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From abr...@apache.org
Subject svn commit: r627836 - /db/derby/code/trunk/java/engine/org/apache/derby/impl/sql/execute/CreateIndexConstantAction.java
Date Thu, 14 Feb 2008 18:42:32 GMT
Author: abrown
Date: Thu Feb 14 10:42:24 2008
New Revision: 627836

URL: http://svn.apache.org/viewvc?rev=627836&view=rev
Log:
DERBY-3299 (incremental: Changes/additions to CreateIndexConstantAction.java
so that it can support the creation of "replacement" conglomerates, which
will be necessary when the physical conglomerate for an index has been
dropped but the index descriptor still exists.  This can happen if multiple
indexes share a physical conglomerate but then the conglomerate is dropped
as part of "drop index" processing for one of the indexes. (Note that
"indexes" here includes indexes which were created to back constraints).
In that case we'll need to create a new "replacement" physical conglomerate
to support the existing descriptor.

Modified:
    db/derby/code/trunk/java/engine/org/apache/derby/impl/sql/execute/CreateIndexConstantAction.java

Modified: db/derby/code/trunk/java/engine/org/apache/derby/impl/sql/execute/CreateIndexConstantAction.java
URL: http://svn.apache.org/viewvc/db/derby/code/trunk/java/engine/org/apache/derby/impl/sql/execute/CreateIndexConstantAction.java?rev=627836&r1=627835&r2=627836&view=diff
==============================================================================
--- db/derby/code/trunk/java/engine/org/apache/derby/impl/sql/execute/CreateIndexConstantAction.java
(original)
+++ db/derby/code/trunk/java/engine/org/apache/derby/impl/sql/execute/CreateIndexConstantAction.java
Thu Feb 14 10:42:24 2008
@@ -85,6 +85,26 @@
 
 	private ExecRow indexTemplateRow;
 
+	/** Conglomerate number for the conglomerate created by this
+	 * constant action; -1L if this constant action has not been
+	 * executed.  If this constant action doesn't actually create
+	 * a new conglomerate--which can happen if it finds an existing
+	 * conglomerate that satisfies all of the criteria--then this
+	 * field will hold the conglomerate number of whatever existing
+	 * conglomerate was found.
+	 */
+	private long conglomId;
+
+	/** Conglomerate number of the physical conglomerate that we
+	 * will "replace" using this constant action.  That is, if
+	 * the purpose of this constant action is to create a new physical
+	 * conglomerate to replace a dropped physical conglomerate, then
+	 * this field holds the conglomerate number of the dropped physical
+	 * conglomerate. If -1L then we are not replacing a conglomerate,
+	 * we're simply creating a new index (and backing physical
+	 * conglomerate) as normal.
+	 */
+	private long droppedConglomNum;
 
 	// CONSTRUCTORS
 	/**
@@ -126,6 +146,73 @@
 		this.isConstraint = isConstraint;
 		this.conglomerateUUID = conglomerateUUID;
 		this.properties = properties;
+		this.conglomId = -1L;
+		this.droppedConglomNum = -1L;
+	}
+
+	/**
+	 * Make a ConstantAction that creates a new physical conglomerate
+	 * based on index information stored in the received descriptors.
+	 * Assumption is that the received ConglomerateDescriptor is still
+	 * valid (meaning it has corresponding entries in the system tables
+	 * and it describes some constraint/index that has _not_ been
+	 * dropped--though the physical conglomerate underneath has).
+	 *
+	 * This constructor is used in cases where the physical conglomerate
+	 * for an index has been dropped but the index still exists. That
+	 * can happen if multiple indexes share a physical conglomerate but
+	 * then the conglomerate is dropped as part of "drop index" processing
+	 * for one of the indexes. (Note that "indexes" here includes indexes
+	 * which were created to back constraints.) In that case we have to
+	 * create a new conglomerate to satisfy the remaining sharing indexes,
+	 * so that's what we're here for.  See ConglomerateDescriptor.drop()
+	 * for details on when that is necessary.
+	 */
+	CreateIndexConstantAction(ConglomerateDescriptor srcCD,
+		TableDescriptor td, Properties properties)
+	{
+		super(td.getUUID(),
+			srcCD.getConglomerateName(), td.getName(), td.getSchemaName());
+
+		this.forCreateTable = false;
+
+		/* We get here when a conglomerate has been dropped and we
+		 * need to create (or find) another one to fill its place.
+		 * At this point the received conglomerate descriptor still
+		 * references the old (dropped) conglomerate, so we can
+		 * pull the conglomerate number from there.
+		 */
+		this.droppedConglomNum = srcCD.getConglomerateNumber();
+
+		/* Plug in the rest of the information from the received
+		 * descriptors.
+		 */
+		IndexRowGenerator irg = srcCD.getIndexDescriptor();
+		this.unique = irg.isUnique();
+		this.indexType = irg.indexType();
+		this.columnNames = srcCD.getColumnNames();
+		this.isAscending = irg.isAscending();
+		this.isConstraint = srcCD.isConstraint();
+		this.conglomerateUUID = srcCD.getUUID();
+		this.properties = properties;
+		this.conglomId = -1L;
+
+		/* The ConglomerateDescriptor may not know the names of
+		 * the columns it includes.  If that's true (which seems
+		 * to be the more common case) then we have to build the
+		 * list of ColumnNames ourselves.
+		 */
+		if (columnNames == null)
+		{
+			int [] baseCols = irg.baseColumnPositions();
+			columnNames = new String[baseCols.length];
+			ColumnDescriptorList colDL = td.getColumnDescriptorList();
+			for (int i = 0; i < baseCols.length; i++)
+			{
+				columnNames[i] =
+					colDL.elementAt(baseCols[i]-1).getColumnName();
+			}
+		}
 	}
 
 	///////////////////////////////////////////////
@@ -298,33 +385,53 @@
 				maxBaseColumnPosition = baseColumnPositions[i];
 		}
 
+		/* The code below tries to determine if the index that we're about
+		 * to create can "share" a conglomerate with an existing index.
+		 * If so, we will use a single physical conglomerate--namely, the
+		 * one that already exists--to support both indexes. I.e. we will
+		 * *not* create a new conglomerate as part of this constant action.
+		 */ 
+
 		// check if we have similar indices already for this table
 		ConglomerateDescriptor[] congDescs = td.getConglomerateDescriptors();
-		boolean duplicate = false;
-        long conglomId = 0;
-
+		boolean shareExisting = false;
 		for (int i = 0; i < congDescs.length; i++)
 		{
 			ConglomerateDescriptor cd = congDescs[i];
 			if ( ! cd.isIndex())
 				continue;
+
+			if (droppedConglomNum == cd.getConglomerateNumber())
+			{
+				/* We can't share with any conglomerate descriptor
+				 * whose conglomerate number matches the dropped
+				 * conglomerate number, because that descriptor's
+				 * backing conglomerate was dropped, as well.  If
+				 * we're going to share, we have to share with a
+				 * descriptor whose backing physical conglomerate
+				 * is still around.
+				 */
+				continue;
+			}
+
 			IndexRowGenerator irg = cd.getIndexDescriptor();
 			int[] bcps = irg.baseColumnPositions();
 			boolean[] ia = irg.isAscending();
 			int j = 0;
 
-			/* For an index to be considered a duplicate of already existing index, the
-			 * following conditions have to be satisfied:
+			/* The conditions which allow an index to share an existing
+			 * conglomerate are as follows:
+			 *
 			 * 1. the set of columns (both key and include columns) and their 
 			 *  order in the index is the same as that of an existing index AND 
 			 * 2. the ordering attributes are the same AND 
 			 * 3. both the previously existing index and the one being created 
 			 *  are non-unique OR the previously existing index is unique
-			 */
+			 */ 
+			boolean possibleShare = (irg.isUnique() || !unique) &&
+			    (bcps.length == baseColumnPositions.length);
 
-			if ((bcps.length == baseColumnPositions.length) &&
-			    (irg.isUnique() || !unique) &&
-				indexType.equals(irg.indexType()))
+			if (possibleShare && indexType.equals(irg.indexType()))
 			{
 				for (; j < bcps.length; j++)
 				{
@@ -333,7 +440,7 @@
 				}
 			}
 
-			if (j == baseColumnPositions.length)	// duplicate
+			if (j == baseColumnPositions.length)	// share
 			{
 				/*
 				 * Don't allow users to create a duplicate index. Allow if being done internally
@@ -349,23 +456,53 @@
 					return;
 				}
 
-				//Duplicate indexes share the physical conglomerate underneath
+				/* Sharing indexes share the physical conglomerate
+				 * underneath, so pull the conglomerate number from
+				 * the existing conglomerate descriptor.
+				 */
 				conglomId = cd.getConglomerateNumber();
-				indexRowGenerator = cd.getIndexDescriptor();
+
+				/* We create a new IndexRowGenerator because certain
+				 * attributes--esp. uniqueness--may be different between
+				 * the index we're creating and the conglomerate that
+				 * already exists.  I.e. even though we're sharing a
+				 * conglomerate, the new index is not necessarily
+				 * identical to the existing conglomerate. We have to
+				 * keep track of that info so that if we later drop
+				 * the shared physical conglomerate, we can figure out
+				 * what this index (the one we're creating now) is
+				 * really supposed to look like.
+				 */
+				indexRowGenerator =
+					new IndexRowGenerator(
+						indexType, unique,
+						baseColumnPositions,
+						isAscending,
+						baseColumnPositions.length);
+
 				//DERBY-655 and DERBY-1343  
-				//Duplicate indexes will have unqiue logical conglomerate UUIDs.  
+				// Sharing indexes will have unique logical conglomerate UUIDs.
 				conglomerateUUID = dd.getUUIDFactory().createUUID();
-				duplicate = true;
+				shareExisting = true;
 				break;
 			}
 		}
 
+		/* If we have a droppedConglomNum then the index we're about to
+		 * "create" already exists--i.e. it has an index descriptor and
+		 * the corresponding information is already in the system catalogs.
+		 * The only thing we're missing, then, is the physical conglomerate
+		 * to back the index (because the old conglomerate was dropped).
+		 */
+		boolean alreadyHaveConglomDescriptor = (droppedConglomNum > -1L);
+
 		/* If this index already has an essentially same one, we share the
 		 * conglomerate with the old one, and just simply add a descriptor
-		 * entry into SYSCONGLOMERATES.
+		 * entry into SYSCONGLOMERATES--unless we already have a descriptor,
+		 * in which case we don't even need to do that.
 		 */
 		DataDescriptorGenerator ddg = dd.getDataDescriptorGenerator();
-		if (duplicate)
+		if (shareExisting && !alreadyHaveConglomDescriptor)
 		{
 			ConglomerateDescriptor cgd =
 				ddg.newConglomerateDescriptor(conglomId, indexName, true,
@@ -416,7 +553,7 @@
 							Integer.toString(baseColumnPositions.length + 1));
 
 		// For now, assume that all index columns are ordered columns
-		if (! duplicate)
+		if (! shareExisting)
 		{
 			indexRowGenerator = new IndexRowGenerator(indexType, unique,
 													baseColumnPositions,
@@ -527,9 +664,9 @@
 				indexRowGenerator.getIndexRow(compactBaseRows[i], rl[i], indexRows[i], bitSet);
 			}
 
-			/* now that we got indexTemplateRow, done for duplicate index
+			/* now that we got indexTemplateRow, done for sharing index
 			 */
-			if (duplicate)
+			if (shareExisting)
 				return;
 
 			/* For non-unique indexes, we order by all columns + the RID.
@@ -646,21 +783,32 @@
 		indexController.close();
 
 		//
-		// Create a conglomerate descriptor with the conglomId filled in and
-		// add it.
+		// Create a conglomerate descriptor with the conglomId filled
+		// in and add it--if we don't have one already.
 		//
+		if (!alreadyHaveConglomDescriptor)
+		{
+			ConglomerateDescriptor cgd =
+				ddg.newConglomerateDescriptor(
+					conglomId, indexName, true,
+					indexRowGenerator, isConstraint,
+					conglomerateUUID, td.getUUID(), sd.getUUID() );
 
-		ConglomerateDescriptor cgd =
-			ddg.newConglomerateDescriptor(conglomId, indexName, true,
-										  indexRowGenerator, isConstraint,
-										  conglomerateUUID, td.getUUID(), sd.getUUID() );
+			dd.addDescriptor(cgd, sd,
+				DataDictionary.SYSCONGLOMERATES_CATALOG_NUM, false, tc);
 
-		dd.addDescriptor(cgd, sd, DataDictionary.SYSCONGLOMERATES_CATALOG_NUM, false, tc);
+			// add newly added conglomerate to the list of conglomerate
+			// descriptors in the td.
+			ConglomerateDescriptorList cdl = td.getConglomerateDescriptorList();
+			cdl.add(cgd);
 
-		// add newly added conglomerate to the list of conglomerate descriptors
-		// in the td.
-		ConglomerateDescriptorList cdl = td.getConglomerateDescriptorList();
-		cdl.add(cgd);
+			/* Since we created a new conglomerate descriptor, load
+			 * its UUID into the corresponding field, to ensure that
+			 * it is properly set in the StatisticsDescriptor created
+			 * below.
+			 */
+			conglomerateUUID = cgd.getUUID();
+		}
 
 		CardinalityCounter cCount = (CardinalityCounter)rowSource;
 		long numRows;
@@ -670,9 +818,11 @@
 			for (int i = 0; i < c.length; i++)
 			{
 				StatisticsDescriptor statDesc = 
-					new StatisticsDescriptor(dd, dd.getUUIDFactory().createUUID(),
-												cgd.getUUID(), td.getUUID(), "I", new StatisticsImpl(numRows, c[i]),
-												i + 1);
+					new StatisticsDescriptor(dd,
+						dd.getUUIDFactory().createUUID(),
+						conglomerateUUID, td.getUUID(), "I",
+						new StatisticsImpl(numRows, c[i]), i + 1);
+
 				dd.addDescriptor(statDesc, null, 
 								 DataDictionary.SYSSTATISTICS_CATALOG_NUM,
 								 true, tc);
@@ -690,6 +840,51 @@
 	ExecRow getIndexTemplateRow()
 	{
 		return indexTemplateRow;
+	}
+
+	/**
+	 * Get the conglomerate number for the conglomerate that was
+	 * created by this constant action.  Will return -1L if the
+	 * constant action has not yet been executed.  This is used
+	 * for updating conglomerate descriptors which share a
+	 * conglomerate that has been dropped, in which case those
+	 * "sharing" descriptors need to point to the newly-created
+	 * conglomerate (the newly-created conglomerate replaces
+	 * the dropped one).
+	 */
+	long getCreatedConglomNumber()
+	{
+		if (SanityManager.DEBUG)
+		{
+			if (conglomId == -1L)
+			{
+				SanityManager.THROWASSERT(
+					"Called getCreatedConglomNumber() on a CreateIndex" +
+					"ConstantAction before the action was executed.");
+			}
+		}
+
+		return conglomId;
+	}
+
+	/**
+	 * If the purpose of this constant action was to "replace" a
+	 * dropped physical conglomerate, then this method returns the
+	 * conglomerate number of the dropped conglomerate.  Otherwise
+	 * this method will end up returning -1.
+	 */
+	long getReplacedConglomNumber()
+	{
+		return droppedConglomNum;
+	}
+
+	/**
+	 * Get the UUID for the conglomerate descriptor that was created
+	 * (or re-used) by this constant action.
+	 */
+	UUID getCreatedUUID()
+	{
+		return conglomerateUUID;
 	}
 
 	/**



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