Hibernate中应对ORA-01795错误的最高效方法是什么？

Question

我需要通过Hibernate查询超过1000个元素，然后当我使用Oracle品牌时，我收到了错误信息“ORA-01795:列表中表达式的最大数量为1000”。

SELECT * FROM matable WHERE column IN (?,?,...) (>1000 items) 

我找到了许多解决方案： 使用OR拆分列表

where A in (a,b,c,d,e,f)

becomes

where (A in (a,b,c) OR a in (d,e,f)) ...

使用UNION ALL创建表格

SELECT * FROM maintable
JOIN (
    SELECT v1 a FROM DUAL UNION ALL
    SELECT v2 a FROM DUAL UNION ALL
    SELECT v3 a FROM DUAL UNION ALL
    ...
    SELECT v2000 a FROM DUAL) tmp

    on tmp.a = maintable.id

使用元组来避免限制

where (column,0) in ((1,0),(2,0),(3,0),(4,0), ... ,(1500,0))

使用临时表..

where A in SELECT item FROM my_temporary_table

参考这里，那里和那里的内容。

我的问题如下：如何处理此问题最佳实践？我所指的最佳实践是最有效的，但不仅限于Oracle；如果我使用Hibernate，则不想为每个数据库品牌创建和管理不同的代码（我只关心Oracle、MS SQL和PostGre）。

我的第一反应是使用临时表，但我不知道哪种方法对性能影响最大。

- gvo

---

我的直觉也是使用临时表。然而，你已经有了数据和代码；什么阻止你自己测试并找出哪个在特定情况下运行最快？ - Boneist

你说得对，我可以进行测试（也许会这样做），但我也想了解数据库如何处理/优化每种类型的查询，以及哪种查询更/不太昂贵。 - gvo

Answer 1

使用临时表并将值设置为主键。这可以非常有效地优化比较操作。最可能的是索引查找，尽管如果表非常小，Oracle可能会选择其他方法，例如表扫描。

在几乎任何数据库中，这种方法应该比使用1,000个“or”条件更快。有时类似地优化了“in”（使用二叉树存储值）。在这样的数据库中，性能将类似。

- Gordon Linoff

---

谢谢你的回答。这意味着“IN”语句中的值存储在类似于内存中的索引中，并通过OR语句逐个测试吗？如果我使用OR，我将不会使用1000个或条件，而是使用n个包含1000个元素的列表，由OR连接。 - gvo

我正在为这个答案投票，此外我建议将该表创建为索引有序表，以便行按主键顺序组织，并且主键和索引不会重复，因为它们在一个地方内部存储。 - Martina

谢谢您的评论，我不知道索引组织表的存在。 - gvo

Answer 2

我通过对hibernate-core jar的一些更改来解决了这个问题。

我制作了一个辅助类以将表达式拆分成更多的联接，例如：... t.column IN (: list_1) OR t.column IN (: list_2) ...，然后我将hibernate中的AbstractQueryImpl.expandParameterList方法更改为在集合超过限制时调用我的方法。
我的hibernate-core版本是3.6.10.Final，但它可以正常工作，并且针对4.x版本进行了测试。
我的代码已经测试过以下案例：

  where t.id in (:idList)
  where (t.id in (:idList))
  where ((t.id) in (:idList))
  where 1=1 and t.id in (:idList)
  where 1=1 and (t.id in (:idList))
  where 1=1 and(t.id) in (:idList)
  where 1=1 and((t.id) in (:idList))
  where 1=1 and(t.id in (:idList))

  where t.id not in (:idList)
  where (t.id not in (:idList))
  where ((t.id) not in (:idList))

AbstractQueryImpl.expandParameterList：

private String expandParameterList(String query, String name, TypedValue typedList, Map namedParamsCopy) {
    Collection vals = (Collection) typedList.getValue();
    Type type = typedList.getType();

    boolean isJpaPositionalParam = parameterMetadata.getNamedParameterDescriptor( name ).isJpaStyle();
    String paramPrefix = isJpaPositionalParam ? "?" : ParserHelper.HQL_VARIABLE_PREFIX;
    String placeholder =
            new StringBuffer( paramPrefix.length() + name.length() )
                    .append( paramPrefix ).append(  name )
                    .toString();

    if ( query == null ) {
        return query;
    }
    int loc = query.indexOf( placeholder );

    if ( loc < 0 ) {
        return query;
    }

    String beforePlaceholder = query.substring( 0, loc );
    String afterPlaceholder =  query.substring( loc + placeholder.length() );

    // check if placeholder is already immediately enclosed in parentheses
    // (ignoring whitespace)
    boolean isEnclosedInParens =
            StringHelper.getLastNonWhitespaceCharacter( beforePlaceholder ) == '(' &&
                    StringHelper.getFirstNonWhitespaceCharacter( afterPlaceholder ) == ')';

    if ( vals.size() == 1  && isEnclosedInParens ) {
        // short-circuit for performance when only 1 value and the
        // placeholder is already enclosed in parentheses...
        namedParamsCopy.put( name, new TypedValue( type, vals.iterator().next(), session.getEntityMode() ) );
        return query;
    }

    // *** changes by Vasile Bors for HHH-1123 ***
    // case vals.size() > 1000
    if ((vals.size() >= InExpressionExpander.MAX_ALLOWED_PER_INEXPR) && isEnclosedInParens) {

        InExpressionExpander inExpressionExpander = new InExpressionExpander(beforePlaceholder, afterPlaceholder);
        if(inExpressionExpander.isValidInOrNotInExpression()){

            List<String> list = new ArrayList<String>( vals.size() );
            Iterator iter = vals.iterator();
            int i = 0;
            String alias;
            while ( iter.hasNext() ) {
                alias = ( isJpaPositionalParam ? 'x' + name : name ) + i++ + '_';
                namedParamsCopy.put( alias, new TypedValue( type, iter.next(), session.getEntityMode() ) );
                list.add(ParserHelper.HQL_VARIABLE_PREFIX + alias );
            }

            String expandedExpression = inExpressionExpander.expandExpression(list);
            if(expandedExpression != null){
                return expandedExpression;
            }
        }
    }
    // *** end changes by Vasile Bors for HHH-1123 ***

    StringBuffer list = new StringBuffer(16);
    Iterator iter = vals.iterator();
    int i = 0;
    while (iter.hasNext()) {
        String alias = (isJpaPositionalParam ? 'x' + name : name) + i++ + '_';
        namedParamsCopy.put(alias, new TypedValue(type, iter.next(), session.getEntityMode()));
        list.append(ParserHelper.HQL_VARIABLE_PREFIX).append(alias);
        if (iter.hasNext()) {
            list.append(", ");
        }
    }

    return StringHelper.replace(
            beforePlaceholder,
            afterPlaceholder,
            placeholder.toString(),
            list.toString(),
            true,
            true
    );
}

我的辅助类InExpressionExpander：

包org.hibernate.util；

import org.hibernate.QueryException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Iterator;
import java.util.List;
import java.util.Stack;

/**
 * Utility class for expand Hql and Sql IN expressions with a parameter with more than IN expression limit size (HHH-1123).
 * <br/>
 * It work for expression with formats:
 * <pre>
 *
 * where t.id in (:idList)
 * where (t.id in (:idList))
 * where ((t.id) in (:idList))
 * where 1=1 and t.id in (:idList)
 * where 1=1 and (t.id in (:idList))
 * where 1=1 and(t.id) in (:idList)
 * where 1=1 and((t.id) in (:idList))
 * where 1=1 and(t.id in (:idList))
 *
 * where t.id not in (:idList)
 * where (t.id not in (:idList))
 * where ((t.id) not in (:idList))
 * </pre>
 * <p/>
 * Example:
 * <pre>
 * select t.id from tableOrEntity t where t.id IN (:idList)
 * </pre
 *
 * @author Vasile Bors
 * @since 13/12/2015.
 */
public class InExpressionExpander {
    private static final Logger log = LoggerFactory.getLogger(InExpressionExpander.class);

    public static final  int MAX_ALLOWED_PER_INEXPR = 1000;
    private static final int MAX_PARAMS_PER_INEXPR  = 500;

    private Stack<String> stackExpr = new Stack<String>();
    private StringBuilder toWalkQuery;

    private final String beforePlaceholder;
    private final String afterPlaceholder;
    private boolean wasChecked         = false;
    private boolean isEnclosedInParens = false;
    private boolean isInExpr           = false;
    private boolean isNotInExpr        = false;

    public InExpressionExpander(String beforePlaceholder, String afterPlaceholder) {
        this.toWalkQuery = new StringBuilder(beforePlaceholder);

        this.beforePlaceholder = beforePlaceholder;
        this.afterPlaceholder = afterPlaceholder;
    }

    public boolean isValidInOrNotInExpression() {
        if (!wasChecked) {
            String lastExpr = extractLastExpression();
            if ("(".equals(lastExpr)) {
                isEnclosedInParens = true;
                lastExpr = extractLastExpression();
            }
            isInExpr = "in".equalsIgnoreCase(lastExpr);
        }

        wasChecked = true;
        return isInExpr;
    }

    public String expandExpression(List paramList) {
        if (isValidInOrNotInExpression()) {

            final String lastExpr = extractLastExpression(false);

            if ("not".equalsIgnoreCase(lastExpr)) {
                isNotInExpr = true;
                extractLastExpression(); //extract "not" and consume it
            }

            extractColumnForInExpression();

            StringBuilder exprPrefixBuilder = new StringBuilder();
            for (int i = stackExpr.size() - 1; i > -1; i--) {
                exprPrefixBuilder.append(stackExpr.get(i)).append(' ');
            }
            if (!isEnclosedInParens) {
                exprPrefixBuilder.append('(');
            }

            String expandedExpression = expandInExpression(exprPrefixBuilder, paramList);
            String beforeExpression = getBeforeExpression();
            String afterExpression = getAfterExpression();

            String expandedQuery = new StringBuilder(beforeExpression).append(expandedExpression)
                    .append(afterExpression)
                    .toString();

            if (log.isDebugEnabled()) {
                log.debug(
                        "Query was changed to prevent exception for maximum number of expression in a list. Expanded IN expression query:\n {}",
                        expandedExpression);

                log.debug("Expanded query:\n {}", expandedQuery);
            }

            return expandedQuery;
        }

        log.error("Illegal call of InExpressionExpander.expandExpression() without IN expression.");
        return null;
    }

    private String expandInExpression(StringBuilder exprPrefixBuilder, List values) {

        String joinExpr = isNotInExpr ? ") and " : ") or ";
        StringBuilder expr = new StringBuilder(16);
        Iterator iter = values.iterator();
        int i = 0;
        boolean firstExpr = true;
        while (iter.hasNext()) {
            if (firstExpr || i % MAX_PARAMS_PER_INEXPR == 0) {
                //close previous expression and start new expression
                if (!firstExpr) {
                    expr.append(joinExpr);
                } else {
                    firstExpr = false;
                }
                expr.append(exprPrefixBuilder);
            } else {
                expr.append(", ");
            }
            expr.append(iter.next());
            i++;
        }

        expr.append(')');// close for last in expression

        return expr.toString();
    }

    /**
     * Method extract last expression parsed by space from toWalkQuery and remove it from toWalkQuery;<br/>
     * If expression has brackets it will return al content between brackets and it will add additional space to adjust splitting by space.
     *
     * @return last expression from toWalkQuery
     */
    private String extractLastExpression() {
        return extractLastExpression(true);
    }

    /**
     * Method extract last expression parsed by space from toWalkQuery, remove it from toWalkQuery if is consume = true;<br/>
     * If expression has brackets it will return al content between brackets and it will add additional space to adjust splitting by space.
     *
     * @param consum if true  the method will extract and remove last expression from toWalkQuery
     * @return last expression from toWalkQuery
     */
    private String extractLastExpression(final boolean consum) {
        int lastIndex = this.toWalkQuery.length() - 1;
        String lastExpr;
        int exprSeparatorIndex = this.toWalkQuery.lastIndexOf(" ");
        if (lastIndex == exprSeparatorIndex) { //remove last space from the end
            this.toWalkQuery.delete(exprSeparatorIndex, this.toWalkQuery.length());
            return extractLastExpression(consum);
        } else {
            lastExpr = this.toWalkQuery.substring(exprSeparatorIndex + 1, this.toWalkQuery.length());

            if (lastExpr.length() > 1) {
                if (lastExpr.endsWith(")")) {
                    //if parens are closed at the end we need to find where it is open
                    int opensParens = 0;
                    int closedParens = 0;
                    int startExprIndex = -1;

                    char c;
                    for (int i = lastExpr.length() - 1; i > -1; i--) {
                        c = lastExpr.charAt(i);
                        if (c == ')') {
                            closedParens++;
                        } else if (c == '(') {
                            opensParens++;
                        }

                        if (closedParens == opensParens) {
                            startExprIndex = i;
                            break;
                        }
                    }

                    if (startExprIndex > -1) {
                        lastExpr = lastExpr.substring(startExprIndex, lastExpr.length());
                        exprSeparatorIndex = exprSeparatorIndex + startExprIndex
                                + 1; // +1 because separator is not space and don't must be deleted
                    }
                } else if (lastExpr.contains("(")) {
                    int parentsIndex = exprSeparatorIndex + lastExpr.indexOf('(') + 1;
                    this.toWalkQuery.replace(parentsIndex, parentsIndex + 1, " ( ");
                    return extractLastExpression(consum);
                }
            }

            if (consum) {
                this.toWalkQuery.delete(exprSeparatorIndex, this.toWalkQuery.length());
            }
        }

        if (consum) {
            stackExpr.push(lastExpr);
        }

        return lastExpr;
    }

    private String extractColumnForInExpression() {
        String column = extractLastExpression();

        String beforeColumn = extractLastExpression(false);
        long pointIndx = beforeColumn.lastIndexOf('.');
        if (pointIndx > -1) {
            if (pointIndx == (beforeColumn.length() - 1)) {
                throw new QueryException(
                        "Invalid column format: " + beforeColumn + ' ' + column
                                + " . Remove space from column!");
            }
        }
        return column;
    }

    private String getBeforeExpression() {
        return this.toWalkQuery + " (";
    }

    private String getAfterExpression() {
        if (StringHelper.getFirstNonWhitespaceCharacter(afterPlaceholder) == ')') {
            return afterPlaceholder;
        }
        return afterPlaceholder + ") ";
    }
}

我很乐意接受任何改进此解决方案的建议。

- Vasile Bors

---

虽然这个链接可能回答了问题，但最好在此处包含答案的基本部分并提供参考链接。如果链接页面更改，仅具链接的答案可能变得无效。- 来自评论 - piet.t

谢谢您的建议。 - Vasile Bors