using System;
using System.Diagnostics;

using u8 = System.Byte;

namespace Community.CsharpSqlite
{
	using sqlite3_int64 = System.Int64;

	public partial class Sqlite3
	{
		/*
		** 2005 July 8
		**
		** The author disclaims copyright to this source code.  In place of
		** a legal notice, here is a blessing:
		**
		**    May you do good and not evil.
		**    May you find forgiveness for yourself and forgive others.
		**    May you share freely, never taking more than you give.
		**
		*************************************************************************
		** This file contains code associated with the ANALYZE command.
		*************************************************************************
		**  Included in SQLite3 port to C#-SQLite;  2008 Noah B Hart
		**  C#-SQLite is an independent reimplementation of the SQLite software library
		**
		**  SQLITE_SOURCE_ID: 2011-05-19 13:26:54 ed1da510a239ea767a01dc332b667119fa3c908e
		**
		*************************************************************************
		*/
#if !SQLITE_OMIT_ANALYZE
		//#include "sqliteInt.h"

		/*
		** This routine generates code that opens the sqlite_stat1 table for
		** writing with cursor iStatCur. If the library was built with the
		** SQLITE_ENABLE_STAT2 macro defined, then the sqlite_stat2 table is
		** opened for writing using cursor (iStatCur+1)
		**
		** If the sqlite_stat1 tables does not previously exist, it is created.
		** Similarly, if the sqlite_stat2 table does not exist and the library
		** is compiled with SQLITE_ENABLE_STAT2 defined, it is created.
		**
		** Argument zWhere may be a pointer to a buffer containing a table name,
		** or it may be a NULL pointer. If it is not NULL, then all entries in
		** the sqlite_stat1 and (if applicable) sqlite_stat2 tables associated
		** with the named table are deleted. If zWhere==0, then code is generated
		** to delete all stat table entries.
		*/

		public struct _aTable
		{
			public string zName;
			public string zCols;

			public _aTable(string zName, string zCols)
			{
				this.zName = zName;
				this.zCols = zCols;
			}
		};

		private static _aTable[] aTable = new _aTable[]{
new _aTable( "sqlite_stat1", "tbl,idx,stat" ),
#if SQLITE_ENABLE_STAT2
new _aTable( "sqlite_stat2", "tbl,idx,sampleno,sample" ),
#endif
};

		private static void openStatTable(
		Parse pParse,       /* Parsing context */
		int iDb,            /* The database we are looking in */
		int iStatCur,       /* Open the sqlite_stat1 table on this cursor */
		string zWhere,      /* Delete entries for this table or index */
		string zWhereType   /* Either "tbl" or "idx" */
		)
		{
			int[] aRoot = new int[] { 0, 0 };
			u8[] aCreateTbl = new u8[] { 0, 0 };

			int i;
			sqlite3 db = pParse.db;
			Db pDb;
			Vdbe v = sqlite3GetVdbe(pParse);

			if (v == null)
				return;
			Debug.Assert(sqlite3BtreeHoldsAllMutexes(db));
			Debug.Assert(sqlite3VdbeDb(v) == db);
			pDb = db.aDb[iDb];

			for (i = 0; i < ArraySize(aTable); i++)
			{
				string zTab = aTable[i].zName;
				Table pStat;
				if ((pStat = sqlite3FindTable(db, zTab, pDb.zName)) == null)
				{
					/* The sqlite_stat[12] table does not exist. Create it. Note that a
					** side-effect of the CREATE TABLE statement is to leave the rootpage
					** of the new table in register pParse.regRoot. This is important
					** because the OpenWrite opcode below will be needing it. */
					sqlite3NestedParse(pParse,
					"CREATE TABLE %Q.%s(%s)", pDb.zName, zTab, aTable[i].zCols
					);
					aRoot[i] = pParse.regRoot;
					aCreateTbl[i] = 1;
				}
				else
				{
					/* The table already exists. If zWhere is not NULL, delete all entries
					** associated with the table zWhere. If zWhere is NULL, delete the
					** entire contents of the table. */
					aRoot[i] = pStat.tnum;
					sqlite3TableLock(pParse, iDb, aRoot[i], 1, zTab);
					if (!String.IsNullOrEmpty(zWhere))
					{
						sqlite3NestedParse(pParse,
						"DELETE FROM %Q.%s WHERE %s=%Q", pDb.zName, zTab, zWhereType, zWhere
						);
					}
					else
					{
						/* The sqlite_stat[12] table already exists.  Delete all rows. */
						sqlite3VdbeAddOp2(v, OP_Clear, aRoot[i], iDb);
					}
				}
			}

			/* Open the sqlite_stat[12] tables for writing. */
			for (i = 0; i < ArraySize(aTable); i++)
			{
				sqlite3VdbeAddOp3(v, OP_OpenWrite, iStatCur + i, aRoot[i], iDb);
				sqlite3VdbeChangeP4(v, -1, 3, P4_INT32);
				sqlite3VdbeChangeP5(v, aCreateTbl[i]);
			}
		}

		/*
		** Generate code to do an analysis of all indices associated with
		** a single table.
		*/

		private static void analyzeOneTable(
		Parse pParse,    /* Parser context */
		Table pTab,      /* Table whose indices are to be analyzed */
		Index pOnlyIdx,   /* If not NULL, only analyze this one index */
		int iStatCur,    /* Index of VdbeCursor that writes the sqlite_stat1 table */
		int iMem         /* Available memory locations begin here */
		)
		{
			sqlite3 db = pParse.db;      /* Database handle */
			Index pIdx;                  /* An index to being analyzed */
			int iIdxCur;                 /* Cursor open on index being analyzed */
			Vdbe v;                      /* The virtual machine being built up */
			int i;                       /* Loop counter */
			int topOfLoop;               /* The top of the loop */
			int endOfLoop;               /* The end of the loop */
			int jZeroRows = -1;          /* Jump from here if number of rows is zero */
			int iDb;                     /* Index of database containing pTab */
			int regTabname = iMem++;     /* Register containing table name */
			int regIdxname = iMem++;     /* Register containing index name */
			int regSampleno = iMem++;    /* Register containing next sample number */
			int regCol = iMem++;         /* Content of a column analyzed table */
			int regRec = iMem++;         /* Register holding completed record */
			int regTemp = iMem++;        /* Temporary use register */
			int regRowid = iMem++;       /* Rowid for the inserted record */

#if SQLITE_ENABLE_STAT2
  int addr = 0;                /* Instruction address */
  int regTemp2 = iMem++;       /* Temporary use register */
  int regSamplerecno = iMem++; /* Index of next sample to record */
  int regRecno = iMem++;       /* Current sample index */
  int regLast = iMem++;        /* Index of last sample to record */
  int regFirst = iMem++;       /* Index of first sample to record */
#endif

			v = sqlite3GetVdbe(pParse);
			if (v == null || NEVER(pTab == null))
			{
				return;
			}
			if (pTab.tnum == 0)
			{
				/* Do not gather statistics on views or virtual tables */
				return;
			}
			if (pTab.zName.StartsWith("sqlite_", StringComparison.OrdinalIgnoreCase))
			{
				/* Do not gather statistics on system tables */
				return;
			}
			Debug.Assert(sqlite3BtreeHoldsAllMutexes(db));
			iDb = sqlite3SchemaToIndex(db, pTab.pSchema);
			Debug.Assert(iDb >= 0);
			Debug.Assert(sqlite3SchemaMutexHeld(db, iDb, null));
#if !SQLITE_OMIT_AUTHORIZATION
if( sqlite3AuthCheck(pParse, SQLITE_ANALYZE, pTab.zName, 0,
db.aDb[iDb].zName ) ){
return;
}
#endif

			/* Establish a read-lock on the table at the shared-cache level. */
			sqlite3TableLock(pParse, iDb, pTab.tnum, 0, pTab.zName);

			iIdxCur = pParse.nTab++;
			sqlite3VdbeAddOp4(v, OP_String8, 0, regTabname, 0, pTab.zName, 0);
			for (pIdx = pTab.pIndex; pIdx != null; pIdx = pIdx.pNext)
			{
				int nCol;
				KeyInfo pKey;
				if (pOnlyIdx != null && pOnlyIdx != pIdx)
					continue;
				nCol = pIdx.nColumn;
				pKey = sqlite3IndexKeyinfo(pParse, pIdx);

				if (iMem + 1 + (nCol * 2) > pParse.nMem)
				{
					pParse.nMem = iMem + 1 + (nCol * 2);
				}

				/* Open a cursor to the index to be analyzed. */
				Debug.Assert(iDb == sqlite3SchemaToIndex(db, pIdx.pSchema));
				sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIdx.tnum, iDb,
				pKey, P4_KEYINFO_HANDOFF);
				VdbeComment(v, "%s", pIdx.zName);

				/* Populate the registers containing the index names. */
				sqlite3VdbeAddOp4(v, OP_String8, 0, regIdxname, 0, pIdx.zName, 0);

#if SQLITE_ENABLE_STAT2

    /* If this iteration of the loop is generating code to analyze the
** first index in the pTab.pIndex list, then register regLast has
** not been populated. In this case populate it now.  */
    if ( pTab.pIndex == pIdx )
    {
      sqlite3VdbeAddOp2( v, OP_Integer, SQLITE_INDEX_SAMPLES, regSamplerecno );
      sqlite3VdbeAddOp2( v, OP_Integer, SQLITE_INDEX_SAMPLES * 2 - 1, regTemp );
      sqlite3VdbeAddOp2( v, OP_Integer, SQLITE_INDEX_SAMPLES * 2, regTemp2 );

      sqlite3VdbeAddOp2( v, OP_Count, iIdxCur, regLast );
      sqlite3VdbeAddOp2( v, OP_Null, 0, regFirst );
      addr = sqlite3VdbeAddOp3( v, OP_Lt, regSamplerecno, 0, regLast );
      sqlite3VdbeAddOp3( v, OP_Divide, regTemp2, regLast, regFirst );
      sqlite3VdbeAddOp3( v, OP_Multiply, regLast, regTemp, regLast );
      sqlite3VdbeAddOp2( v, OP_AddImm, regLast, SQLITE_INDEX_SAMPLES * 2 - 2 );
      sqlite3VdbeAddOp3( v, OP_Divide, regTemp2, regLast, regLast );
      sqlite3VdbeJumpHere( v, addr );
    }

    /* Zero the regSampleno and regRecno registers. */
    sqlite3VdbeAddOp2( v, OP_Integer, 0, regSampleno );
    sqlite3VdbeAddOp2( v, OP_Integer, 0, regRecno );
    sqlite3VdbeAddOp2( v, OP_Copy, regFirst, regSamplerecno );
#endif

				/* The block of memory cells initialized here is used as follows.
**
**    iMem:
**        The total number of rows in the table.
**
**    iMem+1 .. iMem+nCol:
**        Number of distinct entries in index considering the
**        left-most N columns only, where N is between 1 and nCol,
**        inclusive.
**
**    iMem+nCol+1 .. Mem+2*nCol:
**        Previous value of indexed columns, from left to right.
**
** Cells iMem through iMem+nCol are initialized to 0. The others are
** initialized to contain an SQL NULL.
*/
				for (i = 0; i <= nCol; i++)
				{
					sqlite3VdbeAddOp2(v, OP_Integer, 0, iMem + i);
				}
				for (i = 0; i < nCol; i++)
				{
					sqlite3VdbeAddOp2(v, OP_Null, 0, iMem + nCol + i + 1);
				}

				/* Start the analysis loop. This loop runs through all the entries in
				** the index b-tree.  */
				endOfLoop = sqlite3VdbeMakeLabel(v);
				sqlite3VdbeAddOp2(v, OP_Rewind, iIdxCur, endOfLoop);
				topOfLoop = sqlite3VdbeCurrentAddr(v);
				sqlite3VdbeAddOp2(v, OP_AddImm, iMem, 1);

				for (i = 0; i < nCol; i++)
				{
					sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regCol);
					CollSeq pColl;
					if (i == 0)
					{
#if SQLITE_ENABLE_STAT2
        /* Check if the record that cursor iIdxCur points to contains a
** value that should be stored in the sqlite_stat2 table. If so,
** store it.  */
        int ne = sqlite3VdbeAddOp3( v, OP_Ne, regRecno, 0, regSamplerecno );
        Debug.Assert( regTabname + 1 == regIdxname
        && regTabname + 2 == regSampleno
        && regTabname + 3 == regCol
        );
        sqlite3VdbeChangeP5( v, SQLITE_JUMPIFNULL );
        sqlite3VdbeAddOp4( v, OP_MakeRecord, regTabname, 4, regRec, "aaab", 0 );
        sqlite3VdbeAddOp2( v, OP_NewRowid, iStatCur + 1, regRowid );
        sqlite3VdbeAddOp3( v, OP_Insert, iStatCur + 1, regRec, regRowid );

        /* Calculate new values for regSamplerecno and regSampleno.
        **
        **   sampleno = sampleno + 1
        **   samplerecno = samplerecno+(remaining records)/(remaining samples)
        */
        sqlite3VdbeAddOp2( v, OP_AddImm, regSampleno, 1 );
        sqlite3VdbeAddOp3( v, OP_Subtract, regRecno, regLast, regTemp );
        sqlite3VdbeAddOp2( v, OP_AddImm, regTemp, -1 );
        sqlite3VdbeAddOp2( v, OP_Integer, SQLITE_INDEX_SAMPLES, regTemp2 );
        sqlite3VdbeAddOp3( v, OP_Subtract, regSampleno, regTemp2, regTemp2 );
        sqlite3VdbeAddOp3( v, OP_Divide, regTemp2, regTemp, regTemp );
        sqlite3VdbeAddOp3( v, OP_Add, regSamplerecno, regTemp, regSamplerecno );

        sqlite3VdbeJumpHere( v, ne );
        sqlite3VdbeAddOp2( v, OP_AddImm, regRecno, 1 );
#endif

						/* Always record the very first row */
						sqlite3VdbeAddOp1(v, OP_IfNot, iMem + 1);
					}
					Debug.Assert(pIdx.azColl != null);
					Debug.Assert(pIdx.azColl[i] != null);
					pColl = sqlite3LocateCollSeq(pParse, pIdx.azColl[i]);
					sqlite3VdbeAddOp4(v, OP_Ne, regCol, 0, iMem + nCol + i + 1,
					pColl, P4_COLLSEQ);
					sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
				}
				//if( db.mallocFailed ){
				//  /* If a malloc failure has occurred, then the result of the expression
				//  ** passed as the second argument to the call to sqlite3VdbeJumpHere()
				//  ** below may be negative. Which causes an Debug.Assert() to fail (or an
				//  ** out-of-bounds write if SQLITE_DEBUG is not defined).  */
				//  return;
				//}
				sqlite3VdbeAddOp2(v, OP_Goto, 0, endOfLoop);
				for (i = 0; i < nCol; i++)
				{
					int addr2 = sqlite3VdbeCurrentAddr(v) - (nCol * 2);
					if (i == 0)
					{
						sqlite3VdbeJumpHere(v, addr2 - 1);  /* Set jump dest for the OP_IfNot */
					}
					sqlite3VdbeJumpHere(v, addr2);      /* Set jump dest for the OP_Ne */
					sqlite3VdbeAddOp2(v, OP_AddImm, iMem + i + 1, 1);
					sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, iMem + nCol + i + 1);
				}

				/* End of the analysis loop. */
				sqlite3VdbeResolveLabel(v, endOfLoop);
				sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, topOfLoop);
				sqlite3VdbeAddOp1(v, OP_Close, iIdxCur);

				/* Store the results in sqlite_stat1.
				**
				** The result is a single row of the sqlite_stat1 table.  The first
				** two columns are the names of the table and index.  The third column
				** is a string composed of a list of integer statistics about the
				** index.  The first integer in the list is the total number of entries
				** in the index.  There is one additional integer in the list for each
				** column of the table.  This additional integer is a guess of how many
				** rows of the table the index will select.  If D is the count of distinct
				** values and K is the total number of rows, then the integer is computed
				** as:
				**
				**        I = (K+D-1)/D
				**
				** If K==0 then no entry is made into the sqlite_stat1 table.
				** If K>0 then it is always the case the D>0 so division by zero
				** is never possible.
				*/
				sqlite3VdbeAddOp2(v, OP_SCopy, iMem, regSampleno);
				if (jZeroRows < 0)
				{
					jZeroRows = sqlite3VdbeAddOp1(v, OP_IfNot, iMem);
				}
				for (i = 0; i < nCol; i++)
				{
					sqlite3VdbeAddOp4(v, OP_String8, 0, regTemp, 0, " ", 0);
					sqlite3VdbeAddOp3(v, OP_Concat, regTemp, regSampleno, regSampleno);
					sqlite3VdbeAddOp3(v, OP_Add, iMem, iMem + i + 1, regTemp);
					sqlite3VdbeAddOp2(v, OP_AddImm, regTemp, -1);
					sqlite3VdbeAddOp3(v, OP_Divide, iMem + i + 1, regTemp, regTemp);
					sqlite3VdbeAddOp1(v, OP_ToInt, regTemp);
					sqlite3VdbeAddOp3(v, OP_Concat, regTemp, regSampleno, regSampleno);
				}
				sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regRec, "aaa", 0);
				sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regRowid);
				sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regRec, regRowid);
				sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
			}

			/* If the table has no indices, create a single sqlite_stat1 entry
			** containing NULL as the index name and the row count as the content.
			*/
			if (pTab.pIndex == null)
			{
				sqlite3VdbeAddOp3(v, OP_OpenRead, iIdxCur, pTab.tnum, iDb);
				VdbeComment(v, "%s", pTab.zName);
				sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regSampleno);
				sqlite3VdbeAddOp1(v, OP_Close, iIdxCur);
				jZeroRows = sqlite3VdbeAddOp1(v, OP_IfNot, regSampleno);
			}
			else
			{
				sqlite3VdbeJumpHere(v, jZeroRows);
				jZeroRows = sqlite3VdbeAddOp0(v, OP_Goto);
			}
			sqlite3VdbeAddOp2(v, OP_Null, 0, regIdxname);
			sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regRec, "aaa", 0);
			sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regRowid);
			sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regRec, regRowid);
			sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
			if (pParse.nMem < regRec)
				pParse.nMem = regRec;
			sqlite3VdbeJumpHere(v, jZeroRows);
		}

		/*
		** Generate code that will cause the most recent index analysis to
		** be loaded into internal hash tables where is can be used.
		*/

		private static void loadAnalysis(Parse pParse, int iDb)
		{
			Vdbe v = sqlite3GetVdbe(pParse);
			if (v != null)
			{
				sqlite3VdbeAddOp1(v, OP_LoadAnalysis, iDb);
			}
		}

		/*
		** Generate code that will do an analysis of an entire database
		*/

		private static void analyzeDatabase(Parse pParse, int iDb)
		{
			sqlite3 db = pParse.db;
			Schema pSchema = db.aDb[iDb].pSchema;    /* Schema of database iDb */
			HashElem k;
			int iStatCur;
			int iMem;

			sqlite3BeginWriteOperation(pParse, 0, iDb);
			iStatCur = pParse.nTab;
			pParse.nTab += 2;
			openStatTable(pParse, iDb, iStatCur, null, null);
			iMem = pParse.nMem + 1;
			Debug.Assert(sqlite3SchemaMutexHeld(db, iDb, null));
			//for(k=sqliteHashFirst(pSchema.tblHash); k; k=sqliteHashNext(k)){
			for (k = pSchema.tblHash.first; k != null; k = k.next)
			{
				Table pTab = (Table)k.data;// sqliteHashData( k );
				analyzeOneTable(pParse, pTab, null, iStatCur, iMem);
			}
			loadAnalysis(pParse, iDb);
		}

		/*
		** Generate code that will do an analysis of a single table in
		** a database.  If pOnlyIdx is not NULL then it is a single index
		** in pTab that should be analyzed.
		*/

		private static void analyzeTable(Parse pParse, Table pTab, Index pOnlyIdx)
		{
			int iDb;
			int iStatCur;

			Debug.Assert(pTab != null);
			Debug.Assert(sqlite3BtreeHoldsAllMutexes(pParse.db));
			iDb = sqlite3SchemaToIndex(pParse.db, pTab.pSchema);
			sqlite3BeginWriteOperation(pParse, 0, iDb);
			iStatCur = pParse.nTab;
			pParse.nTab += 2;
			if (pOnlyIdx != null)
			{
				openStatTable(pParse, iDb, iStatCur, pOnlyIdx.zName, "idx");
			}
			else
			{
				openStatTable(pParse, iDb, iStatCur, pTab.zName, "tbl");
			}
			analyzeOneTable(pParse, pTab, pOnlyIdx, iStatCur, pParse.nMem + 1);
			loadAnalysis(pParse, iDb);
		}

		/*
		** Generate code for the ANALYZE command.  The parser calls this routine
		** when it recognizes an ANALYZE command.
		**
		**        ANALYZE                            -- 1
		**        ANALYZE  <database>                -- 2
		**        ANALYZE  ?<database>.?<tablename>  -- 3
		**
		** Form 1 causes all indices in all attached databases to be analyzed.
		** Form 2 analyzes all indices the single database named.
		** Form 3 analyzes all indices associated with the named table.
		*/

		// OVERLOADS, so I don't need to rewrite parse.c
		private static void sqlite3Analyze(Parse pParse, int null_2, int null_3)
		{
			sqlite3Analyze(pParse, null, null);
		}

		private static void sqlite3Analyze(Parse pParse, Token pName1, Token pName2)
		{
			sqlite3 db = pParse.db;
			int iDb;
			int i;
			string z, zDb;
			Table pTab;
			Index pIdx;
			Token pTableName = null;

			/* Read the database schema. If an error occurs, leave an error message
			** and code in pParse and return NULL. */
			Debug.Assert(sqlite3BtreeHoldsAllMutexes(pParse.db));
			if (SQLITE_OK != sqlite3ReadSchema(pParse))
			{
				return;
			}

			Debug.Assert(pName2 != null || pName1 == null);
			if (pName1 == null)
			{
				/* Form 1:  Analyze everything */
				for (i = 0; i < db.nDb; i++)
				{
					if (i == 1)
						continue;  /* Do not analyze the TEMP database */
					analyzeDatabase(pParse, i);
				}
			}
			else if (pName2.n == 0)
			{
				/* Form 2:  Analyze the database or table named */
				iDb = sqlite3FindDb(db, pName1);
				if (iDb >= 0)
				{
					analyzeDatabase(pParse, iDb);
				}
				else
				{
					z = sqlite3NameFromToken(db, pName1);
					if (z != null)
					{
						if ((pIdx = sqlite3FindIndex(db, z, null)) != null)
						{
							analyzeTable(pParse, pIdx.pTable, pIdx);
						}
						else if ((pTab = sqlite3LocateTable(pParse, 0, z, null)) != null)
						{
							analyzeTable(pParse, pTab, null);
						}
						z = null;//sqlite3DbFree( db, z );
					}
				}
			}
			else
			{
				/* Form 3: Analyze the fully qualified table name */
				iDb = sqlite3TwoPartName(pParse, pName1, pName2, ref pTableName);
				if (iDb >= 0)
				{
					zDb = db.aDb[iDb].zName;
					z = sqlite3NameFromToken(db, pTableName);
					if (z != null)
					{
						if ((pIdx = sqlite3FindIndex(db, z, zDb)) != null)
						{
							analyzeTable(pParse, pIdx.pTable, pIdx);
						}
						else if ((pTab = sqlite3LocateTable(pParse, 0, z, zDb)) != null)
						{
							analyzeTable(pParse, pTab, null);
						}
						z = null; //sqlite3DbFree( db, z );
					}
				}
			}
		}

		/*
		** Used to pass information from the analyzer reader through to the
		** callback routine.
		*/

		//typedef struct analysisInfo analysisInfo;
		public struct analysisInfo
		{
			public sqlite3 db;
			public string zDatabase;
		};

		/*
		** This callback is invoked once for each index when reading the
		** sqlite_stat1 table.
		**
		**     argv[0] = name of the table
		**     argv[1] = name of the index (might be NULL)
		**     argv[2] = results of analysis - on integer for each column
		**
		** Entries for which argv[1]==NULL simply record the number of rows in
		** the table.
		*/

		private static int analysisLoader(object pData, sqlite3_int64 argc, object Oargv, object NotUsed)
		{
			string[] argv = (string[])Oargv;
			analysisInfo pInfo = (analysisInfo)pData;
			Index pIndex;
			Table pTable;
			int i, c, n;
			int v;
			string z;

			Debug.Assert(argc == 3);
			UNUSED_PARAMETER2(NotUsed, argc);
			if (argv == null || argv[0] == null || argv[2] == null)
			{
				return 0;
			}
			pTable = sqlite3FindTable(pInfo.db, argv[0], pInfo.zDatabase);
			if (pTable == null)
			{
				return 0;
			}
			if (!String.IsNullOrEmpty(argv[1]))
			{
				pIndex = sqlite3FindIndex(pInfo.db, argv[1], pInfo.zDatabase);
			}
			else
			{
				pIndex = null;
			}

			n = pIndex != null ? pIndex.nColumn : 0;
			z = argv[2];
			int zIndex = 0;
			for (i = 0; z != null && i <= n; i++)
			{
				v = 0;
				while (zIndex < z.Length && (c = z[zIndex]) >= '0' && c <= '9')
				{
					v = v * 10 + c - '0';
					zIndex++;
				}
				if (i == 0)
					pTable.nRowEst = (uint)v;
				if (pIndex == null)
					break;
				pIndex.aiRowEst[i] = v;
				if (zIndex < z.Length && z[zIndex] == ' ')
					zIndex++;
				if (z.Substring(zIndex).CompareTo("unordered") == 0)//memcmp( z, "unordered", 10 ) == 0 )
				{
					pIndex.bUnordered = 1;
					break;
				}
			}
			return 0;
		}

		/*
		** If the Index.aSample variable is not NULL, delete the aSample[] array
		** and its contents.
		*/

		private static void sqlite3DeleteIndexSamples(sqlite3 db, Index pIdx)
		{
#if SQLITE_ENABLE_STAT2
  if ( pIdx.aSample != null )
  {
    int j;
    for ( j = 0; j < SQLITE_INDEX_SAMPLES; j++ )
    {
      IndexSample p = pIdx.aSample[j];
      if ( p.eType == SQLITE_TEXT || p.eType == SQLITE_BLOB )
      {
        p.u.z = null;//sqlite3DbFree(db, p.u.z);
        p.u.zBLOB = null;
      }
    }
    sqlite3DbFree( db, ref pIdx.aSample );
  }
#else
			UNUSED_PARAMETER(db);
			UNUSED_PARAMETER(pIdx);
#endif
		}

		/*
		** Load the content of the sqlite_stat1 and sqlite_stat2 tables. The
		** contents of sqlite_stat1 are used to populate the Index.aiRowEst[]
		** arrays. The contents of sqlite_stat2 are used to populate the
		** Index.aSample[] arrays.
		**
		** If the sqlite_stat1 table is not present in the database, SQLITE_ERROR
		** is returned. In this case, even if SQLITE_ENABLE_STAT2 was defined
		** during compilation and the sqlite_stat2 table is present, no data is
		** read from it.
		**
		** If SQLITE_ENABLE_STAT2 was defined during compilation and the
		** sqlite_stat2 table is not present in the database, SQLITE_ERROR is
		** returned. However, in this case, data is read from the sqlite_stat1
		** table (if it is present) before returning.
		**
		** If an OOM error occurs, this function always sets db.mallocFailed.
		** This means if the caller does not care about other errors, the return
		** code may be ignored.
		*/

		private static int sqlite3AnalysisLoad(sqlite3 db, int iDb)
		{
			analysisInfo sInfo;
			HashElem i;
			string zSql;
			int rc;

			Debug.Assert(iDb >= 0 && iDb < db.nDb);
			Debug.Assert(db.aDb[iDb].pBt != null);
			/* Clear any prior statistics */
			Debug.Assert(sqlite3SchemaMutexHeld(db, iDb, null));
			//for(i=sqliteHashFirst(&db.aDb[iDb].pSchema.idxHash);i;i=sqliteHashNext(i)){
			for (i = db.aDb[iDb].pSchema.idxHash.first; i != null; i = i.next)
			{
				Index pIdx = (Index)i.data;// sqliteHashData( i );
				sqlite3DefaultRowEst(pIdx);
				sqlite3DeleteIndexSamples(db, pIdx);
				pIdx.aSample = null;
			}

			/* Check to make sure the sqlite_stat1 table exists */
			sInfo.db = db;
			sInfo.zDatabase = db.aDb[iDb].zName;
			if (sqlite3FindTable(db, "sqlite_stat1", sInfo.zDatabase) == null)
			{
				return SQLITE_ERROR;
			}

			/* Load new statistics out of the sqlite_stat1 table */
			zSql = sqlite3MPrintf(db,
			"SELECT tbl, idx, stat FROM %Q.sqlite_stat1", sInfo.zDatabase);
			//if ( zSql == null )
			//{
			//  rc = SQLITE_NOMEM;
			//}
			//else
			{
				rc = sqlite3_exec(db, zSql, (dxCallback)analysisLoader, sInfo, 0);
				sqlite3DbFree(db, ref zSql);
			}

			/* Load the statistics from the sqlite_stat2 table. */
#if SQLITE_ENABLE_STAT2
  if ( rc == SQLITE_OK && null == sqlite3FindTable( db, "sqlite_stat2", sInfo.zDatabase ) )
  {
    rc = SQLITE_ERROR;
  }
  if ( rc == SQLITE_OK )
  {
    sqlite3_stmt pStmt = null;

    zSql = sqlite3MPrintf( db,
    "SELECT idx,sampleno,sample FROM %Q.sqlite_stat2", sInfo.zDatabase );
    //if( null==zSql ){
    //rc = SQLITE_NOMEM;
    //}else{
    rc = sqlite3_prepare( db, zSql, -1, ref pStmt, 0 );
    sqlite3DbFree( db, ref zSql );
    //}

    if ( rc == SQLITE_OK )
    {
      while ( sqlite3_step( pStmt ) == SQLITE_ROW )
      {
        string zIndex;   /* Index name */
        Index pIdx;    /* Pointer to the index object */
        zIndex = sqlite3_column_text( pStmt, 0 );
        pIdx = !String.IsNullOrEmpty( zIndex ) ? sqlite3FindIndex( db, zIndex, sInfo.zDatabase ) : null;
        if ( pIdx != null )
        {
          int iSample = sqlite3_column_int( pStmt, 1 );
          if ( iSample < SQLITE_INDEX_SAMPLES && iSample >= 0 )
          {
            int eType = sqlite3_column_type( pStmt, 2 );

            if ( pIdx.aSample == null )
            {
              //static const int sz = sizeof(IndexSample)*SQLITE_INDEX_SAMPLES;
              //pIdx->aSample = (IndexSample )sqlite3DbMallocRaw(0, sz);
              //if( pIdx.aSample==0 ){
              //db.mallocFailed = 1;
              //break;
              //}
              pIdx.aSample = new IndexSample[SQLITE_INDEX_SAMPLES];//memset(pIdx->aSample, 0, sz);
            }

            //Debug.Assert( pIdx.aSample != null );
            if ( pIdx.aSample[iSample] == null )
              pIdx.aSample[iSample] = new IndexSample();
            IndexSample pSample = pIdx.aSample[iSample];
            {
              pSample.eType = (u8)eType;
              if ( eType == SQLITE_INTEGER || eType == SQLITE_FLOAT )
              {
                pSample.u.r = sqlite3_column_double( pStmt, 2 );
              }
              else if ( eType == SQLITE_TEXT || eType == SQLITE_BLOB )
              {
                string z = null;
                byte[] zBLOB = null;
                //string z = (string )(
                //(eType==SQLITE_BLOB) ?
                //sqlite3_column_blob(pStmt, 2):
                //sqlite3_column_text(pStmt, 2)
                //);
                if ( eType == SQLITE_BLOB )
                  zBLOB = sqlite3_column_blob( pStmt, 2 );
                else
                  z = sqlite3_column_text( pStmt, 2 );
                int n = sqlite3_column_bytes( pStmt, 2 );
                if ( n > 24 )
                {
                  n = 24;
                }
                pSample.nByte = (u8)n;
                if ( n < 1 )
                {
                  pSample.u.z = null;
                  pSample.u.zBLOB = null;
                }
                else
                {
                  pSample.u.z = z;
                  pSample.u.zBLOB = zBLOB;
                  //pSample->u.z = sqlite3DbMallocRaw(dbMem, n);
                  //if( pSample->u.z ){
                  //  memcpy(pSample->u.z, z, n);
                  //}else{
                  //  db->mallocFailed = 1;
                  //  break;
                  //}
                }
              }
            }
          }
        }
      }
      rc = sqlite3_finalize( pStmt );
    }
  }
#endif

			//if( rc==SQLITE_NOMEM ){
			//  db.mallocFailed = 1;
			//}
			return rc;
		}

#endif // * SQLITE_OMIT_ANALYZE */
	}
}