("count");
    tableMgr.createTable("test_table", sch, tx);

    Layout layout = tableMgr.getLayout("test_table", tx); // read via TableScan (from the file)

    assertEquals(2, layout.schema().fields().size());
    assertEquals(4, layout.offset("name"));
    // 4 bytes for the empty/inuse flag, 54 bytes for name string (4 bytes for the
    // byte
    // length and 50 bytes for bytes themselves)
    assertEquals(4 + 54, layout.offset("count"));
  }
}

  7. Run test

    ./gradlew test

7.2. ViewMgr

  1. metadata/ViewMgr.java

    package simpledb.metadata;

import simpledb.record.Layout;
import simpledb.record.Schema;
import simpledb.record.TableScan;
import simpledb.tx.Transaction;

public class ViewMgr {
  private static final int MAX_VIEW_DEF = 100;
  private static final String VIEW_CAT_TABLE = "viewcat";
  private static final String VIEW_CAT_FIELD_NAME = "viewname";
  private static final String VIEW_CAT_FIELD_DEF = "viewdef";

  TableMgr tblMgr;

  public ViewMgr(boolean isNew, TableMgr tblMgr, Transaction tx) {
    this.tblMgr = tblMgr;
    if (isNew) {
      Schema sch = new Schema();
      sch.addStringField(VIEW_CAT_FIELD_NAME, TableMgr.MAX_NAME);
      sch.addStringField(VIEW_CAT_FIELD_DEF, MAX_VIEW_DEF);
      tblMgr.createTable(VIEW_CAT_TABLE, sch, tx);
    }
  }

  public void createView(String vname, String vdef, Transaction tx) {
    Layout layout = tblMgr.getLayout(VIEW_CAT_TABLE, tx);
    TableScan ts = new TableScan(tx, VIEW_CAT_TABLE, layout);
    ts.insert();
    ts.setString(VIEW_CAT_FIELD_NAME, vname);
    ts.setString(VIEW_CAT_FIELD_DEF, vdef);
    ts.close();
  }

  public String getViewDef(String vname, Transaction tx) {
    String result = null;
    Layout layout = tblMgr.getLayout(VIEW_CAT_TABLE, tx);
    TableScan ts = new TableScan(tx, VIEW_CAT_TABLE, layout);
    while (ts.next()) {
      if (ts.getString(VIEW_CAT_FIELD_NAME).equals(vname)) {
        result = ts.getString(VIEW_CAT_FIELD_DEF);
        break;
      }
    }
    ts.close();
    return result;
  }
}

7.3. StatMgr

  1. metadata/StatInfo.java

    package simpledb.metadata;

/*
 * StatInfo stores three pieces of information of a table:
 * 1. the number of blocks
 * 2. the number of records
 * 3. the number of distinct values for each fields (TODO)
 */
public class StatInfo {
  private int numBlocks;
  private int numRecs;

  public StatInfo(int numBlocks, int numRecs) {
    this.numBlocks = numBlocks;
    this.numRecs = numRecs;
  }

  public int blockAccessed() {
    return numBlocks;
  }

  public int recordsOutput() {
    return numRecs;
  }

  /*
   * Return the estimated number of distinct values for the specified fields.
   * Current implementation always returns one thirds of the number of records.
   */
  public int distinctValues(String fldname) {
    // TODO: implement real logic to calculate
    return 1 + (numRecs / 3);
  }
}

  2. metadata/StatMgr.java

    package simpledb.metadata;

import java.util.HashMap;
import java.util.Map;

import simpledb.record.Layout;
import simpledb.record.TableScan;
import simpledb.tx.Transaction;

/*
 * Stat manager stores statistical information of each table
 * in tablestats (in memory) not in the database.
 * It calculates the stats on system startup and every 100 retrievals.
 */
public class StatMgr {
  private TableMgr tblMgr;
  // Store stats for each table
  private Map<String, StatInfo> tablestats;
  // used to determine if stats should be updated
  private int numcalls;

  public StatMgr(TableMgr tblMgr, Transaction tx) {
    this.tblMgr = tblMgr;
    refreshStats(tx);
  }

  public synchronized StatInfo getStatInfo(String tblname, Layout layout, Transaction tx) {
    numcalls++;
    if (numcalls > 100)
      refreshStats(tx);

    StatInfo si = tablestats.get(tblname);
    if (si == null) {
      si = calcTableStats(tblname, layout, tx);
      tablestats.put(tblname, si);
    }
    return si;
  }

  private synchronized void refreshStats(Transaction tx) {
    tablestats = new HashMap<>();
    numcalls = 0;
    Layout tcatlayout = tblMgr.getLayout(tblMgr.TBL_CAT_TABLE, tx);
    TableScan tcat = new TableScan(tx, TableMgr.TBL_CAT_TABLE, tcatlayout);
    while (tcat.next()) {
      String tblname = tcat.getString(tblMgr.TBL_CAT_FIELD_TABLE_NAME);
      Layout layout = tblMgr.getLayout(tblname, tx);
      StatInfo si = calcTableStats(tblname, layout, tx);
      tablestats.put(tblname, si);
    }
    tcat.close();
  }

  private synchronized StatInfo calcTableStats(String tblname, Layout layout, Transaction tx) {
    int numRecs = 0;
    int numBlocks = 0;
    TableScan ts = new TableScan(tx, tblname, layout);
    while (ts.next()) {
      numRecs++;
      numBlocks = ts.getRid().blockNumber() + 1;
    }
    ts.close();
    return new StatInfo(numBlocks, numRecs);
  }
}

7.4. IndexMgr

  1. Add Index interface index/Index.java and DummyIndex that implements the interface index/DummyIndex.java

    package simpledb.index;

import simpledb.query.Constant;
import simpledb.record.RID;

public interface Index {

  /*
  * Positions the index before the first record
  * having the specified search key
  */
  public void beforeFirst(Constant searchkey);

  /*
  * Moves the index to the next record having
  * the search key specified in the beforeFirst method
  */
  public boolean next();

  /*
  * Returns the dataRID value stored in the current index record
  */
  public RID getDataRid();

  /*
  * Inserts an index record having the specified dataval and dataRID values.
  */
  public void insert(Constant dataval, RID datarid);

  /*
  * Deletes the index record having the specified dataval and dataRID values.
  */
  public void delete(Constant dataval, RID datarid);

  /*
  * Closes the index.
  */
  public void close();

}
    package simpledb.index;

import simpledb.query.Constant;
import simpledb.record.Layout;
import simpledb.record.RID;
import simpledb.tx.Transaction;

public class DummyIndex implements Index {

  public DummyIndex(Transaction tx, String idxname, Layout idxLayout) {
  }

  public static int searchCost(int numBlocks, int rpb) {
    // TODO: implement later
    return 1;
  }

  @Override
  public void beforeFirst(Constant searchkey) {
    // TODO Auto-generated method stub

  }

  @Override
  public boolean next() {
    // TODO Auto-generated method stub
    return false;
  }

  @Override
  public RID getDataRid() {
    // TODO Auto-generated method stub
    return null;
  }

  @Override
  public void insert(Constant dataval, RID datarid) {
    // TODO Auto-generated method stub

  }

  @Override
  public void delete(Constant dataval, RID datarid) {
    // TODO Auto-generated method stub

  }

  @Override
  public void close() {
    // TODO Auto-generated method stub

  }

}

  2. metadata/IndexInfo.java

    package simpledb.metadata;

import static java.sql.Types.INTEGER;

import simpledb.index.DummyIndex;
import simpledb.index.Index;
import simpledb.record.Layout;
import simpledb.record.Schema;
import simpledb.tx.Transaction;

public class IndexInfo {
  private String idxname;
  private String fldname;
  private Transaction tx;
  private Schema tblSchema;
  private Layout idxLayout;
  private StatInfo si;

  public IndexInfo(String idxname, String fldname, Schema tblSchema, Transaction tx, StatInfo si) {
    this.idxname = idxname;
    this.fldname = fldname;
    this.tx = tx;
    this.tblSchema = tblSchema;
    this.idxLayout = createIdxLayout();
    this.si = si;
  }

  public Index open() {
    // TODO: replace with a real Index class
    return new DummyIndex(tx, idxname, idxLayout);
  }

  public int blocksAccessed() {
    int rpb = tx.blockSize() / idxLayout.slotSize();
    int numBlocks = si.recordsOutput() / rpb;
    return DummyIndex.searchCost(numBlocks, rpb);
  }

  /*
  * Return the estimated number of records having a search key.
  * The number of distinct values of the indexed fields.
  * This estimate will be very poor if not evenly distributed.
  */
  public int recordsOutput() {
    return si.recordsOutput() / si.distinctValues(fldname);
  }

  /*
  * Return the distinct values for a specified field or 1 for the indexed field
  */
  public int distinctValues(String fname) {
    return fldname.equals(fname) ? 1 : si.distinctValues(fldname);
  }

  /*
  * Return the layout of the index records.
  * The schema consists of
  * 1. RID (the block number and record id)
  * 2. dataval: the type is determined based on the fldname
  */
  private Layout createIdxLayout() {
    Schema sch = new Schema();
    sch.addIntField("block");
    sch.addIntField("id");
    if (tblSchema.type(fldname) == INTEGER)
      sch.addIntField("dataval");
    else {
      int fldlen = tblSchema.length(fldname);
      sch.addStringField("dataval", fldlen);
    }
    return new Layout(sch);
  }
}

  3. metadata/IndexMgr.java

    package simpledb.metadata;

import static simpledb.metadata.TableMgr.MAX_NAME;

import java.util.HashMap;
import java.util.Map;

import simpledb.record.Layout;
import simpledb.record.Schema;
import simpledb.record.TableScan;
import simpledb.tx.Transaction;

public class IndexMgr {
  private Layout layout;
  private TableMgr tblmgr;
  private StatMgr statmgr;
  private static final String IDX_CAT_TABLE_NAME = "idxcat";
  private static final String IDX_CAT_FIELD_INDEX_NAME = "indexname";
  private static final String IDX_CAT_FIELD_TABLE_NAME = "tablename";
  private static final String IDX_CAT_FIELD_FIELD_NAME = "fieldname";

  public IndexMgr(boolean isnew, TableMgr tblmgr, StatMgr statmgr, Transaction tx) {
    if (isnew) {
      Schema sch = new Schema();
      sch.addStringField(IDX_CAT_FIELD_INDEX_NAME, MAX_NAME);
      sch.addStringField(IDX_CAT_FIELD_TABLE_NAME, MAX_NAME);
      sch.addStringField(IDX_CAT_FIELD_FIELD_NAME, MAX_NAME);
      tblmgr.createTable(IDX_CAT_TABLE_NAME, sch, tx);
    }
    this.tblmgr = tblmgr;
    this.statmgr = statmgr;
    layout = tblmgr.getLayout(IDX_CAT_TABLE_NAME, tx);
  }

  public void creatIndex(String idxname, String tblname, String fldname, Transaction tx) {
    TableScan ts = new TableScan(tx, IDX_CAT_TABLE_NAME, layout);
    ts.insert();
    ts.setString(IDX_CAT_FIELD_INDEX_NAME, idxname);
    ts.setString(IDX_CAT_FIELD_TABLE_NAME, tblname);
    ts.setString(IDX_CAT_FIELD_FIELD_NAME, fldname);
    ts.close();
  }

  public Map<String, IndexInfo> getIndexInfo(String tblname, Transaction tx) {
    Map<String, IndexInfo> result = new HashMap<>();
    TableScan ts = new TableScan(tx, IDX_CAT_TABLE_NAME, layout);
    while (ts.next()) {
      if (ts.getString(IDX_CAT_FIELD_TABLE_NAME).equals(tblname)) {
        String idxname = ts.getString(IDX_CAT_FIELD_INDEX_NAME);
        String fldname = ts.getString(IDX_CAT_FIELD_FIELD_NAME);
        Layout tblLayout = tblmgr.getLayout(tblname, tx);
        StatInfo tblsi = statmgr.getStatInfo(tblname, tblLayout, tx);
        IndexInfo ii = new IndexInfo(idxname, fldname, tblLayout.schema(), tx, tblsi);
        result.put(fldname, ii);
      }
    }
    return result;
  }
}

7.5. MetadataMgr

  1. Add metadata/MetadataMgr.java

    package simpledb.metadata;

import java.util.Map;

import simpledb.record.Layout;
import simpledb.record.Schema;
import simpledb.tx.Transaction;

/*
* Metadata Manager holds the four managers
* 1. table manager
* 2. view manager
* 3. stat manager
* 4. index manager
*/
public class MetadataMgr {
  private static TableMgr tblmgr;
  private static ViewMgr viewmgr;
  private static StatMgr statmgr;
  private static IndexMgr idxmgr;

  public MetadataMgr(boolean isnew, Transaction tx) {
    tblmgr = new TableMgr(isnew, tx);
    viewmgr = new ViewMgr(isnew, tblmgr, tx);
    statmgr = new StatMgr(tblmgr, tx);
    idxmgr = new IndexMgr(isnew, tblmgr, statmgr, tx);
  }

  public void createTable(String tblname, Schema sch, Transaction tx) {
    tblmgr.createTable(tblname, sch, tx);
  }

  public Layout getLayout(String tblname, Transaction tx) {
    return tblmgr.getLayout(tblname, tx);
  }

  public void createView(String viewname, String viewdef, Transaction tx) {
    viewmgr.createView(viewname, viewdef, tx);
  }

  public String getViewDef(String viewname, Transaction tx) {
    return viewmgr.getViewDef(viewname, tx);
  }

  public void createIndex(String idxname, String tblname, String fldname, Transaction tx) {
    idxmgr.creatIndex(idxname, tblname, fldname, tx);
  }

  public Map<String, IndexInfo> getIndexInfo(String tblname, Transaction tx) {
    return idxmgr.getIndexInfo(tblname, tx);
  }

  public StatInfo getStatInfo(String tblname, Layout layout, Transaction tx) {
    return statmgr.getStatInfo(tblname, layout, tx);
  }
}

  2. Add the following code to App.java

    System.out.println("7.5. MetadataMgr ----------------");
tx = new Transaction(fm, lm, bm);
MetadataMgr metadataMgr = new MetadataMgr(true, tx);
sch = new Schema();
sch.addStringField("name", 50);
sch.addIntField("count");

// Create Table
metadataMgr.createTable("test_table", sch, tx);

layout = metadataMgr.getLayout("test_table", tx); // read via TableScan (from the file)
System.out.println("layout.schema.fields.size (expected: 2): " + layout.schema().fields().size());
System.out.println("layout.offset for name (expected: 4): " + layout.offset("name"));
System.out.println("layout.offset for name (expected: 54): " + layout.offset("count"));

metadataMgr.createView("test_view", "view def", tx);
String viewdef = metadataMgr.getViewDef("test_view", tx); // read via TableScan (from the file)
System.out.println("view def: " + viewdef);
tx.commit();

  3. ToDO: test with test codes

    package simpledb.metadata;

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.io.File;
import java.util.Map;

import org.junit.jupiter.api.Test;

import simpledb.buffer.BufferMgr;
import simpledb.file.FileMgr;
import simpledb.log.LogMgr;
import simpledb.record.Layout;
import simpledb.record.Schema;
import simpledb.tx.Transaction;

public class MetadataMgrTest {
  @Test
  public void testMetadataMgrTest() throws Exception {
    File dbDirectory = new File("datadir");
    FileMgr fm = new FileMgr(dbDirectory, 400);
    LogMgr lm = new LogMgr(fm, "simpledb.log");
    BufferMgr bm = new BufferMgr(fm, lm, 8);
    Transaction tx = new Transaction(fm, lm, bm);
    MetadataMgr metadataMgr = new MetadataMgr(true, tx);

    Schema sch = new Schema();
    sch.addStringField("name", 50);
    sch.addIntField("count");

    // Create Table
    metadataMgr.createTable("test_table", sch, tx);

    Layout layout = metadataMgr.getLayout("test_table", tx); // read via TableScan (from the file)
    assertEquals(2, layout.schema().fields().size());
    assertEquals(4, layout.offset("name"));
    // 4 bytes for the empty/inuse flag, 54 bytes for name string (4 bytes for the
    // byte
    // length and 50 bytes for bytes themselves)
    //
    assertEquals(4 + 54, layout.offset("count"));

    // Create View
    metadataMgr.createView("test_view", "view def", tx);

    String viewdef = metadataMgr.getViewDef("test_view", tx); // read via TableScan (from the file)
    assertEquals("view def", viewdef);
  }
}